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  • Articles  (432)
  • Chemical Engineering  (389)
  • adsorption  (43)
  • Cell & Developmental Biology
  • Condensed Matter: Electronic Properties, etc.
  • Inorganic Chemistry
  • Magnetism
  • Strong Interactions
  • Surface physics, nanoscale physics, low-dimensional systems
  • ddc:650
  • 2015-2019
  • 1995-1999  (432)
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (432)
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  • Articles  (432)
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  • 1
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation of boundary lubricated interfaces (1999)
    Springer
    Journal of computer-aided materials design 6 (1999), S. 69-80 
    Details
    ISSN: 1573-4900
    Keywords: adsorption ; friction ; lubrication ; tribological system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A molecular dynamics simulation study of friction in boundary lubrication was conducted in order to investigate the atomic-scale behavior of lubricant molecules during sliding motion. The simulated system consisted of two silicon (001) semi-infinite substrates lubricated by a three-layer film of dodecane. Silicon was modeled using the Stillinger–Weber potential, and the dodecane with the Consistent Force Field function; a novel scheme was used to generate the silicon–dodecane interaction potentials. The simulations show that dodecane molecules strongly prefer to adsorb into the ledges on the silicon surface. The orientation of the adsorbed molecules depends, however, on the concentration of the lubricant at the surface, showing a tendency to stand up at high lubricant concentrations. In sliding, the dodecane layers adsorbed on the surfaces behave as a solid, whereas the middle layer exhibits liquid-like characteristics. The friction coefficient of this well-lubricated case was calculated to be 0.08.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008658828194
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  • 2
    Electronic Resource
    Electronic Resource
    Observation of a Sharp Transition in Contact Angle in the Wetting of Graphite by Solid Pb-Ni Alloys (1999)
    Springer
    Interface science 7 (1999), S. 173-180 
    Details
    ISSN: 1573-2746
    Keywords: contact angle transition ; wetting ; interfacial energy ; solid pb-Ni/graphite system ; adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The wetting of Pb-Ni crystals on graphite has been observed at 558 K in a Scanning Auger Microprobe. Samples were prepared so as to produce 10 μm crystals of Pb with Ni contents increasing from 0 to 0.3 wt% along one axis of the graphite substrate. In the low Ni region, the contact angle was found to decrease slowly from 119° to 98° with increasing Ni content. In the region of high Ni content, a constant contact angle of 83° was measured. In between, crystals with contact angles of 98° and 83° were observed to coexist, near the limit of solubility of Ni in Pb, indicating the presence of a first order transition in contact angle. The continuous decrease in contact angle, in the low Ni region, is due to Ni adsorption at the Pb-graphite interface, which leads to a decrease in interfacial energy. The constant contact angle in the high Ni region is associated with the precipitation of a Ni-rich phase. Various hypotheses are advanced to account for the first order transition in contact angle as a function of Ni concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008779501606
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of Porous Carbonaceous Sorbents Using High Pressure CO2 Adsorption Data (1998)
    Springer
    Journal of porous materials 5 (1998), S. 275-287 
    Details
    ISSN: 1573-4854
    Keywords: activated carbons ; adsorption ; characterization ; Dubinin-Radushkevich ; carbon dioxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this paper we present adsorption isotherms of carbon dioxide on five different activated carbons from CHEMVIRON CARBON Belgium (Centaur HSV, BPL 410, F30-470, WS 42, Reactivated) and on a carbon molecular sieve from BERGBAU FORSCHUNG Gmbh (CMS II). The temperature is 303 K and the pressure ranges from 100 kPa up to 4000 kPa. Such conditions correspond to relative pressures ranging from 0.01 to 0.5. We also provide, for the same six sorbents, the nitrogen isotherms at 77 K (pressure: 0.001 to 100 kPa, relative pressure: 10-5 to 1). A theoretical treatment based on the Dubinin-Radushkevich and Stoeckli concept is presented and applied to the experimental results in order to obtain the micropore size distribution function (considered as Gaussian) of each sorbent. Using the CO2 data, it is possible to point out important structural differences between the six carbons. The theoretical treatment provides micropore size distribution functions in agreement with what is physically expected. Using N2 data, the structural differences are not so well marked. As a consequence, the structural parameters provided by the theoretical treatment are not reliable: except for the total micropore volume, they fluctuate strongly when changing the relative pressure domain of the used data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009638406224
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  • 4
    Electronic Resource
    Electronic Resource
    Structure and molecular motion of poly(ethylene oxide) chains adsorbed on a silica-tethered poly(methyl methacrylate) by the spin label method (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 412-419 
    Details
    ISSN: 1435-1536
    Keywords: Key words poly(ethylene oxide) ; silica-tethered poly(methyl methacrylate) ; adsorption ; spin-label ; molecular motion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  The spin-label method was used to study the structure and molecular motion of poly(ethylene oxide) (PEO) chains adsorbed on a silica-tethered poly(methyl methacrylate) (PMMA). Spin-labelled PEO with a narrow molecular weight distribution, having number averaged molecular weight (M N)=6.0×103, was adsorbed on the surface of the silica-tethered PMMA with various grafting ratios in carbon tetrachloride solution at 35 °C. ESR spectra were measured at various temperatures after the samples were completely dried. The ESR spectra are composed of two spectra arising from spin-labels attached to “train” and “tail” segments, which are strongly and weakly interacted with the silica surface, respectively. The fractional amount of the “tail” segments increases extremely with the grafting ratio of PMMA. Molecular mobility of the PEO chains estimated from the temperature dependence of the ESR spectra also decreases significantly with the grafting ratio of PMMA. Structure and molecular motion of the PMMA chains tethered on the silica were also studied using the spin-labelled PMMA. Consequently, parts of the PEO segments penetrate into the PMMA chains and is adsorbed on the silica surface (“train” segments), whereas parts of the PMMA segments protrude from the surface. The other PEO segments are entangled with the tethered PMMA chains (“tail” segments).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050260
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  • 5
    Electronic Resource
    Electronic Resource
    The interface air/water of n-dodecanephosphonic acid solutions (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 52-58 
    Details
    ISSN: 1435-1536
    Keywords: Key words Dodecanephosphonic acid ; soluble monolayer ; air/water interface ; evaporation ; adsorption ; ion-selective electrodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  The air/water interface of the system n-dodecanephosphonic acid (H2DP)–water was studied by surface tension, ion-selective electrodes and evaporation in an electrobalance. The combination of surface tension and ion-selective electrodes measurements enables to study the adsorption of soluble surfactants above the cmc using the Gibbs’ equation. H2DP formed a nonideal monolayer at the air/water interface with A molec=0.995 nm2 below the cmc. Above the cmc there was a reduction in adsorption giving A molec=6.32 nm2, which remained almost constant in the explored concentration range. This adsorption reduction may be due to a change composition on micellization, or to a thermodynamic advantage of micellization on adsorption. The reduction in the evaporation rate of water was mainly due to the reduction of the water activity, caused by the presence of solutes in bulk. This is because the strong changes in the surface coverage did not have significant influence on the evaporation rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050208
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis of temperature-sensitive micron-sized monodispersed composite polymer particles and its application as a carrier for biomolecules (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 470-475 
    Details
    ISSN: 1435-1536
    Keywords: Key words Composite particle ; temperature-sensitive ; biomolecules ; specific activity ; adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Temperature-sensitive micron-sized monodispersed composite polymer particles were prepared by seeded copolymerization of dimethylaminoethyl methacrylate and ethylene glycol dimethacrylate with 1.77 μm-sized monodispersed polystyrene seed particles. The change in surface property at temperature above and below 35 °C was examined by differential scanning calorimetry, trypsin activity and the adsorption/ desorption behaviors of low molecular weight cationic emulsifier as well as biomolecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050268
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  • 7
    Electronic Resource
    Electronic Resource
    Thermodynamic study on the adsorption and micelle formation of long chain alkyltrimethylammonium chlorides (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 595-600 
    Details
    ISSN: 1435-1536
    Keywords: Key words Surface tension ; adsorption ; micelle ; entropy ; energy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The surface tension of aqueous solutions of tetradecyl-trimethylammonium chloride (TTAC) and decyltrimethylammonium chloride (DeTAC) were measured as a function of temperature at concentrations below and above the critical micelle concentration under atmospheric pressure. The entropy and energy of adsorption from the monomeric state and from the micellar state and also the entropy and energy of micelle formation for TTAC were evaluated and compared with those of dodecyltrimethyl-ammonium chloride (DTAC). The values of ΔM W s and ΔM W u for TTAC and DTAC systems show that the micelle formation is driven by the entropy at low temperatures and by the energy at high temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050286
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  • 8
    Electronic Resource
    Electronic Resource
    Pore Structure Tailoring of Pillared Clays with Cation Doping Techniques (1998)
    Springer
    Journal of porous materials 5 (1998), S. 227-239 
    Details
    ISSN: 1573-4854
    Keywords: pillared clays ; cation doping ; pore structure tailoring ; adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Techniques and mechanism of doping controlled amounts of various cations into pillared clays without causing precipitation or damages to the pillared layered structures are reviewed and discussed. Transition metals of great interest in catalysis can be doped in the micropores of pillared clay in ionic forms by a two-step process. The micropore structures and surface nature of pillared clays are altered by the introduced cations, and this results in a significant improvement in adsorption properties of the clays. Adsorption of water, air components and organic vapors on cation-doped pillared clays were studied. The effects of the amount and species of cations on the pore structure and adsorption behavior are discussed. It is demonstrated that the presence of doped Ca2+ ions can effectively aides the control of modification of the pillared clays of large pore openings. Controlled cation doping is a simple and powerful tool for improving the adsorption properties of pillared clay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009682221245
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular Sieves, Multifunctional Microporous Materials in Organic Synthesis (1998)
    Springer
    Journal of porous materials 5 (1998), S. 289-303 
    Details
    ISSN: 1573-4854
    Keywords: zeolites ; design ; catalysis ; shape selectivity ; adsorption ; properties ; application
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Zeolites and molecular sieves are microporous materials with an increasing number of applications. Established applications of molecular sieves are in the field of oil refining processes, selective adsorption and ion exchange. Nowadays, zeolites come to the fore as clean, selective and recyclable catalysts in petrochemistry, e.g., in aromatic alkylation. Zeolites are considered to have a high potential for the synthesis of commodities and fine chemicals due to their molecular sized pores. Nevertheless, only a few commercial applications in fine chemical synthesis are known. Based on the essential criteria, extracted from the organic reaction under consideration, some of the potential pitfalls in selecting and screening zeolites as potential catalysts are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009690423062
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of base oil oxidation on scuffing (1998)
    Springer
    Tribology letters 4 (1998), S. 59-66 
    Details
    ISSN: 1573-2711
    Keywords: scuffing ; oil oxidation ; base oils ; adsorption ; Fourier transform infrared spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this work, the effect of base oil oxidation on scuffing was investigated. It was found that under mixed lubrication conditions there is a direct relationship between the level of base oil oxidation and the onset of scuffing, i.e., the greater the oxidation the lower the likelihood of scuffing. An oxidised base oil forms, among other products, carboxylic acids, which reduce scuffing failure in comparison with the parent oil. This was confirmed by the addition of a carboxylic acid directly to the base oil operating under the same mixed lubrication conditions. The removal of the carboxylic acids from the oxidised oil via column chromatography resulted in a scuffing failure performance equivalent to the parent oil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019126415557
