ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Articles  (1,561)
  • Chemical Engineering  (1,289)
  • Industrial Chemistry and Chemical Engineering  (272)
  • Wiley-Blackwell  (1,561)
  • Annual Reviews
  • 2005-2009
  • 1990-1994  (1,561)
  • 1994  (790)
  • 1993  (771)
  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 393-399 
    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 univariant element, Q1 P0, and the multivariant elements, Q1+P0 and R2+ P0, are compared for the numerical simulation of the flow in extrusion dies. The pressure distribution obtained by using the Q1 P0 element was found to be afflicted with the checkerboard pressure mode. On the other hand, the multivariant elements, Q1+ P0 and R2+ P0, gave accurate and physically reasonable velocity and pressure distributions. The computed values of the pressure drop across extrusion dies matched well with the pressure drop determined experimentally.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 377-382 
    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 viscoelastic responses of some molten polymers, and particularly of low density polyethylene (LDPE), are known to vary with processing history. Reasons for the variations include the effects of shear history on morphological states of the polymer, or on its molecular weight parameters. A typical low density polyethylene has been used to test the shear-history dependence concept following a variety of processing steps. The polymer was sheared in single-screw and twin-screw extruders, and in a high speed melter / mixer (Gelimat). Samples also were precipitated from very dilute solutions in trichlorobenzene and in p-xylene. GPC analyses showed that, in general, these procedures did not affect the various moments of molecular weight. An exception was the Gelimat-mixed sample, for which mild reductions in Mn and Mw were noted. In contrast, melt viscosity and elasticity readings, the former from low shear evaluations and the latter from extrudate swelling, were affected by the various procedures. A drop in melt viscosity and in elasticity was observed, being most pronounced for precipitated and twin-screw extruded versions of the LDPE. Reductions also were observed in the specimen sheared in the Gelimat instrument. Following conditioning at the test extrusion temperature (170°C), viscous and elastic responses tended to revert to those of the unsheared control sample, the exception again being the sample sheared in the Gelimat melter / mixer. Of the various mechanisms proposed in the literature to account for transient property changes such as those reported, temporary changes in the degree of chain entanglement appear the most satisfactory explanation. Irreversible alterations in viscoelastic properties may be associated with changes in molecular weights due to processing at high shear.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 400-409 
    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 model for the filling stage of injection molding of viscoelastic thermoplastics in cavities of complex shape is presented. The model considers two-dimensional melt flow, with converging and diverging flow patterns induced by complex boundary shape and by the presence of an obstacle. The model is non-isothermal (with the melt loosing heat to the mold walls as it travels into the cavity) and handles a viscoelastic (following the White-Metzner model) material with properties that vary with temperature, shear rate, and pressure. The numerical method is based on finite differences, with boundary fitted curvilinear coordinates used in the mapping of the flow field (which has an arbitrary shape that evolves with time) into a time invariant rectangle. The numerical results reveal geometry-induced asymmetries in the flow and thermal fields as well as the effect of various process parameters on the pressure and temperature profiles in the cavity. The model admits variable cavity thickness, thus allowing for a treatment of the cavity thickness as a process parameter in the simulations.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 497-500 
    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 use of polymeric materials in building or construction applications is steadily increasing. Therefore, the potential for these materials to be exposed to fire is also increased. The understanding of the pyrolysis characteristics of these materials is thus a necessity. There are many standard tests used to evaluate materials. Unfortunately, the correlation between these tests and large scale fire is less than desirable. A new bench scale rate of heat release apparatus, the Cone Calorimeter, is now being used more frequently in pyrolysis testing of polymeric materials. This apparatus has been shown to correlate much better between room scale testing and large scale fire testing. The cone Calorimeter provides a pyrolysis profile of a material under ambient oxygen conditions. Characteristics such as ignition time, total heat release, maximum rate of heat release, mass loss during pyrolysis, CO2, CO, and smoke production are determined. In this work several almost neat polymers are examined and the general pyrolysis characteristics of these polymers are discussed. The objective of this work is to provide information of basic polymeric pyrolysis properties of these materials. Variations in the material, i.e., molecular weight, polydispersity, and residual catalysis, along with changes in testing procedures, can have dramatic effects on results. Obviously the addition of flame retardant and flame retardant packages to any of these materials will have dramatic effects on results.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993) 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 513-521 
    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 overall isothermal crystallization kinetics for nucleated and non-nucleated isotactic polypropylene (iPP)-dotriacontane systems was investigated. Adipic acid was used as the nucleating agent. Half-time was determined via differential scanning calorimetry as a function of the experimentally controlled variables dilution, crystallization temperature, and the addition of nucleating agent. The influence of these variables on crystallization mechanism and spherulitic structure, as implied by the Avrami analysis, was determined. The influence of these variables on fold surface energy was examined by the Lauritzen and Hoffman analysis.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    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 overall non-isothermal crystallization kinetics for nucleated and non-nucleated isotactic polypropylene (iPP) in dotriacontane systems was investigated. Adipic acid was used as the nucleating agent. Crystallization peak temperature was determined via differential scanning calorimetry as a function of the experimentally controlled variables iPP concentration, cooling rate, and nucleating agent concentration. The influence of these variables on crystallization mechanism and spherulitic structure as implied by the Ozawa and Ziabicki analyses was determined. The non-isothermal crystallization kinetics presented here are the first for iPP-diluent systems with and without nucleating agent.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 543-548 
    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 static shear strength and static friction of three thermoplastics have been investigated for the case of contact between a bulk plastic sample and a very smooth metallic plate. The minimum tangential force required to shear the interfacial adhesion bonds between the two surfaces was measured and defined as the adhesion component of friction Fa. Experimental results showed that Fa is large when the surface energy is high or the interfacial energy is small and that a correlation may exist between this force and the work of adhesion evaluated from Dupré equation. The real area of contact Ar was also measured using an optical device designed to handle samples and experimental conditions similar to the static friction tests. It was found that Ar is proportional to Pa0.9 where Pa is the apparent pressure of contact and an increase of Fa with Pr was observed. The static shear strength τ has been evaluated as the ratio Fa/Ar, and its relationships with the real contact pressure P approximated by linear functions. It was concluded that τ increases at high P, although it has not been verified for ultra-high-molecular-weight polyethylene. An attempt has been made to explain the observed break in the data. The results indicated that (τ/τb) = κ′(τa/Pa) where b refers to bulk, a to apparent values, and κ′ is a proportionality constant that depends on the plastic material.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 549-558 
    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 variety of different styrene monomers [styrene (S), p-fluorostyrene (p-FS), pentafluorostyrene (PFS), p-chlorostyrene (p-ClS), p-bromostyrene (p-BrS), p-methylstyrene (p-MS), p-tert-butylstyrene (p-tBS), p-methoxystyrene (p-MOS), p-ethoxystyrene (p-EOS), and p-propoxystyrene (p-POS)] have been polymerized by radical and cationic mechanisms. Copolymers of S/PFS, S/p-ClS, S/2-vinyl-naphthalene (2-VN), and S/p-phenylstyrene (p-PhS) were prepared by radical polymerization. All polymers were fully amorphous and transparent and exhibited only one glass transition temperature in the temperature range 77 to 141°C. Thin films of the polymers were subjected to external electrical partial discharges (PD). Typically, 20 PD experiments were conducted for each polymer and the data for the time to breakdown were adapted to the two-parameter Weibull distribution function. The resistance towards PD of the various polymers was found to depend strongly on the monomeric structure. Complementary PD experiments on a series of narrow molecular mass polystyrenes confirmed that the minor variation in molecular mass between the different styrene polymers is of no importance for the PD resistance. The PD resistance of the homopolymers decreased in the following order: PS ≍ P(p-MS) 〉 P(p-tBS) ≍ P(p-BrS) 〉 P(p-POS) 〉 P(p-ClS) ≍ P(p-MOS) 〉 P(p-EOS) ≍ P(p-FS) 〉 P(PFS). The time to breakdown for copolymers of S and PFS decreased monotonously with increasing PFS content. Styrene copolymers with low molar contents of 2- VN and p-PhS exhibited a higher resistance towards PD than PS. The results are discussed with reference to various properties of the studied polymers, such as segmental mobility, ionization potential, resonance stabilization, and reactivity of the radicals formed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993) 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 11
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 614-621 
    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 glass transition temperatures in bismaleimide-based resins were investigated using different stoichiometric ratios of 1, 1′-(methylenedi-4, 1-phenylene)bismaleimide (BMI) and 4, 4′-methylenedianiline (MDA). The resin cure involves a low temperature primary amine addition to the maleimide double bonds and a high temperature homopolymerization of the maleimide double bonds. The network topology and the glass transition temperature changes with resin composition and curing conditions were determined using differential scanning calorimetry (DSC). An empirical model was used to relate the glass transition temperature to the extents of the amine addition and the homopolymerization reactions in 1:1 and 2:1 BMI:MDA resins. The changes in thermal properties with resin post-cure were also examined.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 12
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 640-644 
    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: Dynamic mechanical properties, tensile properties, and scanning electron microscopy of blends of poly(methyl methacrylate) and polycarbonate were investigated after phase separation above their cloud point temperature by annealing in a hot press. The dynamic mechanical properties show that phase separation proceeds more distinctly for the blends annealed at higher temperature and for longer time. The scanning electron micrographs show that the morphology of phase separated blends varies with the conditions of heat treatment. The tensile properties of phase separated blends deteriorate on account of the coarsening of the brittle dispersed phase over the optimum size and the occurrence of voiding during the heat treatment.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 13
