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  • Chemical Engineering  (770)
  • 2000-2004
  • 1980-1984  (460)
  • 1965-1969  (310)
  • 1981  (460)
  • 1966  (310)
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  • 2000-2004
  • 1980-1984  (460)
  • 1965-1969  (310)
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  • 1
    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 is an account of some studies of the mechanism of degradation of an uncrosslinked polyurethan prepared from poly(propylene oxide) (PPO) and 2,4-tolylene diisocyanate (TDI) at temperatures up to 320°C in a vacuum or inert atmosphere. Fractionation of polymers before and after degradation provides information about the mechanism of degradation since the molecular weight distributions obtained are dependent on the mode and sites of bond scission. A recent publication describes the column elution method of fractionation developed for undergraded and slightly degraded PPG-TDI. PPO-TDI gives essentially most probable molecular weight distributions at an initial intrinsic viscosity [η] of ∼ 0.68 dl/g and also after degradation to [η] ∼ 0.24 dl/g. This invariancy of the distribution strongly suggests a randon scission process. Other types of degradation, e.g., free-radical unzipping initiated at the chain ends, could also give invariant most probable distributions. However, such depolymerizations would be accompanied by much larger extents of volatilization than were observed for these polymers (〈5% volatilization).
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  • 2
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 6 (1966), S. 65-70 
    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: Moisture present in epoxy anhyride composites may hydrolyze the anhydride and cause major changes in the mechanical and chemical properties of the final composite. Heat distortion data and infrared spectroscopy are used to analyze the changes caused by the presence of the moisture. As the concentraton of water is increased, there is a decrease in the heat distortion or gass transition temperature. The decrease is due to a change in the crosslinking network and is caused by the reduction of the functonality of the epoxy group for acid as compared to the anhydride. Where rigid specifications must be met it is essential that the moisture level in the fillers, resins, etc. be kept constant.
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  • 3
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 6 (1966) 
    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
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  • 4
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    Polymer Engineering and Science 6 (1966), S. 117-123 
    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: There is considerable literature on the behavior of polyethylene below 200°C and above 400°C. This paper presents results on both high and low density polyethylene between 2000 and 400°C, a range of practical import for various fabrication and processing steps. Practical exposure times may be short and the experimental procedures were designed to give meaningful results for times as low as 1 min. The principal effects are chain-session and oxidation. Session was isolated by applying an atmosphere of pure nitrogen and proved uite shlow at 300°C but rapid at 400°C. The course of scission and produces discoloration, odor, and rising carbonyl content. A brief discussion is given of the role of diffusion in oxidation.
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  • 5
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    Polymer Engineering and Science 6 (1966), S. 97-112 
    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 application of silane coupling action produces significant improvements in physical properties in various thermpolastic resin systems. Both glass-reinforced thermoplastics and the more conventional filled thermoplastic resin systems were studied. An order of specificity between resin and coupling agent exists for thermoplastic resins similar to that of thermosets. The interaction with thermosets is considered copolymerization, wereas that with thermoplastics is not yet clearly defined. The silanes are incorporated by pre-treatment (best for glass reinforcement) or by addition during normal compounding. Fillers are added for a specific result, often with sacrifice of physical strength. Data presented show that silane addition upgrades filled thermoplastics to the level of clear resins and sometimes above. The effect of silanes on electrical properties of filled thermoplastics are also reported.
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  • 6
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    Polymer Engineering and Science 6 (1966), S. 127-130 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An optical method has been developed to provide quantitative results useful for characterizing the crazing of transparent plastics. The procedure consists of the detection of discontinuities in a beam of light that scans the specimen in a direction perpendicular to the line of crazing. The light is transmitted to a photomultiplier that is connected with an amplifying system and a recorder that provides a diagram of the light energy modulated by the lines of crazing. The specimen is scanner both before and after subjecting it to a treatment that causes crazing, and the crazing index is considered to be the difference between the area below the two curves.
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  • 7
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    Polymer Engineering and Science 6 (1966), S. 169-172 
    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: Many rigid PVC compounds show a sharp transition from tough to brittle fracture with decreasing temperature in impact testing, and this temperature becomes a criterion of compound quality in addition to the impact strength observed at specific temperatures. This BT (brittle fracture) has been investigated individuall in commercial and experimental elastomer modified rigid PVC compounds. Factors affecting the BT include speciman thickness, composition and processing conditions. Apparently the discontinuity in impact behavior is a sudden manifestation of a gradual change, resulting in a near ten-fold decrease in notched impact strength without any obvious change in properties. The BT provides a continuous scale for comparing impact properties of compounds, and is thus more versatile and sensitive than impact tests run at a single temperature.
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  • 8
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    Polymer Engineering and Science 6 (1966), S. 158-168 
    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 of polymer melts is normally laminar, but pseudoplastic in character. That is, flow rate increases in proportion to a power higher then 1, usually between 1.5 and 4, of the applied pressure difference. Viscosities are extremely high - more then a mollion times that of water - so considerable heat is generated in the flowing melt by viscous dissipation of flow energy. This mode of heat generation is put to good practial use in the screw extruder, a device that converts plastic pellets into hot melt for shaping into pipe, sheets, coatings and molded products. Equations are given for computing flow rates and viscous dissipation rates. Heating (except by viscous working) and cooling of polymers are slow processes because all these materials are poor heat conducts nad their extreme viscosities make convection impracticable. The princliples of heat transfer are reviewed, and the solutions are given for some transient-conduction problems frequenlty encountered in processing. Equations are given for judging the operation of extruders.
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  • 9
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    Polymer Engineering and Science 6 (1966), S. 182-184 
    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
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  • 10
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    Polymer Engineering and Science 6 (1966), S. 203-212 
    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: Tangential flow of a “power law” model fluid between two concentric cylinders is analyzed. A constant angular pressure gradient is imposed and one of the cylinders is rotating at a constant angular velocity. This type of flow is of interest in screw extrusion theory. The error in the superposition, i.e., linear addition of tangential pressure and drag flows, for a “power law” model fluid, is quantitatively calculated and plotted in the form of a correction factor. Tangential pressure flow is compared to a pressure flow between parallel plates and additional correction factor to account for the curvature is derived and plotted. The applicability of the “power law” model for flow of polymer melts in extruders is also discussed.