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  • 11
    Electronic Resource
    Electronic Resource
    Polyoxyethylene di-phosphonates as dispersing agents (1997)
    Springer
    Colloid & polymer science 105 (1997), S. 6-10 
    Details
    ISSN: 1435-1536
    Keywords: Colloidal aqueous suspensions ; adsorption ; rheology ; polyethylene oxide ; phosphonate ; calcium carbonate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract New polymeric dispersing agents designed to stabilize and lower the viscosity of aqueous mineral suspensions have been synthesized and studied. These dispersants are made of a non-ionic hydrosoluble polymer (polyethylene oxide) with a functional group (diphosphonate) having a strong affinity for the mineral surfaces attached at one end of the macromolecular chains. This molecular architecture allows a brush-like adsorption at the solid surface which differs from conventional homopolymer dispersants such as polyacrylates. The adsorption of these dispersants onto calcium carbonate as a model mineral and the rheological behavior of concentrated aqueous colloidal dispersions of CaCO3 particles were studied. Strong adsorption by the polymer chain-end provides an enhanced colloidal stability of the suspensions of CaCO3 particles. The addition of the dispersing polymer causes a deaggregation of the initially flocculated CaCO3 particles, which results in a drastic reduction of the viscosity of the concentrated suspensions. Thus, the viscosity of a 20 wt% CaCO3 suspension in water at pH=11 is lowered to 2 mPa s upon the addition of a low concentration of polymer. Comparison with polyacrylate dispersants shows the advantages of such a diblock macromolecular structure with a non-ionic polymeric part at high solid contents and high ionic strengths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01188916
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  • 12
    Electronic Resource
    Electronic Resource
    The effect of S, N, and C on the oxidation of Ni-20%Cr and Fe-20%Cr (1997)
    Springer
    Oxidation of metals 47 (1997), S. 495-506 
    Details
    ISSN: 1573-4889
    Keywords: chromia-forming alloys ; nonmetallic-element effects ; segregation ; adsorption ; surface compounds ; nucleation ; oxide grain boundaries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The effect of S, N, and C on the oxidation of Ni 20%Cr and Fe-20%Cr was investigated by two approaches (i) using AES and LEED following oxide nucleation and growth under UHV conditions and (ii) by thermogravimetry and subsequent SEM analysis, under conditions where only adsorption/segregation of these elements and congregation of Cr occurred. Sulfur retards nucleation, inhibits lateral growth, and leads to a coarse-grained oxide with a wide network of ridges at the grain boundaries—the growth rate decreases with increasing sulfur activity. Nitrogen and carbon or rather the cosegregated Cr promote the nucleation of C2O3, which leads to many grains and grain boundaries in the oxide layer, accelerated growth and a sponge-like morphology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02134788
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  • 13
    Electronic Resource
    Electronic Resource
    Modification of the Porosity of Pillared Clays by Carbon Deposition II. Hydrocarbon Cracking (1997)
    Springer
    Journal of porous materials 4 (1997), S. 5-15 
    Details
    ISSN: 1573-4854
    Keywords: pillared clay ; pore size modification ; adsorption ; cracking ; carbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract To enhance the adsorption selectivity of pillared clays an attempt is made to modify the initial pore size by a controlled deposition of carbon. Cracking of hydrocarbons in the pores of the pillared clay results in coke deposits which can alter the pore size. Based on the evaluation of the amount of coke, the coke density, the decrease in micropore volume, changes in the micropore size distribution and the acidity it was possible to distinguish between pore-blocking, pore-filling and pore-narrowing effects. The modification mechanisms strongly depend on the initial porous structure, the acidity (Brönsted/Lewis), the cracking conditions (static or flow) and the hydrocarbons used. The carbon deposition results in a decrease in pore volume due to pore-filling (Ti-PILC) and pore-blocking (Al-PILC) without achieving a controlled pore-narrowing but some indications for pore-entrance narrowing were found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009663020550
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  • 14
    Electronic Resource
    Electronic Resource
    Humidity Sensor Characteristics of Woodceramics (1997)
    Springer
    Journal of porous materials 4 (1997), S. 277-280 
    Details
    ISSN: 1573-4854
    Keywords: woodceramics ; porous carbon ; adsorption ; humidity sensor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The humidity sensor characteristics of Woodceramics were investigated. The Woodceramics used in this experiment were prepared at 650–900°C. The size of specimens selected was 1 × 1 × 10 mm . One was used as-cut and the other was polished. Above 700°C, the resistance of the specimen was below 50 Ω and the decrease of resistance with increasing relative humidity was small. The specimen prepared at 650°C had a resistance of about 1 kΩ. The resistance of as-cut specimens decreased with increase in relative humidity, but that of the polished specimen did not change significantly. The difference between as-cut and polished samples was explained by the differences in surface micro-structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009677306740
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  • 15
    Electronic Resource
    Electronic Resource
    Adsorption of cationic polyelectrolyte onto a model carboxylic latex and the influence of adsorbed polycation on the charge regulation at the latex surface (1997)
    Springer
    Colloid & polymer science 275 (1997), S. 655-660 
    Details
    ISSN: 1435-1536
    Keywords: Key words Polyelectrolyte ; adsorption ; latex ; surface charge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Adsorption of a well-characterized cationic polyacrylamide (CPAM) onto the surface of a model colloid (monodisperse polystyrene latex with carboxylic functional groups) was studied over a wide range of pH (4–9) and KCl concentration (c s =10-3–0.3 M). The surface charge density of the latex particles with and without adsorbed CPAM was also measured over the same range of electrolyte compositions. The adsorbed amount of CPAM increases with increase in c s and pH. The polyelectrolyte adsorption alters substantially the surface charge density of the latex particles as compared to the polymer-free case. A large overcompensation of the surface charge by the adsorbed polyelectrolyte is established at high c s and low pH. A qualitative explanation of the observed features is put forward.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050132
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  • 16
    Electronic Resource
    Electronic Resource
    Effect of surfactants on zeta potential and static electricity of viscose fibres (1997)
    Springer
    Colloid & polymer science 105 (1997), S. 72-74 
    Details
    ISSN: 1435-1536
    Keywords: Zeta potential ; static electricity ; surfactants ; viscose fibres ; adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Viscose fibres were finished with a blend of a nonionic fatty acid ethoxylate and a quarternary ammonium derivative. Zeta potential and static charging were investigated as a function of a cationic compound. There is strong evidence that the charging of the viscose fibres depends on the chemical nature of the surfactants side-groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01188928
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  • 17
    Electronic Resource
    Electronic Resource
    Nonionic surfactants in cylindrical hydrophilic pores (1997)
    Springer
    Colloid & polymer science 105 (1997), S. 91-95 
    Details
    ISSN: 1435-1536
    Keywords: Surfactant ; adsorption ; pore ; curvature ; mean field ; lattice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A mean field lattice (MFL) theory has been used to study the adsorption behaviour of nonionic surfactants in hydrophilic cylindrical pores. The theory predicts that with decreasing pore radius the absorbed amount decreases. Moreover, the step in the adsorption isotherm, which is a first-order phase transition in the mean field approximation, shifts to lower concentrations. Both effects have been observed in experiments. When an adsorbed layer is curved from convex (rod) to concave (pore) at constant area, the volume of the layer decreases. As a consequence, the stability of the layer increases and the adsorbed amount decreases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01188932
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  • 18
    Electronic Resource
    Electronic Resource
    Adsorption of multivalent ions on charged Langmuir monolayers (1997)
    Springer
    Colloid & polymer science 105 (1997), S. 118-125 
    Details
    ISSN: 1435-1536
    Keywords: Langmuir monolayer ; adsorption ; X-ray reflectivity ; surface potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We have investigated the interaction between a Langmuir monolayer of C20H41NH2, a long-chain fatty amine and large, multivalent, heteropolyanions (phosphotungstic acid, PTA for short) dissolved in the aqueous subphase. By using X-ray reflectivity, surface pressure and surface potential measurements, we show that the adsorption is controlled by the electrostatic interaction between the PTA molecules and the amine film. At basic pH, the amine groups are not charged and no adsorption occurs. On the contrary, at acidic pH, the amines are positively charged. The surface pressure isotherms are markedly different in presence of PTA and the surface potential measurements reveal a reversal of the surface polarity. X-ray reflectivity gives a microscopic picture of the interfacial layer. The PTA anions are adsorbed onto the charged amine head groups as a monolayer or at most a bilayer. Changing the surface density of amines allows to control the total amount of PTA adsorbed and to vary the inorganic layer thickness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01188937
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  • 19
    Electronic Resource
    Electronic Resource
    Phase transitions in adsorption layers: comparison with Langmuir monolayers (1997)
    Springer
    Colloid & polymer science 105 (1997), S. 130-137 
    Details
    ISSN: 1435-1536
    Keywords: Phase transition ; adsorption ; isotherm ; Brewster angle microscopy ; Gibbs monolayer ; Langmuir monolayer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The adsorption layers of aqueous solutions of N-dodecyl-γ-hydroxy-butyric acid amide show a first-order phase transition between a fluid-like low-density phase and a condensed phase. Two-dimensional domains are formed which were visualized by Brewster angle microscopy. Theπ- A isotherms of the Langmuir monolayers show the wellknown plateau region with the critical surface pressure as the starting point for the first-order phase transition in the Langmuir monolayer. The measurements ofπ-t adsorption kinetics revealed a conspicuous inflection point at the same critical surface pressure. This inflection point is also related to the start of a first-order phase transition in the Gibbs monolayer. The results of theσ-logc isotherms are interpreted by the Frumkin's equation of state. Based on the calculated interaction parameters, the formation of a condensed phase in Gibbs monolayers is concluded. Thermodynamic behavior and morphological features of the Langmuir and Gibbs monolayers were compared and the similarities in morphology and thermodynamically properties of spread and of adsorbed molecules at the air-water interface demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01188939
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  • 20
    Electronic Resource
    Electronic Resource
    Polyelectrolyte-surfactant interactions at interfaces (1997)
    Springer
    Colloid & polymer science 106 (1997), S. 24-33 
    Details
    ISSN: 1435-1536
    Keywords: Polyelectrolyte-surfactant association ; surface forces ; steric forces ; critical association concentration ; adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Interactions between negatively charged surfaces coated with cationic polyelectrolytes across solutions containing an anionic surfactant, sodium dodecyl sulphate (SDS) have been studied. Polyelectrolytes with charge densities between 100% and 10%, counted per monomer unit, were used. At low ionic strength the polyelectrolytes adsorb in a flat conformation to neutralize the negative mica surface charge. The higher the linear charge density of the polyelectrolyte, the thinner adsorbed layers are obtained. In no case could any desorption be detected when the polyelectrolyte containing solution was replaced with an aqueous polyelectrolyte-free solution. The presence of SDS at concentrations considerably below the critical micellar concentration (cmc) does in all cases result in a recharging and a considerable swelling of the adsorbed layer. This is due to a cooperative association of surfactants in the preadsorbed polyelectrolyte layer. In case of the 100% charged PCMA, the force versus distance profile displays clear oscillations. We interpret these oscillations as being caused by the spatial arrangement of SDS micelles induced by the polyelectrolyte. The oscillations in the force curve remain as the SDS concentration is increased to twice the cmc. No similar oscillations in the force distance curve are observed when the surfaces are precoated with less charged polyelectrolytes. In these cases a strong swelling of the polyelectrolyte layer is observed once the surfactant concentration reaches a critical value (well below the cmc).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01189486
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    Rheological properties of silica suspensions in the presence of polymer (1997)
    Springer
    Colloid & polymer science 106 (1997), S. 180-182 