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 665-674 
    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 packing stage starts at the end of mold filling. During this stage, additional material is forced into the mold to compensate for the shrinkage during subse-quent cooling. Underpacking results in molded parts with dimensional variation. Overpacking causes flash at the parting lines, stick during ejection, and excess residual stresses resulting in warpage. The packing stage is thus extremely important in the determination of the final quality of the product. Despite its importance, analysis of the packing stage has been relatively ignored, particularly the viscoelastic effect. In this work, the analysis of the isothermal packing stage is presented for a Maxwell fluid. A set of governing equations is derived for a two-dimensional mold and solved using the Galerkin finite element method. In addition to the distribution of velocity and pressure, the model predicts the stresses in the planar direction, which could be used for subsequent calculation of the residual stresses.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 14
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 675-685 
    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 this work was to determine the effects of selected polyester catalysts on the reaction of a polyester with epoxy functional polymers. Polyesters containing various catalyst metals were melt blended with either an ethylene-co-glycidyl methacrylate or a styrene-co-glycidyl methacrylate copolymer. The viscosities of the blends were monitored as a function of mixing time using torque rheometry. In addition, the molecular weight distributions of selected samples were analyzed using gel permeation chromatography. Both the torque rheometry and the gel permeation chromatography results indicate that the polyester reacts with epoxy functional polymers. This reaction occurs under conditions and at processing times which are readily obtainable in conventional melt processing equipment. Furthermore, the reaction kinetics of polyesters with glycidyl methacrylate copolymers are dramatically affected by the nature of the catalyst system used to prepare the polyester. Under the conditions used, antimony catalysts are particularly effective at promoting the reaction between polyesters and the epoxy functionality and the activity of the catalysts studied appears to decrease in the following order: antimony 〉 gallium 〉 tin ≃ titanium 〉 germanium. Manipulation of the polyester catalyst system may offer a method to control the extent of reaction obtained in reactive processing of polyesters with epoxy functional compounds.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 15
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 709-715 
    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 flow kinematics of power-law fluids in fishtail dies is studied. A general isothermal three-dimensional finite element code developed by the authors is used for the flow analysis purpose. The basic geometry of the fishtail die is defined by simple super-elliptical curves, which allows a smooth transition from a circle to a slit. The three-dimensional path line and the residence time distribution (RTD) are calculated from the velocity field obtained from the finite element solution of the conservation equations. The effects of the rheological properties and the die geometry on the path line pattern and the residence time distribution are investigated. The results indicate that as both the length of the transition zone and the fishtail angle increases, the residence time distribution becomes more uniform. However, the power-law index does not affect the residence time distribution significantly.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 16
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 736-741 
    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 polymers of the aromatic nitrogen compounds N-methyl-pyrrole (P-N-Me-PPY), carbazole (PCarb), and aniline (PANI) have been investigated with electro-optical and surface analytical methods. The in-situ reflection spectra indicate the formation of polarons or bipolarons during electrochemical oxidation, depending on polymer type. The absorption bands can be attributed to changes in the electronic structure with regard to the applied potential. Photocurrent spectra of P-N-Me-PPY and PCarb show a p-type semiconducting behaviour for the polymers in the reduced state. The transition to the oxidized state with quasi-metallic properties is indicated by a significant shift in the Fermi level energy and can be followed with XPS and UPS measurements.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 17
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 838-844 
    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: Extruded films of liquid crystalline polymer (LCP)/fluoropolymer blends were melt drawn to develop uniaxial orientation of a microfibrillar dispersed LCP phase. The anisotropy of the films increased with increasing draw and LCP content in the blend. Laminated composite plates were prepared using the extruded sheets as prepreg. The mechanical properties and coefficient of thermal expansion (CTE) of the prepreg and laminates agreed well with predictions from composite lamination theories. The potential for replacing glass fiber reinforced fluoropolymers with LCP/fluoropolymer blends in applications such as microwave circuit boards is discussed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 18
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993) 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 19
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 865-876 
    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 review presents a general picture of suspension, dispersion, and interfacial polycondensation processes employed for the preparation of beaded resins, dry powders, and high solid dispersions. The polymer systems covered include polyamides, polyesters, polycarbonates, polyurethanes, and phenol-formaldehyde and urea-formaldehyde resins. Basic features of heterogeneous polycondensation processes are outlined, and different mechanisms of particle formation in suspension, dispersion, and interfacial polycondensation are discussed. Effects of manufacturing parameters such as feed ratio, droplet/particle stabilizer, and stirrer speed on product characteristics are also briefly covered.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 20
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 781-788 
    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 extrudate swell and the dynamic rheological properties of poly(butylene terephthalate) (PBT) and polyamide 6 (PA6) binary blends were investigated at 240°C. The extrudate swell of the blend varies with the viscosity ratio and composition of constituents, and it is several times larger than that of homopolymers when the viscosity ratio of constituents is around unity. The dynamic oscillatory data could be interpreted by Oldroyd's emulsion model proposed by Graebling, et al. These results suggest that the extrudate swell is caused by the shape recovery of the dispersed particles. A semi-empirical method to estimate the terminal relaxation time with experimental data was introduced, and a clear correlation between the extrudate swell and the terminal relaxation time was obtained.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 21
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 819-826 
    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: Much work in recent years had focused on the improvements of the impact properties of engineering thermoplastics by the addition of a low modulus modifier that contains polar moieties as a result of polymerization or that has been modified to contain polar moieties as a result of various grafting techniques. Styrenic block copolymers (styrene-ethylene/butylene-styrene) functionalized with maleic anhydride have proved useful as impact modifiers and compatibilizers in blends with engineering thermoplastics. This paper focuses on the use of these functionalized elastomers to modify nylon 6. In such compositions, a nylon material with unique mechanical performance may be achieved using the functionalized elastomer either alone or in combination with an unfunctionalized styrenic block copolymer. The optimization of performance in these rubber toughened polyamide blends using various types of styrenic block copolymers is discussed. The morphology as it pertains to performance is also reviewed. The information contained herein may prove useful in obtaining a better understanding of the mechanisms of compatibilization and modification of nylon 6 systems.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 22
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 827-837 
    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: Oriented blends of poly(ethylene terephthalate) (PET) and high density polyethylene (HDPE) with and without compatibilizing agent have been studied with regard to orientation temperature, stretch rate, extension ratio, mode of orientation, and blend composition. These oriented blends have been characterized using infrared spectroscopy and differential scanning calorimetry. The tensile and tensile impact properties were also investigated. The results show that blends with compatibilizer show strain hardening upon orientation, whereas the blend without compatibilizer does not strain harden upon orientation. The blends with less PET content have been difficult to orient. The morphology of these blends show fibril structure, highly oriented in the direction of stretch. Infrared measurements show that PET within the blend has undergone strain induced crystallization upon orientation. It has also been observed that the mechanical properties, such as the modulus and ultimate stress, show improvement upon orientation. Simultaneously stretched blends show better physical properties than sequentially oriented blends.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 23
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 895-900 
    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 paper illustrates the factors that control brittle failure under fatigue loading for test specimens cut from medium-density polyethylene pipes for gas distribution. A square bar specimen cut from a pipe with a notch was made and a fatigue test was conducted to cause a brittle failure. To obtain the correlation among stress range, frequency, temperature, and cycles to failure in this fatigue test, Coffin-Manson's frequency-modified fatigue life equation was adopted and the material constants were determined. By gradually lowering the frequency, the resistance to creep can be estimated because cycles to failure - indicating the fatigue damage - decreased, and the actual loading time - indicating the creep damage - increased.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 24
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 923-930 
    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 interfacial tension, phase morphology, and phase growth was determined for four polymer blend systems: polyethylene/polystyrene, polyethylene/polyamide-6, polystyrene/polyamide-6, and polystyrene/poly(ethylene terephthalate). Generally, high interfacial tension correlates with coarse phase morphology and rapid phase coalescence. The addition of various potential compatibilizing agents to these binary blend systems results in lowered interfacial tension, finer and stabilized phase morphologies. The characteristics of different compatibilizing agents were compared for several of the blend systems. We also look at the influences of compatibilizing agents on mechanical properties of the blend systems. Some compatibilizing agents are able to produce substantial improvements in ultimate properties.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 25
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 937-943 