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  • 11
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    Polymer Engineering and Science 6 (1966), S. 198-202 
    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 article describes a general mathematical model summarized in the form of a computer program for the plasticating extruder. The model combines features of the metering-zone model previously published, the melting-zone model described in paper No. I of this series, and a feed-zone model based on an extension of known theories. It is based on theoretical models for each zone unified and improved by non-linear estimation to accurately describe the extrusion experiments.The mathematical model predicts temperature, pressure, and melt channel width profiles of the plastic being processed in the plasticating extruder as a function of design and operating variables of the machine. It enables for the first time the design of the whole machine based on temperature and pressure profiles, including new combinations of cylindrical and tapered roots.
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  • 12
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    Polymer Engineering and Science 6 (1966), S. 213-216 
    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 development of a fractional crystallization technique for characterization of polypropylenes with respect to stereoregularity is described. It is a simple technique which is attractive for routine analysis and under suitable conditions yields quantitative data with good reproducibility. Separation by fractional crystallization from hot xylene solution is shown to take place according to polymer crystallizability and is relatively independent of molecular weight. It thus represents an alternative and in some ways superior approach to the more commonly used fractional extraction method. Preliminary work indicates that the fractional crystallization method may prove of value in establishing correlations between the stereoregular nature of polypropylenes and their physical properties.
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  • 13
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    Polymer Engineering and Science 6 (1966), S. 244-247 
    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 density and tensile property changes in polypropylene resulting from various post-crystallization aging procedures are investigated with the aim of (1) establishing standard procedures for the evaluation of these properties and (2) determining which conditioning treatment will provide optimum tensile properties. The morphology and resultant tensile behavior of polypropylene are particularly sensitive to conditioning treatments in the temperature range 145-160°C. A procedure for compression molding plaques, carrying out isothermal annealing treatment in the 100-170°C range and gradual cooling is described. The dependence on annealing temperature of the density, elongation, tensile modulus and yield stress is given.
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  • 14
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    Polymer Engineering and Science 6 (1966), S. 260-262 
    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: Some earlier observations on the influence of molecular weight, plasticizer, and irradiation on the thermal conductivity of polymers is reviewed. Also some new data on polystyrene and some new calculations based on the theory of Hansen and Ho are presented. These data show almost a two fold increase in the thermal conductivity of polystyrene as the molecular weight goes from 900 to 100,000. Data on the moleculer weight effect on thermal conductivity appear to be consistent with the theoretical calculations.
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  • 15
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    Polymer Engineering and Science 6 (1966), S. 273-278 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Thermal oxidation in linear polyethylene is mainly confined to disordered regions in which scission reactions cause crystallization and eventual deterioration of mechanical properties. Gel formation is negligible at 100°C. As degradation proceeds, comparable changes occur in the intrinsic viscosities of melt and solution-crystallized liner polymers, indicating that chain folds are regularly arranged and are resistant to oxidative scission. Breakdown is much more extensive in branched and crosslinked polymers since crosslinking retards oxidative crystallization and branching increases the volume fraction of substrate ultimately accessible to oxygen.
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  • 16
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    Polymer Engineering and Science 6 (1966), S. 295-298 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: For a system of equivalent bonds undergoing random bond scission it is reasonable to assume that the rate of bond breaking (hence the rate of creation of new molecules) reported in the literature and data presented here demonstrate that the number of molecules created is not proportional to the time of thermal treatment hence they seem to belie this reasonable hypothesis. Other authors have adduced the presence of some non-equivalent bonds in order to account for the observed cruvature and still retain the hypothesis. Implicit in these arguments is the assumption of a steady-state concentration of reactive fragments. Our analysis explores the consequences of abandoning the steady-state assumption and shows that a quantitative explanation of the observed degradation behavior may be had by this means wihile still retaining the hypothesis of a constant probability of a bond being broken per unit time.
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  • 17
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    Polymer Engineering and Science 6 (1966), S. 248-254 
    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: Most polymers exhibit a very fluid melt rheology during extrusion and can be distorted, drawn down, and cooled without building excessive residual stresses into the product. In contrast, rigid vinyl is usually extruded as a stiff, almost selfsupporting mass. Care must be taken to prevent the formation ot oriented stresses in the product which will be relieved during long periods of exposure resulting in dimensional instability and related loss of physical properties. A newly developed method of in-line annealing has shown to be an effective means of relieving oriented stresses developed during extrusion. By use of this instrumented technique, rigid vinyl products can be controlled to much tighter shrinkage specifications in a single step process, thereby eliminating post-annealing treatments.
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  • 18
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    Polymer Engineering and Science 6 (1966) 
    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
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  • 19
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    Polymer Engineering and Science 6 (1966), S. 282-284 
    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
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  • 20
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    Polymer Engineering and Science 6 (1966), S. 299-305 
    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: Residence time distribution (RTD) is a spectral property of contiuous chemical reactors. Batch reactors may be viewed as having “monodisperse” residence time distributions. This article discusses molecular weight distributions (MWDs) of polymeic materials formed in continuous and in semicontinuos process and how they are affected by reaction time distributions. All synthetic high polymers, even those Prepared in batch reaction, possess a MWD which may sometimes, for a given monomer, be altered chemically by a proper choice of catalyst and diluent. An interesting concept suggested by the present work is the prospect of “tailoring” the MWD for a given monomer-catalyst-diluent system physically by selecting appropriate reactor conditions. Hence, althought this work involves analysis the results may provide a guide to synthesis.
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  • 21
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    Polymer Engineering and Science 6 (1966), S. 369-372 
    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: Commercial films, elastomers, and fibers have valuable in-use properties below 300°C. Astronautic requirements, however, may evaentually call for materials that withstand 500 hrs at 300°C or 100 hrs at 500°C while fully retaining their useful properties. The most significant advances in the synthesis and preparation of heat resistant polymer have been made since 1959 with new synthetic methods such as interfacial polymerization, cyclopolymerization, and intramolecular polymer post-cyclopolymerization, and intramolecular olymer post-cyclization reactions. It is the purpose of this paper to discuss the structural relationships among those heat resistant, orgainc polymers that were reported to give strong films and fibers. Those heat resistant polymers, which have not yet been fabricated into films and fibers are not included in this review.