    Details
    ISSN: 1435-1536
    Keywords: Rheology ; suspension ; adsorption ; polystyrene ; depletion flocculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Storage moduli (G′) of hydrophilic and hydrophobic silica suspensions in trans-decalin and in trans-decalin solutions of polystyrene (PS) have been measured by taking account of PS adsorption. PS were adsorbed on the hydrophilic silica. TheG′ values of the hydrophilic suspensions in the presence of low molecular weight PS are similar to those without PS and they are larger than those in the presence of higher molecular weight PS. On the other hand, any PS chains cannot adsorb on the hydrophobic silica particles. TheG′ values of all hydrophobic suspensions are higher than that in trans-decalin due to depletion flocculation and they are two orders of magnitude larger than those for the hydrophilic silica suspensions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01189516
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    The Uses of Polynuclear Metal Complexes to Develop Designed Dispersions of Supported Metal Oxides: Part II. Catalytic Properties (1997)
    Springer
    Interface science 5 (1997), S. 199-206 
    Details
    ISSN: 1573-2746
    Keywords: catalysis ; adsorption ; transition metal complexes ; designed dispersions ; metal oxide coatings ; infrared spectroscopy ; thermogravimetric analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract In many catalytic reactions, the configuration, dispersion andensemble size of the supported catalytic species have a significant impacton the activity, selectivity and product distribution of the catalyst. Byusing the method of molecular design, it becomes possible to fundamentallyoptimize these catalytic reactions, eliminating side reactions and improvingthe activity or selectivity of the catalyst, provided that the detailedreaction mechanisms and the structural dependencies are known. In thismanuscript, several examples are presented that illustrate the dramaticeffect of the ensemble size of the supported catalytic species on thecatalytic behavior. It is evidenced how supported metal oxides may beprepared to have quite different catalytic properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008621629413
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    The Uses of Polynuclear Metal Complexes to Develop Designed Dispersions of Supported Metal Oxides: Part I. Synthesis and Characterization (1997)
    Springer
    Interface science 5 (1997), S. 169-197 
    Details
    ISSN: 1573-2746
    Keywords: catalysis ; adsorption ; transition metal complexes ; designed dispersions ; metal oxide coatings ; infrared spectroscopy ; thermogravimetric analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract One way to design a catalyst begins with a consideration of thereaction mechanism to the desired product so that only the chemistryrequired of that mechanism will be present on the surface. The reactionmechanism will suggest the structure(s) to be developed on the surface whichshould be stabilized against changes during operation. We believe that thisideal may be approached by decorating surfaces or porous powders with amonolayer of metal complexes having the desired structures. These complexesmay be partially decomposed to develop a high dispersion of the supportedmetal oxide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008669528505
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    Ellipsometry and TIRF Studies of Adsorption Processes in Parenteral Drug Delivery (1997)
    Springer
    Interface science 5 (1997), S. 159-167 
    Details
    ISSN: 1573-2746
    Keywords: adsorption ; ellipsometry ; opsonins ; PEG ; phospholipids ; polymers ; proteins ; TIRF
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Ellipsometry and total internal reflection fluorescence spectroscopy(TIRF) were used for investigating adsorption processes of relevance forparenteral administration of colloidal drug carriers. Emphasis is put ondiscussing the effects of both protein and surface properties on theadsorption of serum proteins at phospholipid and other surfaces.Furthermore, the adsorption from multicomponent protein systems, such asblood, is addressed, and both competitive and associative adsorptionphenomena discussed. The correlation between effects of the drug carriersurface properties on the serum protein adsorption and the circulation timeand tissue distribution of colloidal drug carriers is also addressed.Finally, the potential of ellipsometry in another adsorption process ofmajor importance for phagocytosis, i.e., the adsorption of colloidalparticles to macroscopic or mesoscopic surfaces, is indicated byinvestigations of the adsorption of oil-in-water emulsion droplets atsilica.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008613411666
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    Nonlinear kinetics of oxygen and nitrogen sorption on carbon molecular sieves (1996)
    Springer
    Journal of porous materials 3 (1996), S. 5-16 
    Details
    ISSN: 1573-4854
    Keywords: carbon molecular sieve ; adsorption ; adsorption kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Equilibrium and kinetics of oxygen and nitrogen sorption in two different carbon molecular sieves (CMS) have been modeled. In both CMS materials, equilibrium characteristics are adequately described by the Langmuir model. However, for kinetics of sorption, one CMS followed classic Fickian diffusion, while the other sample did not. A mathematical model was developed which accurately describes both pure component as well as binary uptakes in both materials. Simple manipulation of the boundary condition of the diffusion process allows the model to accurately predict both Fickian and surface barrier diffusion. All parameters needed to estimate binary uptake rates are obtained from pure component uptakes and isotherms. In addition, the model predicts both pure component and binary diffusion rates with diffusion coefficients which are not concentration dependent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01135356
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    Modification of the porosity of pillared clays by carbon deposition. I. Polymer carbonization (1996)
    Springer
    Journal of porous materials 3 (1996), S. 257-266 
    Details
    ISSN: 1573-4854
    Keywords: pillared clay ; pore size modification ; adsorption ; polymers ; carbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In order to use pillared clays (PILC) for selective adsorption, further modifications of the porous structure are necessary. The deposition of carbon residues onto the porous structure of pillared clays by the carbonization of polymers (polyvinylalcohol) was proposed to achieve a controlled modification of the pore size. Ti and Al-pillared clays (calcined and non-calcined) were impregnated with PVA (different grades and different concentrations and subsequently carbonized to form carbon phases. The effect of the carbon deposits on the porosity of Ti- and Al-PILC is discussed in terms of pore-blocking, pore-filling and pore-narrowing. The deposition of carbon using PVA resulted in a complete pore-blocking for Al-PILC and in a narrowing of the pore size distribution for Ti-PILC, without achieving a controlled pore-narrowing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01137915
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    Adsorption of polyacrylic acid on hydrophobic and hydrophilic surfaces (1996)
    Springer
    Colloid & polymer science 274 (1996), S. 548-554 
    Details
    ISSN: 1435-1536
    Keywords: Polyacrylic acid ; γ-Al2O3 ; mercury surface ; adsorption ; voltammetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this paper the adsorption of polyacrylic acid (MW=5000) on the hydrophobic mercury surface and on the hydrophilic γ-Al2O3 surface at pH=3–4 in 0.55 M sodium chloride solution was investigated. Measurements of change of the double layer capacitance by phase selective a.c. voltammetry were used for determination of the adsorption of polyacrylic acid on the mercury electrode. The same method was used for the determination of the polyacrylic acid remaining in the solution after the adsorption on hydrophilic particles (γ-Al2O3 particles). The results obtained for adsorption of polyacrylic acid were compared to the results of the adsorption of humic substance of similar molecular weight under similar experimental conditions. The study has shown that polyacrylic acid in acidic solution is strongly adsorbed on the mercury surface, which is comparable to the adsorption of humic substance on the mercury surface. At the same time, the adsorption/deposition of polyacrylic acid on the γ-Al2O3 surface is weaker compared to humic acid, indicating at a smaller degree of interaction of polyacrylic acid with aluminium ions and with hydrophilic surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655230
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  • 28
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    Van der Waals attraction between Stöber silica particles in a binary solvent system (1996)
    Springer
    Colloid & polymer science 274 (1996), S. 779-787 
    Details
    ISSN: 1435-1536
    Keywords: Silica particles ; colloid stability ; Hamaker constant ; van der Waals potential ; adsorption ; rheology ; SAXS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Hydrophilic Stöber silica particles are stable in ethanol, but flocculation may be induced by the addition of sufficient cyclohexane. Low-shear rheological measurements indicated non-Newtonian behaviour beyond the critical cyclohexane concentration. The thickness and composition of the solvation layer around the particles were calculated from the adsorption excess isotherm on the basis of a multilayer adsorption model. The composition dependences of the Hamaker constants of the dispersion medium and the adsorption layer were obtained from optical dispersion measurements. A single-sheet, hard-sphere model predicted a weak van der Waals attraction in the ethanolic regime, but a strong attraction in the cyclohexane-rich region, in good accordance with the rheological properties of the dispersions and visual observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00654674
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    Interaction of sodium dodecylsulfate (SDS) with homoionic montmorillonites: adsorption isotherms and metal-ion release (1996)
    Springer
    Colloid & polymer science 274 (1996), S. 966-973 
    Details
    ISSN: 1435-1536
    Keywords: Sodium dodecylsulfate ; adsorption ; precipitation ; montmorillonite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The interaction of dodecylsulfate anions (DS−) with homoionic Ca-, Mg-, Ni-, Cu-, Cd-, Pb- and Fe-montmorillonites were investigated. Mg- and Cd-montmorillonite do not adsorb DS−, and an anion exchange at the edges of the clay mineral does not take place. Three different adsorption processes are identified on the other montmorillonites: i) Fe-montmorillonite is covered with amorphous iron hydroxide, and DS−-anions are bound at positively charged sites. ii) On Ca- and Pb-montmorillonite DS− is precipitated as Me(DS)2. iii) On Ni- and Cu-montmorillonite DS− forms ion pairs with the cations on the surface. In all cases DS− is not bound above the CMC but the metal ions are mobilized from the surface either by solubilization of the precipitates or by formation of mixed micelles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00656626
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    Adsorption behaviors of emulsifiers and biomolecules on temperaturesensitive polymer particles (1996)
    Springer
    Colloid & polymer science 274 (1996), S. 112-116 
    Details
    ISSN: 1435-1536
    Keywords: Temperature-sensitive ; emulsifier ; biomolecules ; adsorption ; surface
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Adsorption and desorption behaviours of emulsifiers and biomolecules on the two kinds of temperature-sensitive composite polymer particles were compared. One (I) was produced by seeded emulsion copolymerization of dimethylaminoethyl methacrylate and ethylene glycol dimethacrylate with 0.17 μm-sized polystyrene seed particles. The other (II) was produced by seeded emulsion copolymerization of N-isopropylacrylamide (NIPAM) and N,N′-methylenebisacrylamide with 0.36 μm-sized styrene-NIPAM copolymer particles. The amount of adsorption at temperatures above each lower critical solution temperature (LCST) was found to be much higher for I than II. In both cases, at temperatures below the LCST, almost all lactalbumin hydrolysate molecules adsorbed above the LCST were desorbed but the desorptions of adsorbed egg albumin and lysozyme molecules were not so high. The adsorption and desorption were reversible for both particles and the efficiency was better for I than II. From these results, it is concluded that the adsorption/desorption of protein onto the temperature-sensitive polymer particles is controllable by changing the temperature below and above the LCST of the shell layer and the sensitivity is based on the surface property of the composite polymer particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00663443
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    Micropore characterization using the Dubinin-Astakhov equation to analyze high pressure CO2 (273 K) adsorption data (1996)
    Springer
    Journal of porous materials 3 (1996), S. 247-255 
    Details
    ISSN: 1573-4854