    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: Unidirectional sheets were extruded of an in-situ composite of thermotropic liquid crystalline Vectra B950 in a matrix of polyphenylene-ether and polystyrene. Three important processing parameters were systematically varied: draw-ratio, slit opening and extruder throughput. Morphology and mechanical properties of these films were determined, and qualitatively related to the processing conditions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 26
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 959-970 
    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 to accurately measure or predict the Residence Time Distribution (RTD) in designing extruders and/or in setting up a proper operating condition, because chemical reactions depend significantly on the RTD and temperature when chemical reactions take place during the extrusion process. A previous method to predict the RTD can analytically determine RTD, Residence Time Distribution Function f(t) and Cumulative Residence Time Distribution Function F(t), based on a simplified two-dimensional velocity field in an extruder. However, this previous method cannot accurately take into account the three-dimensional circulatory flow inside the extruder. The present paper suggests a new method to accurately determine the RTD taking into account the three-dimensional circulatory flow and presents a new formula derived to calculate f(t). In order to demonstrate the applicability of the new method including the circulatory flow effect, RTD, f(t) and F(t) were calculated based on a three-dimensional velocity field obtained via a quasi-three-dimensional finite element analysis. It was found that the previous method has a tendency to underestimate the RTD, owing to the neglect of the three-dimensional circulatory flow in comparison with the new method.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 27
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 980-988 
    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: Experimental data confirm the utility of the following simple equation in predicting the spin coating behavior of polyimide precursor solutions: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm h} = {\rm c\beta }_{\rm 0} {\rm k}^{{\rm \beta }_{\rm 1} } {\rm \omega }^{{\rm \beta }_{\rm 2} } {\rm t}^{{\rm \beta }_{\rm 3} } \quad\quad\quad\quad{\rm (1)} $$\end{document} in which \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {c = {\rm polymer\, solution\, solid\, weight\, fraction;}} \\ {\beta _i = {\rm fitted\, coefficient\, (Greek\, letter\, beta)};} \\ \quad{h = {\rm film\, thickness\, after\, cure\, or\, solvent\, removal};} \\ \quad{k = {\rm polymer\, solution\, kinematic\, viscosity, centistokes};} \\ {t = {\rm time},{\rm and;}} \\ \quad{\omega = {\rm wafer\, spin\, speed, rpm (Greek\, letter\, omega)}.} \\ \end{array} $$\end{document}.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 28
    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: Ternary systems consisting of polypropylene (PP), ethylene-propylene-dieneterpolymer (EPDM) and different types of inorganic fillers (kaolin, BaSO4) have been investigated with respect to their mechanical behavior. On the basis of an Interphase model, it was possible using the modified van der Poel equation to describe the temperature dependence of the storage modulus G′(T) and the loss modulus G″(T). The interphase properties G′(T) and G″(T) could be calculated.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 29
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1251-1260 
    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: Signal deterioration of optical discs depends strongly on the substrate surface roughness. Characteristics of surface roughness of the molded substrate have been studied in order to clarify the transcription mechanism of smooth surfaces in injection molding of polycarbonate resin. When the melt temperature, mold temperature, and injecting rate are low, microscopic flow marks more than 5 nm deep are observed on the surface. These flow marks are formed when the melted resin near the mold wall is cooled to the no-flow temperature of resin before it comes into contact with the mold wall. Molding transcription improves by optimizing the molding conditions for preventing these flow marks. As a result, the surface roughness of the molded substrate obtained is 3.2 nm in maximum height Rmax, which is nearly equal to that of the mold stamper at 2.7 nm in Rmax.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 30
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1279-1287 
    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 finite element numerical analysis of preform inflation associated with the injection blow molding process has been developed using a neo-Hookean constitutive model. The analysis is capable of predicting final wall thickness distributions for axisymmetric mold geometries. Experimental studies were conducted on a Uniloy injection blow molding machine (Model 189-3 and Model 122). A twelve ounce (355 mL) cylindrical bottle mold was instrumented with contact sensors, thermocouples, and pressure transducers. Visualization studies of the inflation process were performed using specialized tooling and high-speed video cameras. The experimental studies provide justification for analyzing the deformation by means of a static elastic approach. The predicted wall thickness distribution is in reasonable agreement with the experimental data. Nonuniformities in the temperature distribution in the preform were found to have the most significant impact on the inflation behavior and the resulting wall thickness.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 31
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1301-1307 
    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 α-relaxation of a bisphenol-A type epoxide oligomer has been investigated in the vicinity of the glass transition temperature (Tg) by the direct current (DC) transient method. The logarithm of the DC transient current for the oligomer was well approximated by the third order function of the logarithm of time. The complex dielectric constant was calculated through the Fourier transformation of that approximation function according to Simpson's integration rule in a frequency range of 10-5 - 1 Hz. At the temperature around the Tg (45°C), the dielectric α-relaxation process of the oligomer was found to be governed by the Havriliak-Negami equation. The relationship between the DC conductivity (σ) and the dielectric relaxation time (τ), σ·τm = const, is valid near and above the Tg of the oligomer. The DC transient current method combined with the DC conduction and the dielectric bridge measurements is considered to be a practical tool for analyzing the dielectric α-relaxation process of the epoxide oligomer over a wide frequency and temperature range.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 32
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1329-1335 
    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, styrene-(ethylene-co-butylene)-styrene (SEBS) triblock copolymer (Kraton G-1652) was modified with maleic anhydride (MA). The maleated SEBS was used as compatibilizer for the blends of Nylon 6 (PA6) and SEBS. The morphology and impact strength of the blends were measured as functions of concentration and MA graft ratio of maleated SEBS. The compatibility and fracture mechanism of the blends were evaluated from the SEM micrographs of the xylene-etched surfaces and of fractured surfaces. Some of the blends exhibited an impact strength up to about 30 fold greater than neat PA6. The fracture involved both both cavitation and shear yielding. The mechanism of compatibilization of maleated SEBS in the ternary components blends was proposed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 33
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1341-1351 
    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 paper reports on the theoretical and experimental studies of structure formation and strengthening (stiffening) of flexible-chain polymers. Two techniques of strengthening relying on the melt extrusion, i.e., orientational crystallization (crystallization initiated by melt extension) and drawing (uniaxial stretching of a crystallized polymer) are analysed by theory. The experiments involved preparation and study of melt extruded films and film fibers of linear polyethylene formed by the two techniques mentioned above. The effect of the degree of orientation and other parameters of the formation processes on the mechanical characteristics and the factors limiting the ultimate values of these characteristics are discussed. It is shown that multistage drawing succeeds in achieving a higher tensile strength and elastic modulus (1.2 and 35 GPa, respectively) than the orientational crystallization, which gives 0.8 and 15 GPa. The strengthening by drawing is accompanied by microcrack formation. In contrast, no discontinuities are observed in orientationally crystallized samples up to their ultimate extension.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 34
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1370-1371 
    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
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 35
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1381-1389 
    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: Because of the inability of existing automotive bumpers to absorb energy during impacts over the supports, energy absorbers have to be used to make bumpers effective in barrier impacts. A parametric analysis of a novel double-beam bumper concept has shown that its performance, in terms of energy absorption and impact forces, is insensitive to the location of the point of impact. Physical realizations of this concept, which may not require more material than existing designs, and which are particularly suited to thermoplastic materials, have been developed.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 36
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1270-1278 
    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: Flow in a three-dimensional channel with a sinusoidally-wavy, vertical wall is examined for the case of applied down- and cross-channel velocity components. An important parameter for the analysis of the nature of laminar mixing in the flow field occurs when the changes in the downstream direction can be decoupled from the changes in the cross-channel direction, thereby allowing for a two-dimensional solution of the system of equations. This paper shows the effect on the nature of laminar mixing when the decoupling of the momentum equations from a fully three-dimensional case to one where a two-dimensional solution can be performed. Experiments are performed on a channel with sinusoidally varying vertical walls that cover the range of decoupling criteria. Silicone pigmented either white or black was run in the apparatus, cured, and cross-sectioned. The cross sections embody a local, detailed history of the state of mixing as it proceeds down the mixer. The amount of mixing is presented as a function of position at each cross section for the different channel configurations. The nature of mixing changes from a linear growth rate in the amount of interfacial area to an exponential rate as the amplitude of the wave is increased. Results demonstrate the existence of chaos, islands, and the factors affecting the mixing behavior.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 37
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 6-11 
    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 class of materials based on a spirodilactam structure has been recently synthesized as part of research into new polymeric materials. Not only is the spirodilactam structure novel, but it was not even the intended product in the synthesis as originally designed. The polymerization process discovered by the reaction of 4-ketopimelic acid or its corresponding spirodilactone with primary amines opened a new field of polysprodilactam chemistry. This paper describes the chemistry leading to the discovery of spirodilactam-based polymers and initial applications in the area of thermoplastics and thermosets. Most recent developments to be covered include aromatic spirodilactams and isomeric spirodilactams.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 38