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  • 22
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    Polymer Engineering and Science 6 (1966), S. 373-376 
    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: Monodisperse and polydisperse polystyrenes of equal weight average molecular weight (Mw) are evaluated for melt flow behavior in an Instron capillary rheometer and for injection molding behavior in a 12 ounce in-line reciprocationg screw injection molding machine. The influence of molecular weight distribution on the shape of the flow curves is deconstrated over a wide range of shear rate and temperature. The influence is also reflected in injection molding behavior as defined by pressure to fill or flash the mold at a given melt temperature. Studies of capillary rheometer data for correlation with injection moling beghavior indicate poor agreement when low shear rate viscosity data are used. Good agrement is foun using high shear rate viscosity data in the range 103 to 104 sec-1 Striking crossover points on melt rheology and injection colding area diagram curvs are found with the monodisperse and polydisperse polystyrenes of the same M These crossovers shift with melt temperature and make possible the determination of a “controlling shear rate” for the injection molding process. This is found to be 3500 sec-1 for short shot and 6200 sec-1 for flash with the ASTM test specimen mold used in this study.
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  • 23
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    Polymer Engineering and Science 21 (1981) 
    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
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  • 24
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    Polymer Engineering and Science 21 (1981), S. 18-22 
    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 history dependent solubility model is generalized in accordance with the Dual Mode Sorption Theory to take into account a history dependency of effective water diffusion coefficients in epoxy resins, based on hypothesized microcavitational damage due to the combined effects of temperature and sorbed moisture. Sorption data presented in a different paper are analyzed in the light of a transport model in which part of diffusing molecules are completely immobilized in the formed microcavities. The nature of the hypothesized damaging process is in agreement with the diffusion coefficient depressions and solubility increases experimentally found and theoretically predicted by the model.
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  • 25
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    Polymer Engineering and Science 21 (1981), S. 23-31 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An experimental study was made of single fibers rotating and bending in Couette flow of a Newtonian liquid. A previous result for critical fiber buckling was re-tested and found satisfactory, and the transition between ‘springy’ and ‘snake’ rotation was delineated. The minimum radius, of curvature achieved during rotation in the “snake orbit” regime was measured as a function of fiber aspect ratio, Young's modulus, and fluid shear stress. Two correlations are presented which are constrained to satisfy limiting conditions for very stiff and very flexible fibers. Together with a result from thin rod theory, these correlations may be used to predict breaking conditions for fibers of known Young's modulus and ultimate tensile strength. Predictions are tested in experiments where two types of glass fiber are broken in suspension and found satisfactory. Results show that several reinforcing materials will probably break within the range of conditions covered by our experiments, or in a region which can be treated by extrapolation from our results.
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  • 26
    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 oxidative degradation of cold drawn highly oriented high density polyethylene is studied by IR spectroscopy. Both gamma and ultraviolet radiation sources are used. It is found that under gamma radiation the oxidative degradation, as determined from carbonyl formation, is reduced very significantly but that the trans-vinylene unsaturation in the polymer increases with draw ratio. Similar results are obtained for samples irradiated in vacuum or when the polymer is stabilized with a radical quencher. Annealing (with free-ends) of the samples restores the rate of carbonyl formation over and above that of the undrawn polymer although restoration after annealing with fixed-ends is not complete. There, is further increase in trans-vinylene development after annealing. In stabilized samples, the effect of annealing on carbonyl and trans-vinylene development appears to depend on draw ratio.Under ultra-violet radiation, the oxidative degradation of drawn and unannealed samples is also reduced with increasing draw ratio. The same effect is observed in stabilized samples. Annealing, once again, restores the rate of oxidative degradation to that of the undrawn polymer. The main unsaturation product during ultraviolet irradiation is the vinyl end group and its development is suppressed with drawing. During ultraviolet irradiation of unannealed drawn samples, cracks, generally perpendicular to the draw direction (intrafibrillar cracks) appear on the sample and with further irradiation they penetrate into the sample. In the case of stabilized and unannealed drawn samples, cracks parallel to the draw direction (interfibrillar cracks) appear first and continued irradiation results in the appearance of intrafibrillar cracks. These observations may have significance in modelling the fibrous structures obtained by drawing semicrystalline polymers.
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  • 27
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    Polymer Engineering and Science 21 (1981), S. 1-7 
    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 crystallization behavior of three IUPAC low density polyethylene samples has been characterized by thermal analysis. Their rates of crystallization only are directly correlatable with their film forming ability in film blowing technology. The IUPAC samples possessed essentially indistinguishable physical properties, including differential scanning calorimetry (DSC) melting curves and rheological characteristics, but their propensity for crystallization was found readily to parallel their film forming ability and other characteristics associated with end-use performance. The application of thermal analysis to assess crystallization is a unique diagnostic tool for measuring polymer film processability, which is well illustrated here using a few simple experiments made on the original polymer specimens and a polymer blend. Although all samples exhibit similar small-angle X-ray periodicities, the morphological differences assessed, particularly by microtomy-optical microscopy, correlate with, and complement, the results of phase transformation kinetics responsible for film properties. Fractography-scanning electron microscopy proves to be inferior to optical methods for revealing the morphology of these low density polyethylenes.
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  • 28
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    Polymer Engineering and Science 21 (1981), S. 47-52 
    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: Mixtures of two compatible polymers, poly(vinyl chloride) and poly(acrylonitrile-co-butadiene) containing 40 percent acrylonitrile, can be compatible with poly(vinylidene chloride-co-vinyl chloride), which is incompatible and partially compatible respectively with these two polymers. The crystalline melting temperature and relative heat of fusion of poly(vinylidene chloride-co-vinyl chloride) in blends are higher than those in the pure component. This is attributed to greater ordering of the polymer chains in the crystalline phases of the blends. Replacing the rubber by poly(acrylonitrile-cobutadiene) containing 30 percent acrylonitrile, shows that these three polymers, in which each pair is incompatible or at most partially compatible, also form compatible ternary blends. The crystalline melting temperature is higher and relative heat of fusion lower than those in the pure component. This is attributed to dissolving of parts of the polymer chains originally located in the crystalline phases in the amorphous phases of the blends.
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    Polymer Engineering and Science 21 (1981), S. 32-38 
    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: Films of low-density polyethylene, polypropylene, and rigid poly(vinyl chloride) were exposed for 1700 h to artificial aging in a Weather-O-Meter. Photochemical aging was characterized by tensile measurements. We noted that only ultimate properties are affected, whereas properties defined in the low strain range remain unchanged. The kinetics of strain and stress at break depend as much on the polymer's initial rheological characteristics as on the rate of the chemical degradation. The results show that aging results in localized chain breaking leading to defects at the supermolecular level. The average decrease of molecular weight does not seem to influence the mechanical behavior.