    Keywords: adsorption ; micropore characterization ; activated carbon ; Dubinin-Astakhov equation ; Dubinin-Radushkevich equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The characterization of the pore structure of microporous materials is of interest because of the usefulness of these materials in many applications. Of these, the characterization of carbon adsorbents is particularly problematic because of the presence of small pores with size on the order of small molecules (micropores) along with a wide distribution of pore sizes, and their non-crystalline structure. In this paper, we present results obtained using the Dubinin-Astakhov equation to analyze data from high pressure CO2 adsorption at 273 K to characterize two sets of microporous carbons. Our results support the conclusions of previous workers that the Dubinin-Astakhov (DA) equation is able to linearize adsorption data that gives rise to curved Dubinin-Radushkevich plots. However, when applied over different ranges of relative pressure on the adsorption isotherm, the Dubinin-Astakhov plots result in different values of micropore volume and characteristic adsorption potential. Furthermore, DA analysis of CO2 (273 K) adsorption data over a wide range of pressures (10−3–22000 Tort), gives results different from DA analysis of CO2 (273 K) isotherms measured at low pressures only (10−3–830 Tort). It would appear desirable to apply the DA equation to data that reflects the entire range of micropore filling on the adsorption isotherm, as opposed to data over a limited relative pressure range. For CO2 adsorption at 273 K, this would necessitate adsorption studies at high pressures, to about 28 atm. Micropore volumes obtained in this manner, agreed with the total pore volumes determined by nitrogen (77 K) adsorption for all the activated carbons studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01137914
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    Characterisation of porous solids by simplified gas relative permeability measurements (1995)
    Springer
    Journal of porous materials 2 (1995), S. 73-77 
    Details
    ISSN: 1573-4854
    Keywords: relative permeability ; pore structure characterisation ; adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A novel design for the application of a simplified experimental procedure, capable of providing satisfactory relative permeability data for porous media at low relative pressures, is presented. The technique avoids the two-component mixing complications as well as the problems arising from the sample macroscopic inhomogeneity. The latter has been reduced with the aid of a variable pressure compaction procedure. Thus, it becomes easier to utilise the powerful relative permeability technique for the characterisation of the structure of porous solids. Emphasis is given to the combination of the relative permeability data obtained with an analytical approach based on Effective Medium Theory for the calculation of pore connectivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00486572
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    Analyses of (AD)-sorption for the estimation of pore-network dimensions and structure (1995)
    Springer
    Journal of porous materials 2 (1995), S. 191-199 
    Details
    ISSN: 1573-4854
    Keywords: adsorption ; analysis of pore structure ; estimation from sorption pore shape ; from ad-de-sorption surface area ; calculations from sorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The interpretation of pore dimensions based on physical ad-desorption analyses is central to the characterization of pore network structure. Several approaches have been proposed and are commonly employed in the analysis of physical adsorption and/or desorption to deduce the dimensions of the porous network. These approaches assume either theoretical (e.g., BET, the Halsey equation as interpreted by Pierce et al., or the more recent analyses of microporosity) or “standard” isotherms as model(s) for the sequential calculations required in estimating the pore network dimensions. Subsequent representation of the pore dimensions and the relationship between these distributions in dimension and other experimental parameters (such as catalytic activity, adsorptivity or transport); thus, depend explicitly on the model employed in the analyses. Each instrument currently available for the measurement of porous solid structure by sorption employs the same specific models for the relationship between the volume ad-desorbed and the dimensions of the porous network that is being characterized. This paper analyzes the interpretation of porous dimensions based on the sequential calculations required in the analyses. A new approach is proposed which is based on a modification to current practices reflecting Halsey's original theory for the thickness of the adsorbed layer (as a function of P/P 0). Further, the calculations of the incremental changes in the exposed surface area are discussed as they relate to pore network structure. A method is proposed to infer the differences in pore shape. Sorption data are analyzed by these new approaches, and these analyses will be compared with those approaches currently employed. Analyses based on these modified approaches provide a dramatically more consistent interpretation of the sorption data and the corresponding pore network structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00488108
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    Adsorption of whitening agents on cellulose fibers — Monitored by streaming potential measurements, calorimetry and fluorescence (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 1174-1178 
    Details
    ISSN: 1435-1536
    Keywords: Cotton fibers ; dye ; adsorption ; calorimetry ; zeta potential ; fluorescence ; degree of whiteness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Fluorescent whitening agents (FWA) are used to improve the whiteness of cellulose fabrics. It is well known but not completely understood that the fluorescence decreases (chemical and physical mechanisms of distinguishing) above a certain FWA concentrationc crit. This reduction of fluorescence correlates very well with the alteration of the adsorption process studied by calorimetry and zeta potential measurements. The results obtained by these methods indicate that the adsorption mechanism is different at concentrations below and abovec crit. The reduction of the intensity of fluorescence, the degree of whiteness and the zeta potential are caused by the adsorption of a second layer of fluorescent whitening agents. This second layer reduces the zeta potential due to a shielding effect and reduces the whiteness and fluorescence by a bathochromic shift of the reflection curves. The final effect is a reduction of the total reflection.
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    Adsorption characteristics of surfactants and phenol on modified zeolites from their aqueous solutions (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 787-792 
    Details
    ISSN: 1435-1536
    Keywords: Zeolite ; modification ; surfactant ; adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Adsorption characteristics of anion-, cation- and nonion-type surfactants and phenol from their aqueous solution on Na-Y zeolites modified by SiCl4 treatment and NA-ZSM-5 zeolites with several Si/Al ratios were measured. Surfactants used were sodium dodecylbenzenesulfonte (DBS), laurylpyridinium chloride (LPC), polyoxyethylenenonylphenylether (POENPE) and phenol. Adsorption of surfactants was enhanced by SiCl4 treatment of Na-Y, which indicates an important role of the hydrophilic-hydrophobic character in the adsorption. Adsorption isotherms were in general of Langmuir type and adsorbed amount depended on the Al/(Si+Al) or Si/Al ratio of zeolite frameworks. In case of DBS adsorption of Na-ZSM-5 series, adsorption occurred only on the outer surface due to steric hindrance. LPC adsorption abilities were observed on even hydrophilic zeolites and were ascribed to ion exchange effect. In case of phenol adsorption on hydrophobic Na-Y, the adsorption isotherm was of Type V according to BDDT classification.
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    URL: http://dx.doi.org/10.1007/BF00658758
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    Synthesis of temperature-sensitive submicron-size composite polymer particles (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 817-821 
    Details
    ISSN: 1435-1536
    Keywords: Composite particle ; temperature-sensitive ; biomolecules ; adsorption ; surface
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Temperature-sensitive composite polymer particles were prepared by seeded emulsion copolymerization of dimethylaminoethyl methacrylate and ethylene glycol dimethacrylate with 0.17 μm-sized monodispersed polystyrene seed particles. The adsorption and desorption behaviors of low molecular weight cationic emulsifier as well as albumin were examined to determine the variation of surface properties as a function of temperature below and above 35°C.
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    URL: http://dx.doi.org/10.1007/BF00657630
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    Dynamic measurements of adsorption of hydrolyzed polyacrylamide (HPAM) onto hematite (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 1028-1032 
    Details
    ISSN: 1435-1536
    Keywords: Hydrolyzed polyacrylamide ; hematite ; adsorption ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The adsorption measurements of hydrolyzed polyacrylamide (HPAM) onto hematite suspension are carried out to study the dynamics of the polymer adsorption onto the suspension particles and to investigate the mode of the polymer adsorption. The polymer is found to show much affinity for the adsorption because of the opposite charges possessed by the polymeric flocculant and the suspension particles. Various adsorption parameters such as adsorption coefficient, the rate constants for the adsorption and desorption, are evaluated with the help of a recently proposed kinetic scheme. It is found that the extent of adsorption and the adsorption rate are adequately affected by increasing the pH of the suspension while, unexpectedly, the adsorption is found to show only a marginal increase on addition of Na2SO4. Both the amount of the adsorbed polymer and the adsorption rate are also found to increase with the degree of hydrolysis of the polyelectrolyte.
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    URL: http://dx.doi.org/10.1007/BF00657669
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    Compatibility of poly(ethylene 2,6-naphthalate) and poly(butylene 2,6-naphthalate) blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1807-1810 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Blends prepared from poly(ethylene 2,6-naphthalate) (PEN) and poly(butylene 2,6-naphthalate) (PBN) show only partial miscibility judged from their glass transition temperatures. Two distinct mechanical behaviors are observed: brittle for the blends 〈 20 wt% of PBN, while ductile 〉 20 wt% of PBN. The experimental modulus and strength values of the blends are within the predicted values according to Kleiner and Paul models, respectively. This means that PEN/PBN blends are somewhat compatible based on their tensile properties. Especially for 20 wt% of PBN blend, the high modulus and strength are observed. The viscosity of the blend is high, which may imply a somewhat entangled morphology in the amorphous state.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352210
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    Masthead (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352301
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    Effects of mixing porcedures on properties of compatibilized polypropylene/nylon 6 blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1821-1833 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The paper consides the effects of compatibilization with maleic anhydride grafted polypropylene (PP-g-MAH) on the propertie of immiscible blends of polypropylene (PP) and nylon 6 (N6). We prepared the blends by three different mixing processes; single-step blending, two-step blending with reactive premixing, and two-step blending with nonreactive premixing, to determine the effective mixiing process for fine morphological structure thermal stability, and mechanical properties. Dynamic melt reheological properties were measured to examine the modification of elastic properties by the compatibilizer. In addtion, thermal analysis was also carried out to detect the change in crystallization and thereby to probe the degree of compatibilizaton. The results show that compatibilized blends prepared by teh single-step process exhibit improved phase morphology, thermal stability, and mechanical properties for dried conditions, compared with other blend types. Finally, the water absorption test indicates that the added compatibilizer yields enhanced water resistance in spite of the strong intrinsic hydrophilicity of N6. In particular, two-step blending with reactive premixing is most effective in improving water resistance and reducing degradation of mechanical properties after moisture absorption.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760352302
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    A hybrid numerical technique to model 3-D flow fields in resin transfer molding processes (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1834-1851 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A hybrid two-/three-dimensional solution technique is presentedto model 3-D flow fields in resin transfer moeling using Darcy's low. The 3-D flow field is only solved for regions where all three velocity components are significant, thus largely reducing the number of unknowns. Elsewhere, the commonly used 2-D approximation for flow in thin gaps between plates is employe.d The method is applied to regions where the flow splits, such as T-joints. Because of the uncertainties associated with an accurate determination of the permeability in these regions, a simplified decompled procedure is procesed, which reduces the computational complexity. In this procedure, the flow front is advanced using the 2-D formulation. The 2-D formulation also provides the boundary conditions for the subsequent computation of the 3-D flow field without feedback of flow field information to the 2-d model. The governing equations are solved using boundary fitted coordinate systems (BFCS) together with the finite difference method (FDM). Numerical as well as algebraic grid generation and domain decomposition are employe dto generate grids that always concide with the continuously deforming and enlarging flow domain. Results that include the trackingof numerical tracer particles to visualize the three-dimensionality of the flow field are presented for isothermal flow of a Newtonian fluid through a T-joint. This detailed flow field description is expected to form the basis for a rather accurate simulation of quantitities that largely depend on the fluid particle pathlines, such as the degree of cure. The method is also extendable to shear-thinning fluids as well as to 3-D flow in the vicinity of the flow front.