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 12-16 
    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: Spirodilactam bisallylether is a new high temperature performance monomer. It melts at 154°C, and is thermally inactive in forming a homopolymer. However, it reacts readily with a bismaleimide via “ene” reaction. Therefore, it could be used as a comonomer and an effective toughening modifier for bismaleimide. The properties of the blends of spirodilactam bisallylether and 4,4'-bismaleimidodiphenyl-methane were studied. The cocured resins have high glass transition temperature, 〉 300°C. By adding 30 to 40 mole % of the bisallylether, the compact tension toughness of the bismaleimide was improved to 0.7 MPa-m1/2. Therefore, the resins have a combination of high glass transition temperature and toughness. They also showed good flexural properties. Despite the high water absorption, 5 to 7%, the resins retained high hot/wet flexural properties because of the high glass transition.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 39
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 59-68 
    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: Four immiscible blend systems, styrene-maleic anhydride/styrene-acrylonitrile (SMA/SAN). styrene-maleic anhydride/acrylonitrile-butadiene-styrene (SMA/ABS), poly(vinylidene fluoride)/SAN (PVF2/SAN), and PVF2/ABS, were investigated. The effect of adding up to about 10 wt% of a third polymer that is miscible with each blend component, poly(methylmethacrylate) (PMMA), was determined. In every case, the addition of PMMA led to the improvement of properties such as tensile strength, tensile elongation, and notched impact strength. Furthermore, the addition of PMMA resulted in finer, more uniform dispersions of the primary blend components. The experimental results are interpreted in terms of interfacial activity of the common phase component, PMMA.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 40
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 81-85 
    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: Differential scanning calorimetry (DSC) was used to investigate the solid-state cure process of poly(phenylene sulfide)(PPS) resin. Virgin PPS resin in an open sample pan was cured in DSC cell. Either air or oxygen was used as a curing atmosphere. Cure temperatures were in the range of 200 and 250 °C, which are below the melting point of PPS resin. Cure temperature as well as atmospheric condition influenced the cure behavior of PPS in the solid state. Both the rate and the amount of cure increased with increasing cure temperature. On the other hand, the time to reach the maximum cure rate was independent of cure temperature. Changing the atmosphere from air to oxygen increased both the cure rate and the amount of cure. The size effect of PPS particles on the cure reaction was also discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 41
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 109-115 
    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: Slow crack growth was measured in the perpendicular and parallel directions relative to the extrusion direction of the pipe. For five pipes from different manufacturers, the anisotropy factor, the lifetime to fracture in the perpendicular direction divided by lifetime in the parallel direction, varied from 1.2 to 4.7 for complete fracture and 1.4 to 4.0 for crack initiation. The degree of molecular orientation was determined by measuring the shrinkage that occured when a pipe specimen was heated near its melting point. The amount of shrinkage correlated with the anisotropy factor for slow crack growth. The shape change after shrinkage was related to the flow pattern of the resin during extrusion and the cooling rate after extrusion.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 42
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 135-140 
    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 complex Young's modulus, E*(ω), and the complex strain-optical coefficient, O*(ω), of poly(ether sulfone) (PES), polysulfone (PSF), and polyethermide (PEI), were measured over the frequency range 1 to 130 Hz. The data were analyzed with a modified stress-optical rule: The Young's modulus was decomposed into two complex functions, EG*(ω) and ER*(ω); the modified stress-optical coefficient, CR and CG, associated with the rubber (R) and glass (G) components, respectively, were determined. The results for six polymers, including polystyrene, poly(α-methyl styrene), and bisphenol A polycarbonate were compared with each other. One of the coefficients, CR, equivalent to the stress-optical coefficient in melts, mainly depended on the way in which phenyl groups were connected to the chain. The other, CG, was in the range of 20 to 40 Brewsters, and did not strongly depend on the details of polymer structure. The component function, EG*(ω), which was located in the glassy region and originated from the high glassy modulus, was almost the same in shape when plotted against ω with double logarithmic scales. The R component, ER*(ω), located at the long time end of the glass-to-rubber transition zone, was slightly sensitive to the molecular structure of polymers.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 43
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 159-165 
    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: While there is abundant evidence that the molecular weight distribution (MWD) of a linear polymer has an influence on the shape of the viscosity function, the ability to convert the viscosity function to an MWD has been questioned. Using strictly numerical techniques, we have shown that the viscosity function can be transformed to the MWD, but always with some distortion. However, distinct bimodality can be qualitatively preserved through both the MWD-viscosity and viscocity-MWD transforms.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 44
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 169-173 
    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 microcellular plastics, an unfoamed skin that is integral with the foamed core can be created by allowing the nucleating gas to diffuse from the surfaces of a gas saturated specimen prior to foaming. In this paper, a semi-empirical model is proposed that predicts the skin thickness variation in microcellular foams as a function of gas desorption time. The model shows good agreement with experimental results on the polycarbonate-carbon dioxide system.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 45
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 174-189 
    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 paper proposes “Deformation Characteristics” (DC) as a new deformation measure of screw extrusion processes, based on the Green deformation tensor. In contrast to previous strain measures heuristically proposed by Mohr, et al., Mckelvey, and Pinto and Tadmor, the new DC can naturally incorporate the demixing phenomena and systematically take into account the three-dimensional circulatory flow with the screw flight effect. Therefore, DC can be regarded as an improved strain measure. “Weighted Average Deformation characteristics” (WADC) is also proposed to indicate the overall deformation characteristics as a quantitative measure to the “goodness of mixing” of the extrusion process. The present paper includes discussion on delicate differences between DC and several other strain measures in case of the two-dimensional velocity approximation, and on the application of DC into a general three-dimensional velocity field obtained by a quasi-three-dimensional finite element analysis of extrusion processes. In determining WADC in the three-dimensional application, the residence time distribution function, including the three-dimensional circulatory flow effect, is used.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 46
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 229-237 
    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: Non-isothermal flow is simulated in the screw and kneading disc elements in a modular co-rotating twin screw extruder. Methods of calculating mean temperature rises for individual elements are discussed and results are presented. The implications of non-isothermal operation for scale-up is discussed. A method is then described for making calculations in a modular co-rotating machine, that contains many different elements. Example calculations are given showing the tendency of larger machines to buildup greater temperatures when viscous heating is included.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 47
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 221-228 
    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 study of the influence of a compatibilizing agent on phase morphology development in a 75/25 polyethylene/polyamide-6 blend in a modular co-rotating twin screw extruder is presented. The development of phase morphology along the axis of the modular screw was observed by cooling the extruder and removing the polymer from the screw channels. Changes in phase morphology due to the addition of a compatibilizer have been investigated using scanning electron microscopy. Sufficient quantities of compatibilizing agent produce significant increases in the rate of mixing and also reduce the scale of the phase morphology. Much larger quantities (5%) than actually required for interface coverage are needed for rapid mixing. This seems to be due to the high viscosity of the matrix.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 48
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 251-251 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 49
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 50
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 260-265 
    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: Penrose states that quantum effects can occur even in relatively large systems when energy differences remain small. This is just the situation with polymer materials. A quantum description by Penrose of the formation of quasi-crystals can be rewritten to apply to polymer crystallization. The implications of the need to take account of quantum effects are discussed. Another approach based on the quantization of energy levels in clusters of atoms offers a possible explanation of heat setting in nylon and polyester fibers. Finally some problems of the interpretation of quantum theory are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 51
    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 novel approach to a truly dynamic thermodynamics is proposed in which equilibrium is defined in terms of explicit time, distance, and acceptable error scales. This approach involves reformulating the second law of thermodynamics in terms of an excess energy that vanishes at equilibrium instead of an entropy that assumes some unknown maximum value. Excess energy is defined mathematically as the total Legendre transform of energy with respect to an independent set of extensive variables. Excess energy is effectively the free energy functional of a nonequilibrium system and is a function of the time, distance, and acceptable error scales. Elimination of entropy from thermodynamics requires recognizing temperature as a thermal stress, proportional to the antimetric component of the stress tensor that is neglected when one assumes the validity of Cauchy's second law of motion. The inclusion of temperature as part of the stress-strain couple completes the science of thermomechanics and opens the way for a practical unification of chemistry and physics in strictly mechanical terms.The last sentence of the abstract shows how high the goals that Lindem meyer set for himself were. I personally do not agree with the idea that mechanics is the queen of all sciences, and that given deep enough probing one could achieve “a practical unification of chemistxy and physics in strictly mechanical terms”; for instance, electromagnetism has full citizenship's rights in physics, and it is hard to conceive that it could be reduced to mechanics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 52