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  • 30
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    Polymer Engineering and Science 21 (1981), S. 53-56 
    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 has been carried out on the properties of a fast-curing two-part polyurethane sealant, and on its blends with other polymers, such as poly(vinyl acetate), poly(vinyl chloride) and poly(vinyl alcohol). Different substrates, such as Portland cement mortar, wood, and aluminum in three different thermal conditions were used. Tension tests by Universal Testing machine Model 1175 have been made, and stress-strain curves have been devised and discussed. A two-component fastcuring polyurethane sealant demonstrates good adhesivity for the supports mentioned. The elasticity of polyurethane sealants may improve even at low temperatures if mixing with other polymers.
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  • 31
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    Polymer Engineering and Science 21 (1981), S. 39-46 
    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: Thermoplastic interpenetrating polymer networks, IPN's, are defined as combinations of two physically crosslinked polymers. A styrene-b-ethylene-co-butylene-b-styrene (SEBS) triblock elastomer was combined with an ionomer prepared from a random copolymer of styrene, methacrylic acid, and isoprene (90/10/1 by volume), and subsequently neutralized. Two subclasses of the thermoplastic IPN's were identified. A sequential polymerization method yielded the chemically blended thermoplastic IPN's (CBT IPN's). Melt blending of the separately synthesized polymers produced the mechanically blended thermoplastic IPN's (MBT IPN's). Stress-strain and Rheovibron characterization revealed that the CBT IPN's exhibited greater tensile strength and higher elongation at break, but lower moduli than the MBT IPN materials of the same overall composition. Analysis of moduli data with the theories of Takayanagi, Davies, Budiansky, and Kerner disclosed more equal dual phase continuity for the MBT IPN's than the CBT IPN's at each composition. The low modulus of the more rubbery CBT IPN compositions was attributed to a decrease in the effective chain end-to-end distance between crosslinks in the elastomeric (EB) center block, brought about by the synthetic method.
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  • 32
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    Polymer Engineering and Science 21 (1981) 
    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
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  • 33
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    Polymer Engineering and Science 21 (1981), S. 57-63 
    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 real-time computer system is described which minimizes the total analysis time in gel permeation chromatography by automatically acquiring the data, performing the necessary calculations and displaying the molecular weight distribution and molecular weight averages as soon as the polymer peak has eluted. The calculation method described here is valid for linear homopolymers only, and does not include corrections for instrumental peak broadening. The experimental results show good reproducibility and precision. On-line changes of the constants and other parameters may be implemented by means of an auxiliary program which runs in parallel with the data analysis program. A system such as that described here is suitable for utilization as a measurement technique in process control applications. The programs are written in CORAL 66 for a Ferranti Argus 700 E computer.
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  • 34
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    Polymer Engineering and Science 21 (1981), S. 65-68 
    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: An approximate analytical solution is obtained for the flow rate-pressure drop relation for adiabatic capillary flow of a fluid with a pressure- and temperature-dependent viscosity. Neglect of the pressure dependence can result in large errors in the usual range of injection molding practice. The approximate solution follows from an exact solution of capillary flow with a viscosity that depends only on pressure.
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  • 35
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    Polymer Engineering and Science 21 (1981), S. 76-79 
    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 properties and processing characteristics of open-celled foams produced by leaching small NaCl particles from high density polyethylene has been investigated. In a random dispersion of salt particles in the polymer matrix a minimum volume loading of 40 percent was required to produce an open-celled foam. The time required to remove this quantity of salt with 50°C water was 100 min. The maximum porosity of the foam is limited to the maximum packing fraction of the salt. For randomly dispersed isotropic particles the maximum packing fraction is approximately 0.64. Because the composite rapidly loses melt strength as the filler content nears the maximum packing fraction, the practical upper limit of extruded foam porosity is approximately 0.60.
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  • 36
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    Polymer Engineering and Science 21 (1981), S. 86-92 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An experimental investigation into the performance in general and the melting behavior in particular of a single screw extruder running with a low density polyethylene power has been carried out and the results compared with those for a granular feedstock of low density polyethylene having similar melt properties. It was found that the tendency was for the output rate, pressure generated and specific power consumption to be lower for the powders, and that the removal of barrel heating near the feed hopper increased these parameters. Two melting mechanisms were observed in powder extrusion; one being the classic “Maddock” type, and the other such that the solid bed and melt pool were in reversed positions relative to the Maddock case. There was a trend for this latter mechanism to operate with low screw speeds, shallow channels and full heating. Melt initiation occurred nearer the feed end and melting was completed much more quickly with powders. An explanation of the mechanisms is proposed which is based on the observation of early melt initiation, and the industrial practices of feed zone cooling and increasing feed pressure generation to improve the performance of extruders running with powders are seen to be consistent with this proposition.
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  • 37
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    Polymer Engineering and Science 21 (1981), S. 80-85 
    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: Several rheological aspects of thermoplastic foam extrusion are described by a phenomenological model of the flow in an extrusion die. The macroscopic effects of the phase change, from a homogeneous polymer melt that contains a blowing agent, to a foam, are described in terms of two dimensionless parameters. α is defined as the ratio of the pressure gradient in the melt phase to the average pressure gradient in the foam phase. Θ represents the ratio of the pressure drop in the melt phase to the pressure drop in the foam phase. The position at which the phase change initiates, the exit contribution to the Bagley ends pressure correction, and the true wall shear stress in the melt phase are related to α and Θ. The quality of the foam produced is discussed in terms of the extrusion conditions and their effect on the foaming position in the die. It is demonstrated that the ends pressure correction cannot be neglected on the basis of a long die alone. Asymptotic conditions for which the phase change has negligible effect on the melt flow rate are predicted. α is calculated from the data of Han and Villamizar, who measured the pressure distribution in the die and observed the phase change directly. The prediction of α from theory is complicated by the lack of suitable constitutive relations for the foam phase. Since Θ only requires knowledge of the pressure at which the phase change initiates, it is relatively easy to evaluate.
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  • 38
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    Polymer Engineering and Science 21 (1981), S. 69-75 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An experimental and theoretical study was carried out to achieve a better understanding of bubble dynamics in foam extrusion through a converging die. For the experimental study, a number of converging channels were constructed of aluminum, with glass windows on both sides. Bubble dynamics in the flow channel were recorded on movie film as a gas-charged molten polymer was extruded. The dies had various converging angles (30, 45, 60, 90, and 150 degrees), and the polymer was polystyrene. As blowing agent, sodium bicarbonate (generating CO2) was used. It was found that the gas bubbles moving along the centerline of the channel grow initially at the upstream end of the die, and then start to collapse as the gas-charged molten polymer approaches the exit plane of the die. In order to help interpret the experimental results, a theoretical analysis was made of bubble dynamics in a converging channel, in which a thread-like bubble was assumed to flow along the centerline of the converging channel and the Coleman-Noll second-order fluid model was assumed to describe the rheological behavior of the polymer melt. Some mathematically convenient simplifying assumptions not-withstanding, the theoretical analysis corroborates the experimental observations. The practical significance of the present investigation is discussed in connection with controlling the cell structure in extruded foam products.