    Additional Material: 22 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760352303
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    Theory of competition between breakup and coalescence of droplets in flowing polymer blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1872-1877 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The Smoluchowski equation for the breakup and coalescence of dispersed droplets has been solved for flowing polymer blends. A scaling form for the distribution of droplet sized derived and published for a system of clusters with fragmentation and coagualation was used in our dervation. Equations are developed here for the average droplet size and for the characteristic time of transition to steady state flow of blends with a high content of the dispersed phase. Expressions reasonably describing the average size of droplets for all concentrations were obtained by a theory modification. Measured dependences of droplet size on the blend composition can be matched only if simultaneous collisions of three and more droplets are considered. The results of the theory indicate that the mechanism of droplet breakup (formation of pieces with the same or different volumes) has only a small effect on their average size in concentrated systems. The dependence of droplet size on the shear rate in flow is determined by properties of the blend components, and is generally nonmonotonic.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760352306
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    Performance of reprocessed multilayer LDPE/nylon-6 film (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1878-1883 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Multilayer LDPE/nylon-6 films with an overall content of 71 wt% LDPE, 24 wt% nylon-6, and 5 wt% PE-based tie-layer adhesive were reprocessed under both minimal and extensive mixing conditions. Thermal and mechanical properties, oxygen and water vapor permeability, and morphology of the reprocessed samples were determined. The modulus and yield stress of the reprocessed films fell between those of the pure homopolymers, whereas percent elongation at break and energy-to-break for all reprocessed films were less than those of the homopolymers. In minimally reprocessed film, layering of LDPE (low-density polyethylene) and nylon-6 was retained, whereas in extensively mixed samples, nylon-6 domains were spherical and ranged from 0.2 to 7 μm. Minimally reprocessed film exhibited good O2 and H2O vapor barrier properties, whereas extensively-mixed samples had poor barrier properties. Properties of well-mixed blends prepared both with and without adhesive showed that 5 wt% adhesive did not compatibilize the LDPE and nylon-6 components.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760352307
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    Assessment of residual stresses during cure and cooling of epoxy resins (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1895-1898 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new stress monitoring technique, a stress-tracking device, is described here. It has been used to study some important properties of epoxy resin. Residual stresses, including a curing shrinkage stress and a cooling shrinkage stress, were measured automatically and continuously during curing and cooling. Simultaneously, information such as an apparent gelation time and glass transition temperature were obtained directly during the experiment. These epoxy resin properties were related to the extent of cure. Varying cure temperature produced changes of cure behavior, which resulted in different residual stresses.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760352309
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    Study of reaction injection molding of polyurethane microcellular foam (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1899-1906 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Processing of microcellular foam was investigated for the feasibility of production of tough and lightweight polyurethanes. To increase the nucleation rate in a gas-supersaturated resin, ultrasonic excitation was applied to the mixture of polyol(polyether-based polyol) and isocyanate(diphenyl methane diisocyanate). A microcellular structure was produced by two sequential steps, i.e., supersaturationof the polyol resin with nitrogen gas at elevated pressure and ultrasonic bubble nucleation right after the impingement mixing of two components of the polyurethane system. Theoretical analyses based on nucleation theories were employed to predict the rate of nucleation in the gas-supersaturated polyurethane. The rate of nucleatio in the resin was predicted by classical nucleation and cluster theories. In the experimental investigation, ultrasonic excitation was applied to increase the nucleation rate in the resin that had been saturated by nitrogen at a saturation pressure 〈 2.0 MPa.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760352310
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    Modeling the mechanical properties in polypropylene/polyamide-6 blends with core shell morphology (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1917-1922 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polypropylene/Polyamide-6 (PP.PA) blends containing maleic anhydride grafted elastomers were prepared by reactive blending. Three different types of core shell morphologies were obtained and characterized by transmission electron microscopy (TEM). The midulus of these elastomer midified PP/PA (70/30) blends with core shell type morphology is compared to predictions derived from the Kerner model. The multiphase morphology of these blends could be modeled by sequential application of the Kerner equation to two-phase subinclusions. Using morphological data ontained by TEM, good agreement between experimental and calculated values was ontained. The results are used to tailor PP/Pa-6 blends combining stiffness and toughness.
    Additional Material: 7 Ill.
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    Creep analysis of thermiplastics using stress relaxation data (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1931-1937 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: One of the major factors limiting the use of thermoplastics in engineeing applications is the inadequacy of existing design data. Much of the data do not span appropriate ranges of stress, strain, time, or temperature. This study addresses the need to develop an accelerated method for generating long-time design data to support the innovative use of engineering thermoplastics. In particular, stress relaxation tests (SRT) were performed on polycarbonate (PC) and midified poly(phenylene oxide)(PPO), and used to generate time-dependent design data through the short-time measurement of the material's current state without dependence on elastic modulus. The test results and analyses reported here indicate the SRT method to be an efficeint means of generating accurate and repeatable creep and secant modulus data which may be directly used in design. Therefore, SRT shows great potential both as a design parameter development tool, and as a quality control instrumetn for assessing batch-to-batch variability.
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    Characterization of microporous non-supported membrane top-layers using physisorption techniques (1995)
    Springer
    Journal of porous materials 1 (1995), S. 139-153 
    Details
    ISSN: 1573-4854
    Keywords: microporous ; sol-gel ; silica ; pore size ; adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Gas physisorption is a generally used technique for the characterization of porous solids. Microporous solids, however, need a different approach compared to mesoporous solids due to enhanced adsorption in pores of molecular dimensions. Therefore, conventional theories and models can not be used. The application of physisorption for microporous solids, and the interpretation of the isotherms is elucidated. Some models presented in literature for pore size assessment in the micropore range are discussed. Based on a number of criteria, the Horváth-Kawazoe model, modified for cylindrical pore geometry, is selected. N2 adsorption measurments on zeolites were performed to calibrate the method and to show the applicability and physical justification. Typical data obtained from experiments on non-supported microporous silica membrane top-layers show that the pore size distribution of these materials is bimodal, with a strong maximum at an effective diameter of 0.5 nm, and a weaker maximum at 0.75 nm.
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    URL: http://dx.doi.org/10.1007/BF00486653
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    Carbon-silica xerogel and aerogel composites (1995)
    Springer
    Journal of porous materials 1 (1995), S. 75-84 
    Details
    ISSN: 1573-4854
    Keywords: carbon ; silica ; xerogel ; aerogel ; composite ; adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract High surface area carbon-silica xerogels and aerogels were prepared by adding various amounts of activated carbon particles during gelation of tetramethyoxysilane (TMOS). Surface areas and pore structure of the gels were determined by nitrogen and water adsorption and desorption measurements. Carbon increased the surface area of silica gel and the carbon-silica gel composites were found to be hydrophobic. The pore structure of xerogel composites was dominated by carbon whereas that of aerogel composites was apparently controlled by silica component.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00486526
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    Probing the pore structure and dehumidifying characteristics of chemically modified zeolite Y (1995)
    Springer
    Journal of porous materials 1 (1995), S. 55-67 
    Details
    ISSN: 1573-4854
    Keywords: zeolite ; porous material ; adsorption ; desiccant ; natural gas ; dehumidification ; gas-fired cooling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This study was aimed at modifying the pore structure and surface chemistry of a zeolite to achieve an ideal material for gas-fired dehumidifying and cooling system application. Zeolite Y was chemically modified with various amounts of ethylenediaminetetraacetic acid (H4EDTA) corresponding to H4EDTA/Al (zeolite) molar ratio, X=0.5, 0.6, 0.75, 0.9 and 1.0 under reflux condition to achieve various degrees of dealumination. Sample treated with X=0.5 remained highly crystalline, but crystallinity of the samples decreased as the X increased. Although the sample treated with X=0.9 was x-ray amorphous, SEM micrographs indicated that the original crystal morphology was largely preserved. Chemical analysis and 29Si showed a progressive extraction of Al and Na with increased X. 27Al MASNMR indicated that AlIV was the only Al species up to X=0.75, whereas the x-ray amorphous phase (X=0.9) exhibited three peaks at 60, 52 and 38 ppm indicating the distortion of and change in AlIV coordination. Adsorption analyses using H2O, N2 or Ar as probe molecules indicated that the X-ray amorphous product remained essentially microporous having a broad micropore size distribution and a reduced hydrophilicity. Consequently, water adsorption isotherm changed from an extreme Type I to a moderate Type I. The moderate Type I isotherm with water is the key for its suitability as a desiccant in gas-fired dehumidifying and cooling system. These materials are also potentially useful in solar heating and cooling applications.
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    URL: http://dx.doi.org/10.1007/BF00486524
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    Molecular probe technique for the assessment of the carbon molecular sieve structure (1995)
    Springer
    Journal of porous materials 2 (1995), S. 19-23 
    Details
    ISSN: 1573-4854
    Keywords: carbon molecular sieve ; adsorption ; micropore size distribution ; molecular probe ; DR equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Nitrogen adsorption at 77 K is the most common technique for defining the surface area and pore volume of a porous material. However it is not adequate to assess the microporosity of carbon molecular sieves (CMS), because of activated diffusion effects. In this paper, a molecular probe technique was used to defining the pore size of CMS materials. Adsorption of gases (vapors) with different molecular sizes, were measured by a gravimetric method using a spring balance. The amount adsorbed at room temperature was recorded over a 24-h period. The following molecular probes were chosen: CO2 (0.33 nm), C2H6 (0.4 nm), n-C4H10 (0.43 nm), i-C5H112 (0.5 nm), and CCl4 (0.6 nm). The micropore volumes were estimated by the Dubinin-Raduhkevich (DR) equation. Assuming that the diameters of the micropores are larger than those of the adsorbed molecules, the micropore volume distribution of each sample was estimated. The results demonstrated that the main pore size of the studied CMSs are less than 0.5 nm. One of the samples had a narrow pore size distribution in the range of 0.33–0.43 nm, which is the critical pore size for kinetic separation of oxygen from nitrogen. It is concluded that the molecular probe technique is an effective mean to assess the CMS adsorbents structure, which is not currently possible using conventional approaches with a single adsorbate, such as nitrogen or argon.
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    Modeling physical adsorption on porous and nonporous solids using density functional theory (1995)
    Springer
    Journal of porous materials 2 (1995), S. 9-17 
    Details
    ISSN: 1573-4854
    Keywords: adsorption ; isotherm ; characterization ; modeling ; simulation ; pore size ; density functional theory ; argon ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The formalism of (nonlocal) density functional theory provides an attractive way to describe the physical adsorption process at the fluid-solid interface. It provides numerical results of analytic precision in a small fraction of the time required by a simulation technique. In particular, the ability to model adsorption in a pore space of slit-like or cylindrical geometry has led to useful methods for extracting pore size distribution information from experimental adsorption isotherms. However, critical comparisons of experimental isotherms with the isotherms predicted by density functional theory have shown important differences when using the usual prescription for the nonlocal free energy density functional. It is clear that these differences would affect the accuracy of such pore size information. We show in this paper how a small modification to the mean field computation of the intermolecular attractive potential results in excellent agreement with experiment for the systems studied.
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    Blockiness of olefin copolymers and possible microphase separation in the melt (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 18-27 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Solid-catalyzed copolymerization reactions of ethylene and α-olefins can produce complex mixtures generally regarded as “polyethylenes” (including linear low-density polyethylene). The selective nature of those catalysts can lead to block-like character in segments of polymer molecules, and these segments are sufficiently dissimilar (from a thermodynamic viewpoint) to allow for the possibility of microphase separation in the melt. Such a molecular-level phase separation would substantially alter the melt rheology, the crystallization process, and hence the mechanical and optical properties of the resulting product. It would, in principle, be identical to those occurring in conventional well-defined block copolymers, allowing the thermodynamic models developed for those systems to be extended to block-like polyolefins.
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    Influence of processing history on the properties of a thermotropic copolyester/polycarbonate blend (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 52-63 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Relationships between the rheological, morphological, and tensile properties of an immiscible blend of 25 wt% of a thermotropic liquid crystalline polymer (LCP) with polycarbonate are presented. The shear viscosity of the blend is intermediate between the two constituent materials, and indicates immiscibility in the melt. Extrudate swell behavior is examined and found to be closely related to that of polycarbonate. The morphology of the dispersed LCP phase varies between droplets and oriented fibrils, and is highly correlated with changes in tensile properties. Fibrils are associated with increased tensile modulus, and their development is favored in the elongation flow fields present in the spinline and in the die convergence section. In all cases, blend stiffness is less than that predicted for a continuous fiber-reinforced composite. Enhanced tensile modulus is associated with both extrusion from shorter length dies and increases in spinline draw ratio, with the latter proving the most important in fibril formation.
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    Masthead (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760350101
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    Preamble (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1-1 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760350102
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    History of commercial polymer alloys and blends (from a perspective of the patent literature)Based on: encyclopaedic dictionary of commercial polymer blends, L. A. Utracki, ed., ChemTech Pub., Toronto, Canada (1994). (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 2-17 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polymer blends are defined as mixtures of at least two polymeric species. Thus, the first patent polymer blend was a mixture of natural rubber, NR, with gutta percha patented by Alexander Parkes, an artist of Birmingham, in 1846. The first man-made polymer, nitrocellulose, NC was prepared by Braconnot in 1833. The resin was commercialized in 1868, but its first blends (with NR) were patented three years earlier. The first patent on blends of two synthetic polymers was granted in 1928 for poly(vinylchloride)/poly(vinylacetate), PVC/PVAc (latex blending). During the intervening 65 years, the polymer blend patent literature grew at an exponential rate; since 1983 the annual output has doubled, to exceed 3000 patents/year in 1993.