    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 interfacial strength of two paper-polypropylene-paper laminates used for electrical power transmission cable insulation has been measured using a peel test after a variety of conditionings that simulate the service thermal stress conditions. Immersion in dielectric oil at 23°C causes little decrease in peel strength, but heating in the oil at 90°C causes a rapid initial loss followed by a slow loss of strength. Cyclic and static heating show that cyclic fatigue is not a factor as the initial loss of strength occurs in a time comparable to the first two test cycles and further heating causes much less loss of strength. Tensile and compressive stresses resulting from cable winding have no effect on the loss of bond strength during heating in oil. Vacuum drying of the laminate and oil (as in cable manufacture) before heating results in less decrease in peel strength than heating without prior drying. Optical and electron microscopy show minimal wetting of the paper fibrils by the polypropylene with only a few having been either normal to or at a steep angle to the polypropylene surface. That is, the fibrils appear to be parallel to the interface and only partially immersed in the polypropylene. Micrographs show little, if any, differences between the interfaces on the two sides as well as little paper on the polypropylene after delamination and vice versa. It is suggested that the bonding mechanism is a combination of weak mechanical interlocking and secondary bonds. It is also suggested that swelling of the polypropylene relative to the paper by the dielectric oil at 90°C weakens the interfacial bond.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 53
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 290-300 
    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: Variations of stress with temperature for stretched networks of trans-polyisoprene networks in the crystallization region are reported. Such profiles are characteristically U-shaped with the stress at lower temperatures often climbing to high levels. Valley widths of the profiles narrow as annealing temperature increases to about 50°C, then widen at yet higher temperatures. The degree of crystallization at 22°C is 37% and independent of deformation and annealing temperature. The β crystal form is overwhelmingly present with traces of other crystal forms appearing only at high deformations. The theory of stress-induced crystallization provides a good description of experimental results provided the nucleation parameter σ is dependent upon deformation. Therefore, the data provide good qualitative support for the theory in its current form.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 54
    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: Polyalkylenebenzoxazoles of high molecular weight (inherent viscosity values from 0.76 to 2.95) were prepared from 4,6-diaminoresorcinol dihydrochloride and aliphatic diacids in polyphosphoric acid by heating at 180 to 200°C for 3-5 h. Melting points of the polymers ranged from 148 to 423°C, depending on the length of the alkylene chain. Glass transition temperatures were relatively low, ranging from 50 to 100°C and did not show the pronounced odd/even effect noted for melting points. In all cases, rapid weight loss occurred above 400°C. No evidence for the formation of a molecular composite was observed in an attempt to prepare in situ a rod-like polybenzoxazole in a polyalkylenebenzoxazole.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 55
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 56
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 93-101 
    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: Low levels of oligomer molecules are generally desirable in polymeric materials. It is known that several reactor variables can affect the oligomer distribution, and therefore it is useful to have predictive models for molecular weight distribution. The normal approach of a differential equation-based model is very complex to set up if it is applied rigorously to include all the non-Flory aspects of the step growth polycondensation and in particular the interfacial polycarbonate polymerization. In this paper, simple methods based on the Monte Carlo method and Stockmayer distribution are applied to simulate the effects of mass-transfer, unequal reactivity, and the starting stoichiometry of the polycondensing functional groups on the oligomer distribution. It is shown that these parameters can have a significant effect on the oligomer weight distribution and polydispersity of the final polymer.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 57
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 308-317 
    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 true crystallite modulus of polyoxymethylene (POM) was evaluated experimentally and thoeretically as a function of temperature. The mechanical deformation mechanism of POM was lattice-dynamically predicted and confirmed by measuring the stress-induced vibrational frequency shifts of the infrared and Raman spectra, which were interpreted on the basis of anharmonic potential field.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 58
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 141-152 
    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 ultra-high strength/modulus, extended chain polyethylene fiber (Spectra® fiber) composite has shown great potential as a lightweight armor material with its extraordinary capability of absorbing the kinetic energy of projectiles. But the relatively low melting point of this fiber (∼ 145°C) has caused concerns regarding the effect of temperature rise during the impact/penetration process on the performance as armor material. In this article, an analysis of temperature rise in projectile and the fiber composite during the impact/penetration process is described. Combining the simulation of impact deformation by finite element analysis and the simulation of temperature rise by a finite difference approximation of the related dynamic equations, the temperature rise caused by the projectile/composite interaction was estimated. Results show that there is a significant temperature rise at the projectile/composite interface due to the friction but that the short length of time involved in the process and the low thermal conductivity of Spectra fiber composite keep the temperature rise in a very small region (in the order of 0.001 cm) around the interface during the impact/penetration process. Consequently, the volume that is affected by the temperature rise is very small, in the order of total 0.001 cm3 around the projectile, and this is too small to generate any detectable effect on the armor performance. After the projectile is stopped, however, substantial heating of fiber composite can occur under specific conditions as the result of heat flow from the hot projectile embedded in the composite. This heating of fibers, however, is a postmortem effect and hence inconsequential to the ballistic performance of the composite armor.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 59
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 60
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 190-200 
    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 mathematical model of a polycondensation reactor that can be used in the final stage for poly(ethylene terephthalate) (PET) is established and compared with experimental data obtained from a laboratory scale reactor with film renewal. Detailed side reactions are considered along with the diffusional removal of the small molecules through thin film. Among several kinetic constants, the polycondensation reaction rate constant k1(= k8) and diester group degradation reaction rate constant k7 have an influence over the degree of polymerization. The values of k1(= k8) and k7 for 0.05 wt% Sb2O3 were obtained as curve-fit values: (1) k1(= k8) = 3.4 × 106 exp(- 18.500/RT′) (L/mol-min); (2) k7 = 1.3 × 1011 exp(- 37,800/RT′) (min-1). Effects of the film exposure time, reduced pressure of vacuum, temperature, the initial terephthalic acid (TPA)/ethylene glycol (EG) mole ratio, the initial degree of polymerization, and catalysts were well explained by the model.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 61
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 209-212 
    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: Entrance pressure losses for the creeping flow of a power-law fluid are calculated for an abrupt contraction of ratio 2, 4, 8 and ∞ for both the axisymmetric and planar cases using P2P1 and P+2P1 finite elements. Contrary to some earlier findings in the literature, the entrance pressure loss obtained by using the two different types of finite elements, both of which satisfy the Babus̆ka-Brezzi condition, are found to converge to the same results. The present results also confirm that the variational method of Duda and Vrentas gives excellent upper bounds for both the axisymmetric and planar cases with infinite contraction ratio.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 62
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 405-413 
    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 curing of epoxy-amine polymer has been modeled by the reaction of functional groups, and the mole balance of these is governed by a set of six nonlinear differential equations. In this work, we have first developed a complete analytical solution for isothermal curing. For nonisothermal curing, we have divided the domain of hydroxyl group concentration β into small increments Δβ and adopted our analytical results for this domain. In addition, we solved the energy balance equation analytically and obtained the temperature rise for Δβ. We have compared our results with those obtained from the Runge Kutta numerical solutions. We have shown that our semianalytical technique is about a thousand times more efficient and faster.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 63
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 513-518 
    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 shear test is proposed as a complement to the tensile test in order to characterize the short time mechanical behavior of thermoplastic polymers. The proposed test geometry makes the test easy to perform and to evaluate and gives relevant information about anisotropy, plastic deformation, crack initiation, and propagation properties. Three different materials have been tested and the results are discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 64
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 500-506 
    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: Material property models for poly(etheretherketone) (PEEK) have been combined with a residual stress model to provide a means for investigating the effect of crystallization process on the residual stress development in semicrystalline materials. The analysis shows that crystallization causes an increase in the residual stress levels. This increase is affected through an increase in the resin modulus values and through the resin modulus build-up at higher temperatures. The shrinkage due to crystallization was found to have no effect on the residual stress development in neat PEEK.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 65
    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: Temperature sweeps of dynamic viscoelastic properties have shown that phydroxybenzoic acid (PHB)-based liquid crystalline polyesters, specifically in this case those copolymerized with poly(ethylene terephthalate) (PET), can be subjected to considerable supercooling if initial heating curves are compared to subsequent cooling curves, indicating that this type of material can be in quite different states even at the same temperature, depending on thermal history. Utilizing this supercooling behavior, viscoelastic properties of a 60 mol% PHB/40 mol% PET material produced by Unitika were monitored before and, particularly, after large-scale shear deformation to determine how potential structure changes induced by the shear are reflected in viscoelastic properties immediately, and with time. According to dynamic viscoelastic temperature sweep data four quite different initial states were employed including conditions with, as well as largely free of, crystallites. However, in all cases, post-shear monitoring showed decreased G′ and G″ values with almost no evidence of return towards initial values within approximately 25 min. These results, in addition to furthering somewhat the fundamental understanding of the flow and relaxation properties of liquid crystalline polymers, may be useful in polymer processing, where large-scale shear deformations employed in forming processes appear to be capable of changing considerably the subsequent behavior of such materials.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 66