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  • 39
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    Polymer Engineering and Science 21 (1981), S. 93-99 
    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 method is given for selecting the “effective viscosity” for isothermal flow of non-Newtonian liquids in screw pumps or melt extruders. Effective viscosity is the Newtonian viscosity that would give the same screw-pump performance with non-Newtonian liquids at the same flow rate and speed. When effective viscosity is known, it can be inserted in performance equations for simple Newtonian flow. The analysis is restricted to shallow screw-pump channels with large aspect ratios and to shear stress/shear rate curves with modest curvatures when shown in a double logarithmic plot. The shear stress/shear rate curve is replaced by a power-law tangent to that curve in the domain of prevailing shear rates, but the analysis could be extended to more complex behavior. Curves are also included for calculating the efficiency of the screw-pump channel, which can be used to estimate the energy dissipated in screw-pumps. It is shown that efficiency decreases with decreasing power-law exponent.
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  • 40
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    Polymer Engineering and Science 21 (1981) 
    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
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  • 41
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    Polymer Engineering and Science 21 (1981), S. 105-112 
    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 process of melting individual polymer granules and then combining them into a homogeneous molten mass is examined. The granules are introduced into a high temperature fluid bath, heated as they move due to the polymer-fluid density difference and finally coalesce under the action of surface and gravity forces into a uniform polymer melt which can be used for extrusion, injection molding or other melt processing techniques. Theoretical models and analyses are presented to predict the time required to melt a granule in a particular polymer-fluid system and to have the molten granule coalesce into the developing mass of molten polymer. This latter time includes the time for the continuous phase fluid to drain between the approaching granule and the molten polymer-fluid interface and the time for the granule, once in contact with the interface, to be deposited to some specified depth in the bulk molten polymer. Design parameters for a particular embodiment of the process are presented. Experimental results obtained with a prototype device using mercury as the heat transfer medium are discussed.
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  • 42
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    Polymer Engineering and Science 21 (1981), S. 100-104 
    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: Finite element solutions are presented for developed, isothermal, power-law flow in an extruder channel, based on a variational formulation in helical co-ordinates. The success of the method in handling non-Newtonian flow in a deep, highly-curved channel is tested by comparison with experimental results. Operating characteristics were determired under virtually isothermal conditions for a screw with depth to diameter ratio 0.25 pumping an aqueous glucose solution containing high molecular weight hydroxyethyl cellulose. Shear stress and first normal stress differences of this solution were determined in a rheogoniometer. It was both highly shear-thinning and elastic. Computed and experimental screw operating characteristics agree well, except near closed discharge, where effects due to viscous heating and elasticity are tentatively suggested.
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  • 43
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    Polymer Engineering and Science 21 (1981), S. 121-123 
    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 model, based on an average elongational rate, correctly predicts qualitatively the effects of changes in all spinning parameters on the orientation of fibers spun from viscoelastic melts. The model may be extended to any extrusion process with an elongational character.
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  • 44
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    Polymer Engineering and Science 21 (1981), S. 113-118 
    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 technique for the electrical monitoring of polymerization reactions such as resin cure is described. The technique is based on the charge-flow transistor, which resembles a conventional metal-oxide-semiconductor field-effect transistor (MOSFET), but with a portion of the metal gate replaced by the resin under study. Electrical signals obtained from several resins undergoing cure are presented, along with an electrical circuit model that can account for the principal features of these signals. The dramatic change in signal shape during cure can be related to corresponding changes in both the real and imaginary parts of the dielectric constant.
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  • 45
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    Polymer Engineering and Science 21 (1981), S. 124-128 
    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: Methods of predicting and correlating thermal conductivity of polyethylene resins in solid and melt states are discussed herein. Dependence on crystallinity or density is estimated for the solid state by a form of Maxwell's equation for electrical conductivity. An equation is presented for predicting melt thermal conductivity based upon Bridgman's theory of energy transport and pressure-volume-temperature (PVT) data. The effect of pressure on melt thermal conductivity is calculated from the theory. The effect of pigmentation for near spherical particles up to approximately 2.5 volume percent is also correlated by a form of Maxwell's equation. Experimental thermal conductivities of unpigmented and pigmented polyethylene resins from 50 to 300°C are in good agreement with theoretical predictions and with literature data.
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  • 46
    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: Torsional Braid Analysis (TBA), like many other sample-supported techniques, measures the transition temperatures of a polymer deposited on an elastic support. It is shown here that any polymer transition found by the location of the maximum in the log decrement Δ (or loss tangent tan δ) of a composite shifts to lower temperatures as the rigidity (or modulus) of the elastic support is increased. The magnitude of this temperature decrease is larger for transitions at which a composite has a larger support-to-polymer rigidity ratio. In general the above conclusions hold even with unsupported systems if the rigidity (or modulus) of the sample can be increased without interfering with the polymer domain under investigation, for example, by crosslinking one of two phases of microphase-separated co-polymers.
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  • 47
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    Polymer Engineering and Science 21 (1981), S. 151-154 
    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: Recovery experiments above Tg have been performed on glass bead and short glass fiber polystyrene composite sheets obtained from extrusion and subsequent hot drawing. A shift procedure has been applied to recoil data using the Williams-Landel-Ferry (WLF) equation with the same values of C1 and C2 used for unfilled polystyrene. The data reported show that an improvement of the dimensional stability of a drawn thermoplastic material can be obtained by adding very low volume percentage of fibers. Moreover, all the recoil data have been reduced to a unique generalized master curve which takes into account the draw ratio, the filler content, and geometry, using a fractional distance from equilibrium as a measure of the recovery. These results indicate that the presence of the filler does not affect the recoil kinetics of the polymeric matrix.