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    Instrumented impact evaluation of a toughened carbon fiber epoxy composite (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 129-136 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Instrumented impact testing and analysis were performed on an interlaminartoughened carbon fiber epoxy composite (Toray 3900-2/T800H) and a conventional (untoughened) epoxy composite (Fiberite 934/T300). Severity of impact was varied by using a wide range of impact energy. The effect of difference in the tup of the impact instrument was discussed. The residual compressive strengths after compact (CAI's) were measured by using a universal mechanical tester. The impact damage and delamination resistance of the toughened and conventional composites were quantitatively compared. At the same impact energy, the extent of damage was much less severe and the CAI was higher for the toughened composite. Relationships between the CAI's, the state of impact damage, and impact energy were investigated. Impact damage mechanisms for these two composites were not exactly the same. The impact damage of the conventional composite exhibited much greater extents of delamination. By contrast, interlaminar delamination in the toughened composite was found to be significantly suppressed, and the impact damage was more dominated by controlled matrix cracking/fiber damage, instead of catastrophic delamination. As a result, the CAI's of the toughened composite exhibited a monotonous decrease with increase in the impact energy and in the linear dimension of extents of damage.
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    Melting behavior and thermal properties of high density polythylene (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 151-156 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Thermal diffusivity of high density polyethylene (HDPE) was studied over a wide range of temperatures (25 to 200°C) by melting powdered HDPE in a cylindrical mold at several pressures (101.3 to 5065 KPa gage) and recording the temperature profiles at several radial positions. The energy equation was solved numerically for cylindrical geometry. The thermal diffusivity of HDPE was fit as a function of temperature, porosity, and pressure.
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    Re-examination of a proposed model for nonisothermal crystallization kinetics (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 170-172 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This communication is a theoretical re-examination of the model proposed by Choe and Lee for the nonisothermal crystallization kinetics of semicrystalline polymers.
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    Crosslinking in halogen containing novolac electron beam negative resists (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 180-183 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Halogenophenol novolac (HPN)-based negative resists exhibit excellent sensitivity and pattern resolution properties. The HPNs act as synergists for crosslinking with other irradiation labile compounds such as naphthoquinone diazide and bisazide vs. hydrogen halide (HX) elimination reaction, resulting in additional crosslinking, probably by aryl radical recombination and/or addition. We describe a new resist formulation based on HPN binder and melamine crosslinker (Cymel 303). In this case the irradiation induced HX elimination additionally catalyzes the melamine crosslinking.
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    Morphology and mechanical properties of virgin and recycled polyethylene/polyvinyl chloride blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 64-71 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In this study, blends of virgin and recycled polyethylene (PE) and poly(vinyl chloride) (PVC), with a methylmethacrylate-ethylacrylate copolymer as a processing aid, were prepared in the molten state. Different additives such as ethylenevinylacetate copolymers, ethylene-methacrylic acid ionomer, and two peroxides (dibenzoyl and dicumyl), in the presence of a coupling agent, were used to compatibilize the blend or possibly induce graft structures. The blends' morphologies, tensile properties, and impact properties were studied. For blends with low copolymer concentration (below 3 wt%) the mechanical test data indicated a good performance. In the case of blends with ethylene methacrylic acid ionomer, improvements in the mechanical properties were obtained also at higher additive concentrations. Of the two peroxides, better results were obtained using the dibenzoyl one. The morphological studies indicated that the blends that showed good mechanical properties were better dispersed and had improved interphase adhesion.
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    Performance blends based on recycled polymers (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 72-78 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The recent growth in the post-consumer recycling of plastics presents an opportunity for developing new, value-added blend products from the recycled polymers. However, in order to develop blends with useful performance characteristics, suitable techniques of compatibilization and impact modification must be employed. In this study, reactive toughening and compatibilization techniques have been found to be particularly useful in achieving high thermal embrittlement resistance in the blends of recycled poly(ethylene terephthalate) containing functionalized ethylene copolymers and polycarbonate. Reactive compatibilization of recycled polyolefin blends with poly(ethylene terephthalate) and polyamide has also been investigated.
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    Masthead (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760350201
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    Development of polymer blend morphology during compounding in a twin-screw extruder. Part IV: A new computational model with coalescence (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 115-127 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In Part II of this series of publications, the first generation model of morphology evolution during polymer blending in a twin-screw extruder was presented. The model was based on a simplified flow analysis, and an assumption that dispersion occurs via drop fibrillation followed by disintegration. In the present Part IV, several modifications of the model are discussed. (i) The flow analysis was refined by computing the pressure profiles. (ii) The flow paths and strain history of the dispersed droplets within the screw elements are computed directly, which makes it possible to determine the drop susceptibility to deformation and break. (iii) Besides the fibrillation mechanism, a drop-splitting mechanism for low supercritical capillary numbers is incorporated. (iv) The choice of breakup mechanism is based on micro-rheological criteria. (v) The coalescence effects are taken into account. (vi) The theoretical model is self-consistent, without adjustable parameters. The validity of theoretical assumptions was evaluated by comparing the model predictions with the experimental droplet diameters at different positions in the twin-screw extruder.
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    Water sorption in a novel liquid crystalline epoxy resin (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 137-143 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Water sorption tests have been carried out for a novel epoxy resin having liquid crystalline character. The sorption isotherm. Relative to the expoxy resin cured in the nematic phase, does not indicate any substantial difference from the resin cured in the isotropic state. This is an indication that, as far as this class of thermosets is considered, the liquid crystalline order does not affect mechanism and equilibrium values of water uptake.
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    Microwave processing of two-phase systems: Composites and plymer blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 144-150 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The objective of the current paper was to extend the relationships between complex polymer structures and microwave absorptivity that were formulated in the first three papers of this series (1-3). The microwave processing of composite and polymeric blends via a cylindrical resonance wave cavity and a rectangular standing wave applicator is described. These polymeric materials were irradiated in a low power (〈 100W) electric field at 2.45 GHz. Graphite-epoxy laminates were processed in both standing and traveling wave applicators. Rapid heating and curing were achieved in both cases. An observation of significance was that, with proper tuning of the traveling wave device (the precursor of a protable repair tool), it proved to be highly effective in processing. Additionally, a compatible blend of poly(methyl methacrylate) and poly(vinylidene fluoride) was heated in and applicator and the rates of temperature rise were demonstrated to depend upon morphology.
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    Stress-strain behavior and dynamic mechanical properties of poly(1,1-dimethyl-1-sila-cis-pent-3-ene), poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene) and of these polymers after crosslinking with sulfur (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 157-164 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Mechanical properties of polymers can be described by their stress/strain curves and by their behavior under dynamic mechanical thermal analysis (DMTA). The purpose of this paper is to report such mechanical properties for two unsaturated polycarbosilanes: poly(1, 1-dimethyl-1-sila-cis-pent-3-ene) (I) and poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene) (II). Tensile strength, elongation at break, modulus, bending modulus, Tg, and tan δ for I, II and for sulfur crosslinked I and II have been measured. The influence of polymer molecular weight, quantity of crosslinking agent, cure time, presence of carbon black filler, the effect of crosshead speed, and frequency on these properties was investigated.
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    The effects of physical aging on the brittle fracture behavior of polymers (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 165-169 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effects of physical aging on the failure behavior of a typical brittle polymer, polystyrene, have been studied. Properties examined were creep rupture lifetimes, fatigue lifetimes, and environmental stress cracking in ethanol. Fractured samples were examined both optically and by scanning electron microscopy to determine the degree of crazing. It was found that a longer physical aging time produced shorter lifetimes in all cases. The main reason for this is the reduction in craze strength caused by a reduced toughness due to physical aging. A long aging time was found to delay craze formation, but once formed, these crazes were much less stable than those formed with a short aging time. The effects of aging are important on failure prediction criteria and on testing methodologies, and the implications are discussed.
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    Investigation of cure in epoxy acrylate resins using rheological and dielectric measurements (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 184-189 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dielectric and rheological measurements are reported for the cure in a series of mixtures of an epoxy-acrylate with n-butyl methacrylate. The level of the initiator and properties of the epoxy acrylate and n-butyl methacrylate influence the cure characteristics and morphology of the film formed. Analysis of the rheological data indicates that during the curing process, microphase separation occurs within the mixture. The changes in the dielectric relaxation behavior with composition of the completely cured material is also consistent with microphase separation occurring in these resins while they are cured.
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    Monomer chain cross-transfer constants and cross termination factor evaluations on styrene-acrylonitrile copolymerization (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 195-201 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Using low conversion bulk copolymerization experimental data and the apparent rate constant model, the monomer chain cross-transfer rate constants and the cross-termination coefficient were evaluated. It was found that the dependence of the cross-termination coefficient on composition is a function of initiator efficiency and that monomer chain cross-transfer rate constant are relevant for the theoretical estimation of the molecular weights and molecular weight distributions.
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    Rheology of thermoplastic starch: Effects of temperature, moisture content, and additives on melt viscosity (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 202-210 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The melt viscosity of thermoplastic starch has been investigated as a function of temperature, moisture content, and processing conditions. The effects of various low molecular weight additives have also been studied. Starch melts exhibit power law behavior over the range of shear rates studied. Melt viscosity decreased with increasing temperature and moisture content (MC). The power law index m increased with increasing temperature. The consistency K decreased with increasing temperature and increasing moisture content. Moisture content during the pelletizing step influenced melt viscosities measured after equilibration to different MCs. All additives studied except glycerol monostearate (GMS) significantly lowered the melt viscosity of starch, some more effectively than water relative to starch with 15% MC. Starch with GMS had viscosities essentially the same as, or slightly higher than, starch/water. This behavior may be due to the presence of unmelted helical inclusion complexes of starch and GMS. Starch formulations at 160°C exhibited melt visocosities similar to an LDPE of melt index 1.8.
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    Review of stabilization of polyolefin insulated conductors. Part II: Characteristics of good stabilizers and methods of evaluation (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 218-221 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In a previous paper, the theory of polylefin stabilization and the major factors contributing to degradation were discussed. This paper reviews the methods of test employed to date, the characteristics of a good stabilization system, and the experimental work we propose to use to study the problem. The characteristics of a stabilizer which are reviewed are: color, melt temperature, solubility, resistance to extraction, migration, phase state, structural arrangement, energy considerations, and thermodynamic potential. The methods of test reviewed include: pedestal testing, oven aging, oxygen uptake, testing under stress, melt flow testing, thermal analysis by DSC, thermal analysis by TGA, color change, torque rheometry, and aged elongation. Our approach will be to quantify the effects of antioxidant, metal deactivator, and blowing agent on stability by doing differential scanning calorimetry (DSC); to study fracture surfaces with scanning electron microscopy (SEM) to study diffusion rate of the stabilizer and reaction rate of the degradation process; and to use dynamic mechanical analysis (DMA) to measure the change in loss modulus with aging.
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    Comparison of microwave and thermal cure of an epoxy/amine matrix (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 233-239 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An investigation was carried out into the effect ofa microwave cure on an epoxy prepolymer with a cycloaliphatic diamine mixture, as compared to a standard thermal cure. The microwave waveguide and process (propagation mode TE01) were adjusted to obtain large homogeneous samples. The extent of reaction, x, was measured during the microwave processing by size exclusion chromatography and differential scanning calorimetry. A good estimate of x was found using a modified DiBenedetto equation correlating x and the glass transition temperature Tg. The homogeneity of the samples was checked during the last steps of cure, showing the efficiency of the microwave processing and waveguide. The influence of the nature of the mold (metallic or dielectric) on the reaction kinetic was also investigated. Samples cured by both thermal and microwave processing were characterized by dynamic and static mechanical properties and then compared with those of fully crosslinked networks, i.e., postcured at a high temperature.