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 507-512 
    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 thermodynamic model was proposed to correlate the phase behavior of a swelling polymeric gel (vinyl alcohol-sodium acrylate copolymer) and the volume phase transition in alcohol (methanol, ethanol or propanol)-water solutions. The model is based on the Flory-Huggins formula for polymer solution coupled with the osmotic pressure by rubber elasticity proposed by Flory. The volume change behavior and the equilibrium concentrations inside and outside the gel were successfully correlated using the present model.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 67
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 528-531 
    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: Terpolymerization was investigated by dilatometry for zincacrylate (ZnA2), acrylonitrile (AN), and styrene (St), radically initiated by a As2S3-styrene complex (I) in dimethyl sulphoxide (DMSO), at 90 ± 0.1°C for 1 h under inert atmosphere. The system follows non-ideal kinetics, due to primary radical termination as well as a degradative chain transfer reaction. The kinetic expression for the system is Rpα(I)0.27 (St)0.31 (AN) 0.22[ZnA2]0.12. The value for the activation energy and kp2/kt are 55 kJ mol-1 and 1.87 × 10-7 1 mol-1 s-1 respectively. The terpolymer has been characterized by IR and NMR spectroscopy. The thermal stability and solubility of the terpolymer have also been studied.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 68
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 69
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 551-558 
    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 intermeshing counterrotating twin screw extruder is widely used for compounding, devolatilization, blending, and reactive extrusion. A fluid dynamics analysis package-FIDAP, using the finite element method, was implemented to simulate the 3-D flow patterns in the region of conveying elements and shearing discs of a Leistritz LSM30.34 twin screw extruder. The rheological behavior of the fluid was described by a power law model. The flow fields were characterized in terms of velocity profiles, pressure distributions, shear stresses generated, and a parameter λ quantifying the elongational flow components. The influence of screw rotational speed and axial pressure difference on the flow characteristics was also analyzed. A comparison between the flow characteristics in the shearing discs operated in a corotating or counterrotating mode was also presented.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 70
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 532-540 
    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 model for the phase distribution and evolution of the heterogeneous (suspension) polymerization of vinyl chloride is presented. Experimental information on pressure, temperature, and conversion has been obtained from a 34 liter bench reactor reproducing reaction conditions and product properties typical of industrial operation. A calculation procedure based on simple plant data is proposed for the description of the phase compositions and their evolution over the entire process. Results based on classical Flory-Huggins theory of solutions are presented and compared with existing data.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 71
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 559-569 
    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 mathematical model is presented for the computer simulation of multilayer flow of polymer melts in coexitrusion. The proposed model can handle an arbitrary number of layers. The viscosity of each layer is shear-rate and temperature dependent. Given the material properties, die dimensions, and process conditions, the model determines the flow field throughout the die gap. Computer simulations and experimental data are presented for a three-layer polyester/EVA/polyester film coextrusion, with emphasis on the interfacial instability and its effects on optical properties of the film. The rsults are discussed in the context of the critical interfacial shear stress criterion that has been proposed by Schrenk, et al. (1) for the onset of interfacial instability. It appears that elasticity differences between layers contribute to the interfacial instability. It is conjectured that minimizing interfacial shear stress and matching elasticities of adjacent layers is an appropriate criterion in coextrusion analysis.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 72
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 541-550 
    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 simple unified lubrication approach has been proposed to design a coat-hanger die that can deliver wide and uniform liquid sheets. This approach requires that the wall stress in the manifold be constant. With this constraint, any inelastic non-Newtonian fluid model can be used to describe the liquid motion inside the die. Fluid models that can represent the pseudoplastic or viscoplastic behavior of polymeric liquids have been selected for illustration. A general equation that can be solved to determine the effect of production variations on flow uniformity inside the die has also been derived.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 73
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 570-579 
    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 paper we address the aspects associated with shear modification of low density polyethylene by extrusion. By successive passes of the polymer through an extruder it can be shown that both the melt viscosity and melt elasticity are reduced by shear modification. These reversible variations are not accompanied by significant changes in molecular weight distribution. The major effects of extrusion are to decrease the amount of elastically effecitve material. Study of proton relaxation times at 150°C shows that the melt comprises regions of relatively ordered, entangled, and unentangled polymer. Shearing reduces the proportion of more ordered material. The elastically effective anchors that are reduced by shearing are regions with restricted segmental mobility rather than conventional entanglements or intermolecular knots. Successive extrusions produce a relatively small decrease in the number of such constraints to molecular motion. Repeated shearing has a diminishing effect on the proportion of more ordered material in the polyethlene melt. This parallels observations of the effects of repeated shear modification on the properties of polyethylene films and other extrudates.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 74
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 585-597 
    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 paper presents the design and analysis of a process control strategy for a reactive extrusion polypropylene degradation process. The primary control objective is to continuously produce polypropylene with desired properties (viscosity) despite variations in the properties of the feed material. The viscosity of the polypropylene, measured using an In-line Wedge Rheometer, is controlled by manipulating the feed concentration of the peroxide which acts as the initiator for the degradation reaction. An empirical model of the reactive degradation process is developed which describes the process dynamics and the characteristic process disturbances. Minimum variance (MV), constrained minimum variance (CMV), and pole placement (PP) controllers are first evaluated and compared in simulation. Then, a pole placement controller is implemented on the actual reactive extrusion process, with results being presented for the response of the controlled process to load disturbances due to feed material changes.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 75
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 76
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 580-584 
    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 sliding plate rheometer has been developed to measure the normal thrust of a molten plastic in large amplitude oscillatory shear. The normal thrust of a molten plastic in large amplitude oscillatory shear is a significant nonlinear effect that has previously been unobtainable. Normal thrust measurements may now be used to help understand and characterize nonlinear viscoelastic behavior inherent in most molten plastics. The new rhemoeter incorporates a piezoelectric pressure transducer in a very stiff plate that minimizes compliance. Normal thrust measurements with cone and plate rheometers are made by measuring the total force on the plate (or cone) and are subject to error due to edge effects. The new rheometer measures the local pressure in the sample and is therefore unaffected by sample size or edge effects. Normal thrust measurements in large amplitude oscillatory shear are reported for both molten Phillips TR480 high density polyethylene pipe resin which contains 2% by weight of carbon black filler and IUPAC LDPE X. Crosstalk due to shear stress on the active face of the pressure transducer causes signal error which for oscillatory shear is filtered out using a discrete Fourier transform.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 77
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 613-624 
    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: At 75/25 concentration ratio, bisphenol a polycarbonate (PC)/styreneacry-lonitrile copolymer (SAN) blend has poor impact resistance compared to PC/ABS. A rubber phase methacrylate-butadiene-styrene (MBS) of core/shell type was dispersed in PC/SAN blend. The morphology of the unmodified and modified blend was investigated. The influence of the acrylonitrile ratio in the SAN on the microstructure was studied. It clearly shows that core/shell resides at the interface between PC and SAN. It seems that core/shell particles enhance the adhesion between the different phases. Their presence influences the interface mobility; i.e., the coalescence of the dispersed phase observed in pure PC/SAN is considerably reduced when the MBS particles are added. The impact resistance of the samples was correlated with the morphology.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 78
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 598-612 
    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 paper presents the development of a model for free radical initiated polypropylene degradation during reactive extrusion that combines a kinetic model of the polypropylene degradation reaction with a simplified model of the melting mechanism in the extruder. The free radical initiated degradation of polypropylene is characterized by a narrowing of the molecular weight distribution (MWD) and a decrease in the molecular weight averages. A high temperature SEC is used to determine MWD's for three different commercially available polypropylenes degraded at various initiator concentrations in a 1.5 inch single screw extruder (L/D = 24:1). The predictions of the kinetic model alone and the combined kinetic-melting model are compared with the experimentally determined MWD's and molecular weight averages for the degraded polypropylenes. The predictions of a modified kinetic model that includes the possibility of termination by combination are also examined. The kinetic-melting model is found to provide significantly improved predictions of the experimentally determined MWD's and molecular weight averages in comparison to the original kinetic model. A viscosity-molecular weight relationship is also developed, which is then used to determine the gain of the degradation process as a function of the initiator concentration from the molecular weight averages predicted by the kinetic-melting model. Earlier work has shown such prior knowledge of the process gain can be used to significantly improve the performance of process control schemes for the degradation process.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 79