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  • 48
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Gel Permeation chromatography (GPC) yielded high values for branching frequency. Low polymers persisting long into the reaction and impurities resulted in almost constant number average molecular weights and steeply rising polydispersity. The percent insolubles was low and passed through a maximum attributed to a 1,2,3-propantriol/isocyanate reaction product which was insoluble and became solubilized by the addition of polybutadiene. The dynamic viscosities of the products rose with conversion. When studied over various shear rates, the curves could be extrapolated to zero shear values. The relationship between zero shear viscosity and molecular weight yielded a slope of 3.5 for linear samples and a lightly branched sample prepared using 1,6-hexamethylene diisocyanate. The lightly branched samples made using 2,4-toluene diisocyanate yielded slopes less than 3.5. The highly branched samples yielded slopes well above 3.5. The moduli increased rapidly with reaction time and then levelled off. In the absence of 1,2,3-propantriol, the loss modulus surpassed the storage modulus. When 1,2,3-propantriol was added, the moduli increased more rapidly, levelled off at higher values, and the storage modulus exceeded the loss modulus. Studies of the swelling of the final product showed that these measurements yielded abnormally high values for the molecular weight between crosslinks; evidence of poor network formation.
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  • 49
    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: Cold working (rolling) of polycarbonates introduces residual stresses and molecular orientation both of which can improve, the notched Izod impact value. Annealing relieves both residual stresses and orientation. Annealing for various time periods established the critical level of residual stress necessary for the ductile failure mode of polycarbonate in the Izod impact test. The relaxation of both residual stress and molecular orientation was measured as a function of annealing temperature, for annealing times of 2 hs, and the relative changes have thus been determined. It is shown that residual stresses cannot be entirely removed without significantly influencing orientation for 2 h annealing times.
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  • 50
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    Polymer Engineering and Science 21 (1981), S. 145-150 
    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: Three aspects of the failure of thermoplastics, having a special importance in engineering, are investigated. They are: (a) Transition from linear to nonlinear viscoelasticity; (b) Crazing; (c) Fracture. Energy related criteria, developed from the Reiner-Weissenberg thermodynamical theory of strength, are used for the characterization and prediction of failure under its different forms, for simple uniaxial loading histories such as creep, stress relaxation and constant rate of strain. The computation of the stored and dissipated parts of the specific stress energy becomes possible in a relatively simple way, if the relaxation modulus and the creep compliance are approximated by Prony-Dirichlet-type series with a finite number of terms. Published experimental data, as well as experiments carried out by the author on different thermoplastics are in very good agreement with theoretical results. Further, based on experimental data, the equations obtained can be reduced to very simple and useful relations. The influence of elevated temperatures (below the glassy-transition point) on failure is also considered.
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    Polymer Engineering and Science 21 (1981) 
    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
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  • 52
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    Polymer Engineering and Science 21 (1981), S. 163-171 
    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 series of segmented polyurethanes based on hydroxylterminated polybutadienes (HTPBD) and their hydrogenated derivatives (HYPBD) has been synthesized. Thermal, mechanical, and spectroscopic studies were carried out over a wide temperature range to elucidate the structure-property relationships existing in these polymers. Both thermal and dynamic mechanical response showed a soft segment Tg at -74°C for the unsaturated polyurethanes and at -69°C for the hydrogenated samples. In addition, two hard segment transitions are observed by differential scanning calorimetry (DSC) at 40 and 75°C and a softening region by thermal mechanical analysis (TMA) at 190°C. The low Tg, very close to that of the free HTPBD and HYPBD and independent of hard segment content, indicated that these polymers were well phase separated. Results of infrared analysis revealed that at room temperature, 90-95 percent of the urethane N-H groups formed hydrogen bonds. Since hydrogen bonding resides only within the hard segment domain in these butadiene-containing polyurethanes the extent of H-bonding served as additional evidence for nearly complete phase segregation. From dynamic mechanical studies, the plateau modulus above the soft segment Tg and stress-strain behavior depended upon the concentration of hard segments. A slight increase in the modulus, a moderate increase in stress (σb), and decrease in elongation accompanied a higher hard segment content. The thermal and mechanical response of these polyurethanes appears to be consistent with behavior observed for other phase segregated systems. Variations in behavior resulting from hydrogenation of the precursor prepolymer are discussed.
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    Polymer Engineering and Science 21 (1981), S. 172-181 
    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 shown that the annealing of a high molecular weight, high density polyethylene at different temperatures ranging from 393.2 to 405.2 K influences the density of the material, the lamellar structure as studied by differential scanning calorimetry and transmission electron microscopy, and the necking and fracture behavior at constant uniaxial tensile loading in air at 313 K. In previous reports, a marked transition in the necking and fracture behavior of high density, high molecular weight polyethylene under constant uniaxial tensile loading has been reported. The nominal stress and the maximum strain rate of this transition show minima for polyethylenes annealed at temperatures of about 401 K. By combining these data with data for the lamellar structure a hypothesis that explains the necking/fracture behavior is set up. The heat treatment at temperatures from 393.2 to 403.2 K of the original non-equilibrium lamellar structure causes a molecular fractionation preferentially of low molecular weight and branched material. These segregated parts may then act as fracture initiators and thus lower the resistance towards fracture. Other structural effects such as those proposed by McCready and co-workers may also be of importance. The fracture curves at nominal stresses below transition of the materials annealed at 396.7 and 401.2 K for 24 h are shifted to shorter times in comparison with that of the non-annealed material and this can also be explained by molecular fractionation. The time to necking at 14 MPa nominal stress seems to be related to the lamellar thickness of the samples.
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  • 54
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    Polymer Engineering and Science 21 (1981), S. 185-188 
    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: Poly(vinyl chloride) and chlorinated poly(vinyl chloride) films were saturated at 100°C with fluorotrichloromethane (Genetron-11, a foaming agent) and then allowed to desorb at RT and 65°C. The desorption data for a three month period was fitted into a mathematical relationship which could be used for long term predictions of the G-11 retention in the films. Using thermoanalytical techniques, plots of glass transition temperature vs G-11 concentration were made for the polymers under study. These plots were used to demonstrate the effect of stabilizer, polymer type and temperature on the desorption of the G-11.
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  • 55
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    Polymer Engineering and Science 21 (1981), S. 189-195 
    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: Uni- and biaxial stretching of poly(ethylene terephthalate) (PET) specimens of appropriate geometry at temperatures near the glass-rubber transition may lead to non-uniform deformation unless the draw ratio exceeds a critical value, the natural draw ratio, characteristic of the onset of strain hardening due to stress-induced crystallization. Experimental results obtained in the present investigation show that natural draw ratios in uni- and biaxial stretching decrease with increasing resin molecular weight and with decreasing temperature. Undesirable uneven wall thickness distribution in biaxially stretched cylindrical parisons can only be prevented if draw ratios in both orthogonal principal stretching directions exceed the corresponding natural values. The minimum thickness reduction required for uniform biaxial stretching of a cylindrical parison at 95°C may vary between 12 and 5 depending on the resin's molecular weight or viscosity and this will affect the optimum design of parison geometry. The degree of unbalanced biaxial molecular orientation in the wall of cylindrical parisons stretched up to or beyond the natural draw ratios also depends on the resin molecular weight. Unbalanced biaxial orientation has been investigated by means of wide angle X-ray diffraction and birefringence measurements as well as its effect on various properties: rigidity, yield stress, creep compliance, and dimensional stability.