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    Effects of inserts on the injection molding process (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 247-251 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Injection molds often contain blocks of dissimilar material for improved cooling; they may also contain blocks of movable metal as a means of ejecting large parts from the mold. In this case, the blocks of metal are made of the same material, but the resistance at the interface between them has a marked influence on the cooling in the local area near the interface. In many other cases, inserts may be required because of wear in a particular mold section, or because efficient mold design is needed to produce similar parts. Hence, any mathematical model for analysis of heat transfer in injection molds must be general enough to apply to interfaces with and without gaps (i.e., with and without resistance to the flow of heat at the interface) for similar, as well as dissimilar, materials. A new and accurate model for prediction of heat transfer in heterogeneous (zoned) molds is presented in this paper. Through the solution of real problems with this model, the effects of differing material properties and interfacial thermal resistance are studied and the results are reported. It is observed that inserts have both local and global effects on the injection molding process; the overall ejection time for a part may be shortened, and the surface appearance of a part may be improved by correct placement of inserts.
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    A simple approach to determining three-dimensional screw characteristics in the metering zone of extrusion processes using a total shape factor (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 274-283 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: It is of great importance in designing extruders to predict the screw characteristics, that is, the throughput in terms of the screw speed and the pressure gradient along the down-channel direction. The screw characteristics depend on the extruder geometry, the operating conditions, and material properties of non-Newtonian fluids. This paper suggests a simple approach to determining the screw characteristics for a three-dimensional flow in a channel with a finite aspect ratio (ratio of a width to a depth, W/H) by introducing a Total Shape Factor (Ft) to correct a two-dimensional flow analysis for a channel with an infinite aspect ratio. In the present study, the Total Shape Factor (Ft) was defined as a ratio of a net flow rate obtained by the three-dimensional analysis to that by the two-dimensional analysis. In the proposed approach, the quantity, ∂Ft/∂(H/W), which turns out to be almost constant, offers important information for understanding the effects of the flights. Threfore, ∂Ft/∂(H/W) is extensively reported in this paper in terms of several dimensionless parameters. This simple approach with such a database will be very useful for extruder designers to predict screw characteristics.
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    Masthead (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760350401
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    Modeling the dielectric response of unsaturated polyester resin during cure (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 284-288 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The dielectric relaxation of unsaturated polyester resin during cure was modeled using a modified Williams-Watts decay function. The dielectric response was studied using dielectric measurements coupled with two dynamic mechanical measurement methods. It was found that the variation of the relaxation time during cure is a WLF process using Tg (α) (α-conversion) as the varied temperature. It was shown that this process fits the Williams-Watts decay function Φ(t)=exp(-(t/τ)β) where τ-relaxation time and β-empirical parameter are time dependent. It was found that τ obeys a time dependent power law rule and β depends linearly on log(time). Using this modified decay function, it was shown that the experimental dielectric response measured during cure agrees well with the computed response. Relaxation times above and below the dielectric measurement system capability were computed thus, demonstrating the capability of yielding the entire relaxation times spectrum during cure, out of a single limited frequency dielectric measurement.
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    Cold-drawing (necking) behavior of polycarbonate as a double glass transition (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 304-309 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The thermomechanical behavior of poly(bisphenol A carbonate) (PC) undergoing cold-drawing (necking) over a large range of temperature and strain rate has been studied. The cold-drawing of PC has been described from a material particle perspective in terms of true stress and strain relationships. The isothermal draw stress is shown to be a material parameter, and the true stress-strain behavior of necked material above the true drawing stress follows conventional treatment by rubber elasticity. Cold-drawing is described as a double glass transition: first, a transition from an isotropic glass to an isotropic rubber at the yield point, then, on unloading after stretching of a rubbery mesophase, a transition from an oriented rubber to an oriented glass.
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    A state variable model for high strength polymers (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 310-316 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Displacement controlled experiments on nylon 66, poly(etherether ketone), and poly(ether imide) at room temperature suggest that nonlinear elastcity is not a good model for these polymers. Rather, qualitative evidence is presented that a state variable model shows promise. In this model, the rate of deformation is the sum of the elastic and the inelastic rates of deformation. The elastic rate of deformation is given by an objective formulation of Hooke's law, and the inelastic deformation is an increasing function of the overstress, the difference between the Cauchy stress and the equilibrium stress. The equilibrium stress is a state variable, and represents the stress that can be sustained at rest following deformation. Load controlled tests, intended to verify or falsify the model, show that the creep rate at the same stress level can be different on loading and unloading, and that the creep rate need not increase with an increase in creep stress level. These anomalous results can easily be explained by the introduction of the overstress concept, and by proper evolution of the equilibrium stress. They confirm the usefulness of the overstress concept for the modeling of these polymers.
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    A constitutive model for the nonlinear viscoelastic viscoplastic behavior of glassy polymers (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 331-344 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Two features of the glassy state of an amorphous polymer, which play a key role in determining its mechanical properties, are the distributed nature of the microstructural state and the thermally activated (temporal) evolution of this state. In this work, we have sought to capture these features in a mechanistically motivated constitutive model by considering a distribution in the activation energy barrier to deformation in a thermally activated model of the deformation process. We thus model what is traditionally termed the nonlinear viscoelastic behavior as an elastic-inelastic transition, where the energetically distributed nature of inelastic events and their evolution with straining is taken into account. The thermoreversible nature of inelastic deformation is modeled by invoking the notion of strain energy stored by localized inelastic shear transformations. The model results are compared to experimental data for constant true strain rate uniaxial compression tests (nonmonotonic) at different rates and temperatures; its predictive capabilities are further tested by comparison with compressive creep tests at different stress levels and temperatures.
    Additional Material: 19 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760350407
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    Solidification of thermoviscoelastic melts. Part I: Formulation of model problem (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 351-364 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The solidification of a molten layer of amorphous thermoplastic between cooled parallel plates is used to model the mechanics of part shrinkage and warpage and the buildup of residual stresses in the injection molding process. Flow effects are neglected, and a thermorheologically simple thermoviscoelastic material model is assumed. The equilibrium thermomechanical properties of the material and the shift function can be temperature- and pressure-dependent. The model allows material to be added to fill the space created by the packing pressure applied during solidification; therefore, this model can be used to assess packing-pressure effects in injection molding. The model also accounts for freeze-off effects in which the cavity pressure is controlled by the solidification process and must therefore be determined as a part of the solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760350409
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    Solidification of thermoviscoelastic melts. Part II: Effects of processing conditions on shrinkage and residual stresses (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 365-383 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The solidification of a molten layer of thermoplastic between cooled parallel plates is used to model the mechanics of part shrinkage and the buildup of residual stresses in the injection-molding process. Flow effects are neglected, and a thermorheologically simple thermoviscoelastic material model is assumed. The model allows material to be added to fill the space created by the pressure applied during solidification, so that this model can be used to assess packing-pressure effects in injection molding. Parametric results are presented on the effects of the mold and melt temperatures, the part thickness, and the packing pressure - the pressure applied during solidification to counteract the effects of volumetric shrinkage of the thermoplastic - on the in-plane and through-thickness shrinkages, and on residual stresses in plaque-like geometries. The packing pressure is shown to have a significant effect on part shrinkage, but a smaller effect on residual stresses. Packing pressure applied later in the solidification cycle has a larger effect. Mold and melt temperatures are shown to have a much smaller effect. The processing parameters appear to affect the through-thickness shrinkage more than the in-plane shrinkage. While the results are presented in terms of normalized variables based on the properties of bisphenol-A polycarbonate, they can be interpreted for other amorphous thermoplastics such as modified polyphenylene oxide, polyetherimide, and acrylonitrile-butadiene-styrene.
    Additional Material: 35 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760350410
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    Effect of NOx environments and stress on degradation of mechanical properties of Kevlar 49 and nylon 6 (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 411-418 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Mechanical and chemical mechanisms may act synergistically to degrade the mechanical properties of polymers. This synergism should be considered during design of components for sustained loads in hostile environments. If these polymers are to be used as load-bearing structural elements in automobile and industrial environments, they are likely to be simultaneously exposed to such environments and stress. These studies explore the deleterious effects of gaseous pollutants (e.g. NOx in air) and mechanical stress on polymers. This research included studies on nylon-6 and composites of nylon-6 yarns embedded in a bis-A-phenolic resin with an amine curing agent, as well as single fibers and yarns of poly(p-phenylene terephthalamide) (DuPont Kevlar 49) as bare fibers and also embedded in an epoxy matrix. The protective effect of embedding fibers in the epoxy matrix was demonstrated. NOx concentrations were varied between 0 and 1.5%. The sustained loads during exposure were in the range of 50 to 80 percent of the ultimate stress short term load carrying capability of the fibers. Exposure times varied from several minutes to months. Electron spin resonance spectroscopy (ESR) is used in these studies to explore the kinetics of bond rupture and how they relate to the environmental and stress loading histories in nylon. Kevlar 49 degradation studies were conducted by measuring times required for sample failure in NOx concentrations at various stress levels. Preliminary studies on the single fibers indicate a stress-NOx synergism over the range of stresses (48 and 77% of ultimate) and 0.1 and 1.5% gas concentrations. Yarn samples exhibited this synergism over a wide range of stresses (40 to 80% of ultimate). Bare yarn degradation was accelerated by NOx concentrations in air as low as 0.1%. We view these effects as having practical technological significance since these lower NOx concentrations approach the level of emissions from exhaust from older model automobiles.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760350506
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    Molecular weight dependence of the fracture toughness of glassy polymers arising from crack propagation through a craze (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 419-425 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We investigate criteria for craze failure at a crack tip and the dependence of craze failure on the molecular weight of the polymer. Our micromechanics model is based on the presence of cross-tie fibrils in the craze microstructure. These cross-tie fibrils give the craze some small lateral load bearing capacity so that they can transfer stress between the main fibrils. This load transfer mechanism allows the normal stress on the fibrils directly ahead of the crack tip in the center of the craze to reach the breaking stress of the polymer chains. We solve for stress field near the crack trip and use it to relate craze failure to the external loading and microstructural quantities such as the craze widening (drawing) stress, the fibril spacing, the molecular weight, and the force to break a single polymer chain. The relationship between energy flow to the crack tip due to external loading and the work of local fracture by fibril breakdown is also obtained. Our analysis shows that the normal stress acting on the fibrils at the crack tip increases linearly as the square root of the craze thickness, assuming that the normal stress distribution is uniform and is equal to the drawing stress acting on the craze-bulk interface. The critical crack opening displacement, and hence the fracture toghness is shown to be proportional to [1-(Me/qMn)]2, where Me is the entanglement molecular weight, Mn is the number average molecular weight of polymer before crazing, and q is the fraction of entangled strands that do not undergo chain scission in forming the craze.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760350507
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    Enhanced polycarbonate toughness. I: Measurement methodology (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 471-476 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The JIC values for core-shell-particle-toughened polycarbonate were determined at different temperatures and at 0, 2.5, 5.0, 7.5, and 10.0 phr particle content by six similar methods, using compact tensile specimens. At the 2.5 phr toughener level, the JIC values ranged from 2878 to 6100 J/m2, and at 7.5 phr, they ranged from 6125 to 10,760 J/m2, dependent only upon how the same JI-Δ a data were interpreted. This indicates that more work will be required before a reliable method of JIC measurement that can be applied to tough polymers is achieved.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760350603
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    Kinetics modeling and time-temperature-transformation diagram of microwave and thermal cure of epoxy resins (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 461-470 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Stoichimetric mixtures of a diglycidyl ether of bisphenol A (DGEBA)/ diaminodiphenyl sulfone (DDS) and a DGEBA/meta phenylene diamine (mPDA) were cured using both microwave and thermal energy. Fourier transform infrared (FTIR) was used for the measurement of the extent of cure and thermal mechanical analysis (TMA) was used for the determination of the glass transition temperature (Tg). The cure kinetics of the DGEBA/mPDA and DGEBA/DDS systems were described by an autocatalytic kinetic model up to vitrification in both the microwave and thermal cure. For the DGEBA/mPDA system, the reaction rate constants of the primary amine-epoxy reaction are equal to those of the secondary amine-epoxy reaction, and the etherification reaction is negligible for both microwave and thermal cure. For the DGEBA/DDS system, the reaction rate constants of the primary amine-epoxy reaction are greater than those of the secondary amine-epoxy reaction and the etherification reaction is only negligible at low cure temperatures for both microwave and thermal cure. Microwave radiation decreases the reaction rate constant ratio of the secondary amine-epoxy reaction to the primary amine-epxy reaction and the ratio of the etherification reaction to the primary amine-epoxy reaction. Tg data were fitted to the DiBenedetto model. A master curve and a time-temperature-transformation (TTT) diagram were constructed. The vitrification time is shorter in microwave cure than in thermal cure, especially at higher isothermal cure temperatures. For the DGEBA/mPDA system, the minimum vitrification time is two to five times shorter in the microwave cure than in the thermal cure. For the DGEBA/DDS system, the minimum vitrification time is 44 times shorter in the microwave cure than in the thermal cure.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760350602
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    Morphology and mechanical properties of liquid crystalline copolyester and polyester elastomer blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 528-537 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Blends of a polyester elastomer (PEL) having a hard segment of polyester (PBT) and soft segment of polyether (PTMG) and a liquid crystalline copolyester (LCP), poly(benzoate-naphthoate), were prepared in a twin-screw extruder. Specimens for mechanical testing were prepared by injection molding. The morphology of the LCP/PEL blends was characterized under different processing conditions. To determine what conditions were necessary for the development of a fibrillar morphology of LCP, we have studied the effect of processing method (extrusion and injection molding), injection molding temperature (below and above the melting point of LCP), and gate position in the mold (direct gate and side gate). SEM studies revealed that some extensional flow was required for the fibrillar formation of LCP and the fibrillar structure of LCP was controlled by the processing method. The morphology of the blends was found to be affected by their compositions and processing conditions. SEM studies revealed that finely dispersed spherical domains of LCP were formed in the PEL matrix and the inclusions were deformed in fibrils from the spherical droplets with increasing LCP content and injection temperature. The mechanical properties of the LCP/PEL blends were also found to be affected by their compositions and processing conditions. The mechanical properties of LCP/PEL blends were very similar to those of polymeric composite. An attempt was made to correlate the structure of the blends from the scanning electron microscope with the measured mechanical properties. All of the aspects of the morphology were possible to explain in terms of the mechanical properties of the blends. A DSC study revealed that the crystallization of PEL was accelerated by the addition of LCP in the matrix and a partial compatibility between LCP and PEL was predicted. The rheological behavior of the LCP/PEL blends was found to be very different from that of the parent polymers, and significant viscosity reductions were observed in the blend consisting of only 5 wt% of LCP.