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 625-631 
    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 curing and vitrification effect during the reaction of ATBN modified epoxy resin was studied through the dynamic differential scanning calorimetry method and a new reaction kinetic equation containing generalized WLF equation was developed to describe the reaction rate at both glassy and rubbery state. An autocatalytic mechanism was found to describe adequately the cure kinetics of the rubber modified epoxy resin and the overall order of reaction was assumed to be 2. The kinetic parameters were determined from the DSC data through the Marquardt's multivariable nonlinear regression method and Runge-Kutta integration technique. The presence of rubber indicated minor effect on the cure kinetics of epoxy resin. The Arrhenius type viscosity function was employed to establish a relationship between viscosity data measured by RMS and chemical conversion calculated from the reaction kinetic equation.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 80
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 642-649 
    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: Polyurethane foam formation involves both polymerization and expansion processes. The dynamics of the water and R-11 blown foams depend on the rates of chemical and physical blowing processes, along with the rate of viscosity increase of the reacting mixture. Experiments were carried out to study the dynamics of free rising, water and R-11 blown rigid polyurethane foams. The density and temperature change during the foam formation were monitored. A theoretical model was developed to predict the density and temperature variation with time. In the model, the physical blowing agent (R-11) evaporation process is assumed to be heat generation-controlled and the carbon dioxide generation process to be controlled by the rate of the water-isocyanate reaction. The kinetic parameters of the reactions of isocyanate with polyol and water were obtained separately and were asssumed to be independent of each other. The water-isocyanate reaction appears to follow first-order kinetics with respect to concentration of water. The theoretical predictions of the model show good agreement with the experimental data for density variation with time. The model predictions for temperature rise also match experimental data, except at the later stages of foaming when it is found to be slower than the experimental measurements. However, this deviation does not affect the dynamics of density change since it occurs after the completion of the expansion process.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 81
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 657-664 
    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 good extrusion die must distribute the polymer melt in the flow channel such that the material exits from the die with a uniform velocity and temperature. Coathanger dies are commonly used for the extrusion of plastic sheets and films. The die is usually provided with a straining bar allowing a regulation of the flowrate in the case of a poor design. But this, in turn, can affect temperature uniformity. Therefore, the design of coathanger die is a complex task which is mainly accomplished by trial and error in industry. Analyses of the flow in coathanger dies have been reported in the literature. Analytical and numerical approaches are used to solve this problem. The first one involves many simplifying assumptions: the most important ones being the unidirectional and isothermal flow of the polymer. Most numerical methods deal with a 2-D geometry, but only a few of them have considered the non-isothermal flow. A new model has been developed using a modified FAN method (Flow Analysis Network introduced by Tadmor) for the calculation of the 2-D flow, coupled with a finite-difference scheme for the calculation of temperature. The overall model can run on a PC with only a few minutes of calculation. Good agreement was obtained between experimental data and simulations.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 82
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 650-656 
    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 finite element model named Corrected Slice Method (CSM) has been developed to cope with three-dimensional vacuum cooling calibrator problems. Such problems appear whenever the cooling channel lay-out comprises transverse channels in the calibrator. The CSM is an extension of the 2D approach (8), which takes into account the axial heat fluxes within the calibrator. The proposed model was validated by comparing the numerical results obtained on a test problem with a rigorous finite element approach. Moreover, a real complex profile-calibrator system was simulated in order to illustrate the full performance of the porposed method.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 83
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 665-670 
    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 use of bend testers for the determination of critical strains in the study of environmental stress cracking has been assessed. Using the combination of polystyrene in ethanol, various factors affecting the measurement of critical strains were investigated, including the strain applied during the bend testing, the time of immersion in the liquid prior to straining, the surface finish, and the extent of physical aging. It was concluded that the best determination of critical strain is the strain at which a sample just shows signs of crazing, rather than the strain at the outer edge of a band of crazes. The measured value of critical strain increases with increased prior immersion time, decreased surface roughness, and decreased physical aging time. Reasons for these variations are discussed. It is concluded that although the use of bend testers is valuable for qualitative testing, careful testing methodologies need to be adopted for it to be a useful quantitative test.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 84
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 632-641 
    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 dynamics of R-11 blown polyurethane foam formation depend on the rates of viscosity increase of the reacting mixture and R-11 evaporation, and both are controlled by the polymerization process. Detailed experiments were carried out to study the dynamics of foaming and the measurements made included the cream and rise times, the density change of the expanding foam with time, and the temperature rise during reaction. Dynamic temperature measurements at different points in the foaming mixture were also made to study the spatial variation of the temperature in the foam. The experimental results showed the rate of foaming, the final density, and the maximum temperature decreased with increasing R-11 concentration. The heat losses from the foam were also found to be significant towards the later stages of foaming when density was low. Theoretical models were developed to predict the temperature and density change with time and spatial variation of temperature in the foam due to heat losses, by considering the foaming dynamics to be either heat generation controlled or heat and mass transfer controlled. In the former, the foam was assumed to be a pseudohomogeneous phase and the approach was similar to that of Rojas, et al. (5). New features accounted for in the model were dilution of the reactant concentration due to the presence of liquid blowing agent and heat loss from the foam due to radiation. While excellent agreement between theoretical predictions and experimental results was obtained for temperature variation with time at different locations in the foam, the model gave a much sharper reduction in density with time as compared to the experimental data. In the second model, the rate of foaming was assumed to be controlled by the rate of heat and mass transfer to a single bubble in the foam. Assuming a film model for heat and mass transfer, the theoretical predictions for both temperature and density were found to be in very good agreement with experimental data.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 85
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 821-826 
    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: When diffusion coefficients are measured with the cup method, the exposed area is often less than the area of the sample. Because of this masking effect the measured diffusion coefficient is overestimated. The present article presents simple formulas based on two-dimensional analytical solutions to correct for this in cylindrical cup samples. Different cases of anisotropical diffusion are dealt with. The error in the analytical solutions is determined by numerical computer simulations.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 86
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 815-820 
    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 comparative study of warpage, global shrinkage, and residual quench stresses developed in rotational molding is made for a series of thermoplastics including various polythylenes, polypropylene, polyamide-6, polycarbonate, and polystyrene. The influence of rate of quench on uniaxial stress strain and impact behavior of rotomolded parts was also studied. Generally, warpage, global shrinkage, and residual stresses increase with increasing quench rate for all the polymers. Further, the levels of warpage and global shrinkage increases with extent of crystallization, i.e., products from glassy polymers exhibit little warpage and those from highly crystalline polymers are highly warped. Increasing rate of quench tends to increase elongation to break and impact strength.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 87
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 799-803 
    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: Measurements of melt strength and breaking stretching ratio of several blends of thermoplastic polymers with liquid crystalline polymers are presented. The melt strength behavior depends not only on the viscosity of the blends but also on the temperature dependence of the viscosity. In particular, even if the viscosities of the blends are, at the extrusion temperature, lower than that of the thermoplastic matrices, the melt strength can be larger than that of the pure thermoplastics if its viscosity-temperature curve exceeds that of the matrices far from the solidification temperature. This behavior allows one to spin or film blow these blends despite the low viscosity.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 88
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 804-814 
    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 mathematical model of the high pressure polymerization of ethylene in tubular reactors was tested with experimental data obtained from an industrial size tubular reactor. Series of experiments involving changes in operating conditions were carried out, and process data and polyethylene samples were collected. The collected samples were characterized for their molecular weight distributions and various rheological material functions involving shear and extensional flows. The findings of the model were compared against the generated process data and the molecular weight distributions of the samples. The determined rheological behavior exhibited strong dependence on the primary characteristics of the resins. Overall, this study should introduce a better understanding of the interactions between high pressure reaction conditions and the primary properties of polyethylene, including moments of molecular weight distribution and extent of branching on one hand and the interrelationships between primary properties and the rheological behavior of the high pressure polyethylene product on the other hand.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 89
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 827-834 