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  • 56
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    Polymer Engineering and Science 21 (1981), S. 205-211 
    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 impact modification mechanisms of polycarbonate (PC) blended with polyethylene (PE) and blends of polyxylenol ether (PXE)/high impact polystyrene (HIPS), were studied using a volume dilation technique. With two extensometers, measurements of volume change during tensile deformation were made on the plastics. Strain rates of 2 × 10-5 s-1 to 4 s-1 were achieved with a MTS servo-hydraulic testing machine. Analysis of both systems were supported with scanning and transmission electron microscopy. Results on the PC/PE system indicate that the impact modification mechanism is one of voiding and shear banding. The mechanism appeared to be rate sensitive: the amount of voiding increased with rate. The toughening mechanism in the PXE/HIPS blends is identified as a combination of crazing and shear banding. The amount of shear banding that occurs is proportional to the amount of PXE in the blends. The point of craze initiation was found to be delayed by increasing strain rate. The stress for craze initiation appears to be greater than for shear banding.
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  • 57
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    Polymer Engineering and Science 21 (1981), S. 196-204 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An experimental study was carried out to investigate the effects of coupling agents on the rheological properties, processability, and mechanical properties of highly filed polypropylenes (PP). Inorganic fillers used were CaCO3 and glass beads, and coupling agents used were two silane coupling agents, N-octyl triethoxy silane and γ-aminopropyl triethoxy silane, and one titanate coupling agent, isopropyl triisostearoyl titanate. It was found that the addition of the coupling agents to the PP-CaCO3 (50 wt percent) decreased the melt viscosity and increased the melt elasticity (first normal stress difference). However, the addition of the silane coupling agents to the PP-glass beads (50 wt percent) affected the rheological properties of the melts quite differently. The N-octyl triethoxy silane had relatively little effect on either the melt viscosity or the melt elasticity, whereas the γ-aminopropyl triethoxy silane increased the melt viscosity and decreased the melt elasticity. The CaCO3- or glass bead-filled polypropylenes, with and without coupling agents, were injection-molded and the mechanical properties of the molded specimens were measured by the use of an Instron testing machine. It was found that the effect on the tensile strength and percent elongation of the filled polypropylenes depended upon the specific coupling agent utilized. A melt-spinning study was also carried out to investigate the effect of coupling agents on the spinnability (defined as the maximum draw-down ratio) of the PP-CaCO3 system, and on the mechanical properties of the melt-spun fibers. It was found that the spinnability of the PP-CaCO3 was enhanced considerably by the addition of the coupling agents, and that the tensile strength of the melt-spun fibers was also improved by their addition. Scanning electron micrographs were taken of the fracture surface of injection-molded specimens and an attempt was made, with the aid of photomicrographs, to explain the mechanical properties of molded specimens observed experimentally.
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  • 58
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    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 dependence of crack propagation energy R of an acrylonitrile-butadiene-styrene (ABS) resin on crack velocity was characterized in air and in several organic liquids. In the liquids an abrupt transition in R from a level like that in air down to a level characteristic of the liquid occurred with decreasing crack velocity. The velocity at the transition varied strongly with liquid viscosity. A simple model of each craze at the crack tip as a set of pipes through which liquid flows, driven by capillary force and retarded by viscous drag, serves to predict the transition velocity.
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  • 59
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    Polymer Engineering and Science 21 (1981), S. 223-226 
    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: Following the reported pronounced effects of metal halides incorporated into nylon-6 on its glass transition temperature, melting temperature, melt viscosity, crystallization rate and final crystallinity, the tensile mechanical properties and crystallinity of nylon-6 as affected by the absorption of metal halides were studied. At low salt content, some of the mechanical properties are substantially altered and at higher salt concentrations the ductile polymer becomes brittle. There is no marked difference between the salts studied (CuCl2, CuBr2, FeCl3) regarding their effects on the polymer mechanical properties. In the concentration range studied, absorbed Cu salts do not significantly change the polymer's degree of crystallinity, whereas absorbed FeCl3 results in a pronounced reduction, indicating its effect also on the crystalline phase.
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    Polymer Engineering and Science 21 (1981), S. 212-217 
    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: Simple quantitative mixing experiments in well-defined deformations clearly demonstrate the validity of previously derived equations relating deformation and mixing. A simple mixture of black and white polyethylene is studied by direct measure of striation thickness. The well-known linear relationship in simple shear is demonstrated. By using a simple method for uniform reorientation, the second power relationship in shear once interrupted, the third power relationship in shear twice interrupted and the fourth power relationship in shear interrupted three times are demonstrated. In uniaxial elongational mixing of a silicone fluid, exponential dependence of mixing on strain is demonstrated.
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    Polymer Engineering and Science 21 (1981), S. 248-248 
    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
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  • 62
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    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 biaxial stretching plays a central role in several polymer processes, there has been no technique suitable for laboratory study of controlled biaxial stretching of molten thermoplastics at typical melt processing temperatures. The sheet inflation technique, which has been used previously to study rubbers and very high viscosity melts, has been adapted for use with molten thermoplastics by the use of oil as an inflation medium. Problems encountered in the use of the first prototype were eliminated in a second model, which is thought to produce reliable results. Stress growth data are presented for a low density polyethylene and for a polystyrene. A basic limitation of the technique is that the maximum achievable strain is in the range of 1.3 to 1.7, and this is often insufficient to bring out the nonlinear viscoelastic behavior of the melt.
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    Polymer Engineering and Science 21 (1981) 
    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
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    Polymer Engineering and Science 21 (1981), S. 381-384 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of saturated aliphatic fatty acids and a number of fluorinated polar organic compounds on the release of polyurethane foam from cold rolled steel has been investigated. Little release was observed with aliphatic acids of less than 10 carbons or with the organic compounds. Release behavior increased with aliphatic chain length from C12 to C18. Stearic acid release increased only marginally above 0.034 μ g/cm2. Infrared studies of demolded eluted surfaces indicated that stcaric acid at levels of up to 178 μ g/cm2 was apparently removed from the surface by foam.