    Additional Material: 17 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760350611
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    Masthead (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760350701
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    Rubber modified epoxy resin. III: Reaction injection molding process (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 564-576 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Reaction injection molding of amine terminated butadiene acrylonitrile copolymer (ATBN) modified epoxy resin was investigated through computer simulation and experiment. The epoxy system composed of diglycidyl ether of bisphenol A (DGEBA) and triethylene tetramine (TETA) was employed since this system indicated a relatively high reaction rate. The coupled balance equations of momentum, chemical species, and energy within the disc-type mold cavity were solved using finite difference techniques. The predicted temperature and conversion profiles within the mold were compared to experimental results. The domain correlation length data calculated from the simulation model were compared with the results of SEM micrographs. A moldability analysis was performed to find the optimum molding conditions. The moldability window decreased as the mold thickness was increased.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760350703
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    The copolymerization of methacrylates in a counter-rotating twin-screw extruder (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 587-597 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The copolymerization of n-butylmethacrylate with 2-hydroxypropylmethacrylate was studied in a closely intermeshing counterrotating twin-screw extruder. The average molecular weight of the product can be increased by increasing the screw rotation rate or the die resistance or by decreasing the throughput or the barrel temperature. The conversion can be improved by decreasing the throughput, increasing the die resistance, and (within limits) increasing the barrel temperature, as well as through post-initiation. Compared with various classical polymerization processes, this situation requires that particular attention be paid to the occurrence of a gel effect, the existence of a thermodynamic ceiling temperature, and the reactivity ratio of the monomers used.
    Additional Material: 18 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760350705
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    Masthead (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760350801
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    Numerical simulation of fiber orientation in injection molding of short-fiber-reinforced thermoplastics (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 604-618 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The present study develops a numerical simulation program to predict the transient behavior of fiber orientations together with a mold filling simulation for short-fiber-reinforced thermoplastics in arbitrary three-dimensional injection mold cavities. The Dinh-Armstrong model including an additional stress due to the existence of fibers is incorporated into the Hele-Shaw equation to result in a new pressure equation governing the filling process. The mold filling simulation is performed by solving the new pressure equation and energy equation via a finite element/finite difference method as well as evolution equations for the second-order orientation tensor via the fourth-order Runge-Kutta method. The fiber orientation tensor is determined at every layer of each element across the thickness of molded parts with appropriate tensor transformations for arbitrary three-dimensional cavity space.
    Additional Material: 19 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760350707
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    Chemically oxidized polypyrrole: Influence of the experimental conditions on its electrical conductivity and morphology (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 642-647 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of synthesis conditions on the electrical conductivity and the morphology of a chemically oxidized polypyrrole was investigated. It was found that the electrical conductivity of polypyrrole was strongly dependent on the pyrrole/FeCl3 ratio, which controls the redox potential of the reaction medium. The reaction temperature and the reaction duration also influence the electrical conductivity of the polypyrrole. A considerable influence of the nature of the solvent used on the aggregation state of polypyrrole particles was demonstrated. Optimal experimental conditions are proposed.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760350803
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    In situ composite: Phenolphthalein polyethersulfone - thermotropic liquid crystalline polymer blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 658-665 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Phase behavior, thermal, rheological and mechanical properties plus morphology have been studied for a binary polymer blend. The blend is phenolphthalein polyethersulfone (PES-C) with a thermotropic liquid crystalline polymer (LCP), a condensation copolymer of p-hydroxybenzoic acid with ethylene terephthalate (PHB-PET). It was found that these two polymers from optically isotropic and homogeneous blends by means of a solvent casting method. The homogeneous blends undergo phase separation during heat treatment. However, melt mixed PES-C/PHB-PET blends were heterogeneous based upon DSC and DMA analysis and SEM examination. Addition of LCP in PES-C resulted in a marked reduction of melt viscosity and thus improved processability. Compared to pure PES-C, the charpy impact strength of the blend containing 2.5% LCP increased 2.5 times. Synergistic effects were also observed for the mechanical properties of blends containing 〈 10% LCP. Particulates, ribbons, and fibrils were found to be the typical morphological units of PHB-PET in the PES-C matrix, which depended upon the concentration of LCP and the processing conditions.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760350805
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    Time dependent response of polycarbonate and microcellular polycarbonate (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 673-679 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Microcellular polycarbonate is a novel cellular material with cells on the order of 10 μm in diameter and a cell density on the order of 109 cells per cm3. In this study the room temperature creep response of microcellular polycarbonate is experimentally determined and compared with the creep behavior of polycarbonate. The viscoelastic response of polycarbonate and microcellular polycarbonate is characterized using Schapery's theory of nonlinear viscoelasticity. Polycarbonate exhibited a nonlinear creep response at stress levels above 24.13 MPa, while the nonlinear behavior in microcellular polycarbonate was initiated at lower stress levels. Creep strains of microcellular polycarbonate contain a significantly higher viscoplastic component compared with the unfoamed material.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760350807
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    Diffusion of butanediol in poly(butylene terephthalate) (PBT) melt and analysis of pbt polymerization reactor with surface renewal (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 703-708 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A reactor with surface renewal, originally designed for poly(ethylene terephthalate) (PET) polymerization, was applied for poly(butylene terephthalate) (PBT) polymerization. A comprehensive model including side reactions was developed and compared with the experimental results. The diffusivity of butanediol (BD) in PBT melt was measured separately by desorption experiments (Db - 1.08 × 106 exp(-32600 / RT) (m2/min)). Optimum operating temperature for PBT polymerization was found to be around 250°C in order to avoid degradation.
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    URL: http://dx.doi.org/10.1002/pen.760350810
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    Diffusion of low molecular weight substances into a laminar film. I: Rigorous solution of the diffusion equation in a composite film of multiple layers (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 709-721 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A rigorous solution of the diffusion of penetrant into a laminar film comprised of multilayers of m components is presented by an orthogonal-expansion method. As the simplest practical cases of m - 2 and m - 3, with stepwise distribution of both diffusion coefficients and solubility coefficients at the boundary between respective layers, the diffusion properties in the transient state are analyzed in detail. That is, changes in the penetrant concentration distribution within the laminar film and the total amount of penetrant sorbed within the film both with time after exposing the film to an atmosphere of fixed penetrant concentration are calculated for A-B as well as A-B-A type layer arrangements. The calculation is performed while keeping (L2/L1) at a constant value of 2.0 but varying the diffusion coefficient ratio of (D1/D2) from 102 to 10-2, and/or varying the solubility coefficient ratio of (S1/S2) from 1 to 10, where L1 and (L2 - L1) are the thickness D1 and D2 are the diffusion coefficients of penetrant, and S1 and S2 are the solubility coefficients in the A-component and B-component, respectively. The sorption curves deviate considerably from those of Fickian curves of homogeneous film with (D1/D2) - 1 in their respective ways. The results obtained here can be applied to the diffusion in a single component polymer film having a surface layer with different diffusion properties from that of the inner side of the film caused by differing distributions in molecular orientation or degrees of crystallinity.
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    URL: http://dx.doi.org/10.1002/pen.760350811
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    Finite element analysis modeling of powder injection molding filling process including yield stress and slip phenomena (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 741-753 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: For a science-based design of the Powder Injection Molding (PIM) process, it would be desirable for designers to have a numerical analysis tool capable of predicting the PIM filling process as a design aid. In this regard, the present study is aimed at developing a numerical analysis system to simulate the PIM filling process based on a new physical modeling taking into account rheological characteristics of powder/binder mixtures, namely the yield stress and the apparent slip phenomena. In particular, two different slip models were employed to represent the apparent slip phenomena. In accordance with the new physical modeling, the numerical simulation of the PIM filling process was accomplished by combining a finite element method and a finite difference method. It was found that the slip layer plays a role of not only a lubricating layer but also a thermal insulation layer. In this aspect, the slip layer model seems to represent the apparent slip phenemena better than the slip velocity model with regard to both the momentum and the thermal transport phenomena. The present paper presents the physical modeling, numerical scheme, and some numerical analysis results showing the effect of the yield stress and slip phenomena.
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    URL: http://dx.doi.org/10.1002/pen.760350903
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    Electronic Resource
    Extrusion die design for multiple stripes (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 759-767 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Two numerical approaches have been applied to examine the possibility of adding shims to conventional extrusion dies such as T-dies and coat-hanger dies to produce multiple stripes. The first numerical approach is based on a one or two-dimensional lubrication approximation and the second one is the three-dimensional finite element simulation. Both approaches are applicable, but the lubrication approximation is accurate and much simpler to use. The extruded stripes are assumed to obey a non-Newtonian power-law model. It has been found that the T-die with a shim can produce multiple stripes of acceptable uniformity, irrespective of the strip numbers and widths and the power-law index. The coat-hanger die with a shim did not deliver multiple stripes with good uniformity. Adding an outer manifold to the coat-hanger die can serve as an effective means to reduce flow nonuniformities.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760350905
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