    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 Galerkin finite element method has been applied to study the three-dimensional flow field of power-law fluids inside an extrusion die. Two inlet designs, i.e., center-fed and end-fed, have been considered. The effects of inertial force as represented by the Reynolds number Re, inlet geometry, and the power-law index n on lateral flow uniformity and vortex formation in the entrance region have been examined. A flow visualization technique has been carried out to experimentally verify the theoretical prediction of the three-dimensional flow field inside a die. It has been found that increasing Re or decreasing n will deteriorate flow uniformity. Depending on the direction of the inlet jet stream, the inertial force may create a flow peak in the central region of a center-fed die, or the maximum flow rate will appear close to the end of the die for an end-fed die. For highly shear-thinning fluids, lower flow rates are always observed close to the end of the dies. It is concluded that creating a plug flow in the inlet tube of the extrusion die is advantageous for both center-fed and end-fed designs.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 90
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 835-846 
    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 two-phase model is presented for simulating the post-filling stage of injection molding of amorphous and semicrystalline materials. A finite-element scheme with quadratic shape function for the pressure is proposed. The melt is considered in terms of Hele-Shaw flow for a non-Newtonian fluid using a modified-Cross model with either an Arrhenius-type or WLF-type functional form to describe the viscosity under nonisothermal conditions; the compressible behavior of the polymer is assumed to obey either a double-domain Tait or single-domain Spencer Gilmore equation of state. The interfacial energy balance equation including the latent-heat effect for semicrystalline materials is coupled with the transient energy equation for the solid and melt phases in order to predict the solidified layer and temperature profile. Two well-characterized materials, namely a commercial-grade PP and PS, were used in the present work. Good agreement is obtained between the present simulation and experimental pressure traces from this study and from previous investigation in the literature. The effects of compressibility, viscosity model, and thermal properties upon the predicted pressure field are also considered.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 91
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 92
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 93
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1148-1156 
    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 have generated microcellular polymeric foam structures using a pressure induced phase separation in concentrated mixtures of supercritical CO2 and poly(methyl methacrylate). The process typically generates a microcellular core structure encased by a nonporous skin, the thickness of which decreases with increasing saturation pressure. This trend can be described by a model for skin formation that is based on the diffusion rate of gas out of the sample. Significant density reductions on the order of 30 to 70% can be achieved by changing the pressure and temperature conditions in the foaming process. There are several ways in which the saturation pressure affects the average cell size, with the net effect that cell size decreases sharply with increasing pressure above 2000 psi, leveling out at higher pressures. Cell size increases with increasing temperature from 40°C to 70°C. A model for cell growth, based on a cell model of Aremanesh and Advani, modified to include the effect of CO2 on model parameters, reproduces these trends.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 94
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1161-1172 
    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: Multiobjective dynamic optimization has been carried out on a nonvaporizing nylon 6 batch reactor. Three objective functions have been identified, viz., minimization of the concentration of unreacted monomer in the product, minimization of the dimer concentration, and minimization of the reaction time, for producing polymer having a specified value, μn, d, of the number average chain length. Two problems have been studied in this paper, each consisting of two objective functions taken from the above set. Pareto solutions have been generated using an algorithm based on Pontryagin's minimum principle and the method of Lagrangian multipliers. The effects of various physical and computational parameters have been studied, and methods have been developed to overcome the numerical difficulties that arise during the solution. The Pareto sets so generated can be coupled with the surrogate worth trade-off (SWT) method, which facilitates interaction with a decision maker (DM). The optimal temperature histories obtained for the two problems studied are quite different and suggest that one must solve the three-dimensional problem in which the vector objective function incorporates all three objective functions. Results from the present study could be used as starting guesses to converge rapidly on the solution of the three-dimensional problem.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 95
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1187-1195 
    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 entrance pressure drop during extrusion cooking of corn grits was measured using a cylindrical die viscometer attached to a single screw extruder and compared with results obtained using low-density polyethylene (LDPE). The cylindrical die viscometer had a length to diameter ratio of 40 with half-entry angles of 30, 37.5, 45 and 90° with the horizontal. The entrance pressure drop at the die was measured as a function of extrusion temperature, product moisture content and the die entry angle. Results indicate that the flow behavior of corn grits and the entrance pressure drop were affected by product moisture content, process temperature and the shear history in the extruder. Entrance pressure drop also increased with wall shear stress for plastic melt, but for food biopolymer, the increase was observed provided shear history effects were minimized. Entrance correction increased with apparent shear rate for LDPE, but the reverse was true for corn meal. Using Cogswell's analysis, corn grits exhibit severe extension thinning behavior in entry flow.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 96
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1173-1186 
    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: Guidelines are developed for molding large composite parts via structural reaction injection molding using glass preforms and polyisocyanurate resins. These are based on numerical simulations of the simultaneous heat transfer and reaction kinetics of a commercial system during and after mold filling. Premised requirements are that resin does not gel before the mold is filled, yet, reactions are sufficiently vigorous to approach completion. An existing mechanistic kinetic model is used and material parameters found from a chemical kinetics study employing an insulated cup. It is found desirable to use a high mold temperature and a low preform temperature in molding. Nondimensionalization of the governing equations reveals the existence of a Nusselt number (Nu), which describes the relative importance of heat transfer between resin and glass relative to thermal diffusion to the mold wall. With a Nusselt number of about 50 or higher it is possible to use the cooling capacity of the preform to extend gel time. The magnitude of Nu is influenced by part thickness, glass fraction, strand diameter, and flow velocity. Thus, the effect of the preform on extending resin gel time is within control of the molder.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 97
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1196-1201 
    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 detailed study of the effect of several extrusion variables was made on the rheological and thermal properties of Delrin II acetal homopolymer and Zytel 42 polyamide 66 materials. A 63.5 mm Davis Standard extruder was used to measure the effect of screw design, screw rpm, die and head pressure, and melt temperature on the rheology of acetal and nylon 66 resins. A single stage metering screw was used to determine the effect of screw geometry and viscous heating on the melt viscosity breakdown and the rate of degradation of each polymer. The melt temperature was measured in the melt stream in the channel and correlations are shown between ideal melt temperature predicted from the rheology data and the actual loss of properties of each polymer due to viscous heating. The paper also discusses how to measure the melt temperature accurately in extrusion, and to use it as a key indicator to optimize the extrusion process, and to control the rheology, thermal stability, and the molecular weight of a polymer during processing.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 98
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1202-1210 
    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 article, we investigate the effect of weld lines on the tensile mechanical properties of unmodified and copolymer modified high density polyethylene (HDPE) and polystyrene (PS) blends. The homopolymers were melt blended in the proportion of 20 wt% HDPE and 80 wt% PS using a twin screw extruder at a temperature of 200°C. The results show that the mechanical properties are generally lower when weld lines are present. The decrease of the mechanical properties is much more pronounced for the blends. The addition of small amounts of a commercial styrene/butadiene copolymer significantly improves the strength and the elongation at break of this blend. An optimum copolymer concentration was observed at 3 wt%. This value coincides with the interphase saturation concentration of the copolymer obtained from the analysis of the DMTA (dynamic mechanical and thermal) properties of the blends. The copolymer was also found to induce important changes in the morphology of the blend. The interdiffusion of the polymer fronts in the weld region was also improved by the presence of the copolymer. It is believed that these two aspects contribute to the enhanced properties obtained with copolymer modified blends in presence of weld lines. An important effect of the injection temperature on the tensile strength and the elongation at break of welded samples with copolymer modified blends was observed. The effect of mold temperature on these properties was less important mainly at low injection temperatures. Only a slight effect of these two parameters was observed for the tensile modulus in the range of mold and injection temperatures considered in this study.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 99
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1211-1218 
    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 injection molding of substrates for optical discs, precise transcription of pits and grooves is very important. For high-density optical discs, molding transcription for minute grooves with widths on the sub-micron level is required. In this paper, in order to clarify the relationship between molding conditions and transcription quantitatively, transcription of minute rectangular grooves (width 0.55 μm, depth 70 nm) in injection molding of polycarbonate resin was studied. The relationship between molding conditions and the transcription heights was verified. And, by introducing the equivalent thickness of the vitrified layer concept, a transcription model related to the minute groove width is proposed. This equivalent thickness of the vitrified layer is estimated to be 100 to 150 nm at the point of filling completion under a certain molding condition. Also, using the above description of the equivalent thickness of the vitrified layer, it is possible to estimate the extent of transcription under the various molding conditions.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 100
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...