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  • 65
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    Polymer Engineering and Science 21 (1981), S. 385-389 
    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 polymeric materials, polyphenylene oxide, polyquinoline, acetylene substituted polyimide, and polybenzimidazole, reported to possess high-temperature resistance, were investigated in order. to determine their outgassing characteristics as related to their suitability for high temperature applications in confined structures. The materials were sequentially exposed to 150, 250 and 450°C for 3 h periods and the types and amounts of their outgassed products were determined. The amounts of outgassed- products were small from polyquinoline, acetylene substituted polyimide, and polybenzimidazole. It was concluded that those materials would be suitable for use in applications where high-temperature resistance (up to 450°C) is required, providing that normal ventilation is available. The quantity of outgassed products from polyphenylene oxide was too great to consider that material suitable for shipboard or other confined structure applications requiring high-temperature resistance.
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  • 66
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    Polymer Engineering and Science 21 (1981), S. 398-405 
    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 cold press workability of aluminum-polyethylene sandwich laminates is experimentally investigated by a deep drawing process with a conical die. “Planium” of 2 mm thickness, in which the core layer, high density polyethylene, is sandwich-laminated between two aluminum sheets, is used as a test specimen. Soybean oil is employed as a lubricant. The dimensions of the drawing die set are determined for a circular, blank so that the tensile fracture of the drawn.cup occurs at the top corner of the punch. The limiting draw ratio (LDR) is experimentally explored by using many blanks of various initial diameters. In general the maximum punch load in successful drawing increases linearly with increasing draw ratio. Because of the sandwich structure, the fracture of the drawn cup occurs twice. The initial fracture (LDRs) corresponds to a fine bending fracture at the aluminum surface. The second fracture (LDRB) is the complete fracture of the whole laminate. The effect of punch corner radius, working velocity and thickness fraction of aluminum and polyethylene on LDRS and LDRB are studied. The strain distributions of deep drawn cup in three orthogonal directions are analyzed experimentally.
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  • 67
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    Polymer Engineering and Science 21 (1981), S. 415-423 
    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 main objective of the work is to explore the problem of producing polymers of any desired molecular weight distribution (MWD) in isothermal, solution, “living”, anionic polymerizations carried out in continuous tubular reactors. For this purpose, a novel control scheme was designed and implemented, which involves the periodic operation, of the monomer solution flow rate, with the flow profile automatically derived from the required MWD and other data. For experimental validation, a polymerization rig was especially built that included a process computer and an automatic gel permeation chromatograph. The chromatograph permitted the measurement of the MWD of the reactor effluent in a matter of minutes and the process computer was employed to implement the control policies and to perform the chromatograph data acquisition and reduction. In spite of the practical problems encountered, experiments showed at least a semi-quantitative validity of the method.
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  • 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: Torsion Impregnated Cloth Analysis (TICA) uses fiber glass cloth as support for polymeric resins and measures the clothresin composite's in-phase and out-of-phase dynamic mechanical responses with a Rheometrics mechanical spectrometer. The TICA thermoscan results of a thermoplastic were compared with that of the neat material. A similar comparison was made between the isothermal curing results of a thermosetting resin and the corresponding parallel plate and TBA measurements. The peaks associated with the vitrification were verified to correspond to those in the glass transition region. Conventional thermoscans of partially cured specimens with known Tg were shown under certain conditions to give erroneous results about the glass transition temperatures. A reduced parameter (T-Tg) was introduced to describe the response of a specimen undergoing additional cure while being subjected to a thermoscan. Examples using this parameter to understand seemingly complex experimental results are given.
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  • 69
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    Polymer Engineering and Science 21 (1981), S. 406-414 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of compositional variables on the mechanical properties of a UV-cured coating was investigated. The coating contains two monomers, 2-ethoxyethoxyethylacrylate (EEEA) and N-vinyl-pyrrolidone (NVP), and a higher molecular weight resin (MW ∼1000) which is a commercial urethane diacrylate. In addition, a photoinitiator, 2,2-dimethoxy-2-phenylacetophenone, was present at a constant concentration. It was found that the mechanical properties of the cured films depend mainly on the concentration of 2-ethoxyethoxyethylacrylate (EEEA). Spectroscopic analysis. showed that EEEA undergoes both homopolymerization as well as an addition reaction with the photoinitiator and is thus not incorporated in the crosslinked matrix but rather acts similar to a compatible plasticizer. Kinetic analysis of the reactions of the single components and mixtures showed widely diverging reactivities of the components with homopolymerization of EEEA being a favored reaction path. A speculative conclusion is that, to avoid homopolymerization and monomeric reactions, optimized coating formulations (coatings with mechanical properties that are not affected by small compositional variations) should be based on monomers and oligomers with similar reactivities.
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    Polymer Engineering and Science 21 (1981), S. 424-432 
    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 of a polymerizing fluid between rotating concentric cylinders has been analyzed theoretically. A solution has been obtained employing a finite difference method. Using a RIMtype (reaction injection molding) urethane system as an example, the velocity, temperature, and NCO group concentration fields have been described as functions of time. A numerical example is given to demonstrate the applicability of the present analysis to reactive processing and viscometry. The mixing characteristics and the flow rate associated with circular drag flows involved, e.g., in reactive extrusion, have been shown to depend strongly on the operating conditions. It has also been demonstrated that the range of applicability of Couette viscometers to fast curing systems may be limited by the interfering time-dependent temperature gradients involved. It has been concluded that analysis of the. present nature provides a useful design and evaluation tool applicable to Couette flow problems in reactive processing and viscometry.
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    Polymer Engineering and Science 21 (1981) 
    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
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  • 72
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    Polymer Engineering and Science 21 (1981), S. 433-438 
    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: Variously dispersed two-component blends of linear polyethylene and a thermoplastic rubber were subjected to different thermal histories after compression molding and their properties were evaluated. It has been shown that ultimate properties of the blends are not defined by the composition, but vary greatly with degree of dispersion and thermal history. Stronger materials failing in a ductile manner were produced under shock cool conditions and in, finely-dispersed blends. Brittle failures and weaker materials were favored by annealing procedures and in blends subjected to brief and/or lowshear dispersion procedures. Time and temperature dependent changes in properties of blends prepared under standard conditions have been observed and activation energies for the aging process calculated. Data interpretation was based on a hypothesis of domain morphology in the blends, and on the existence of “tie molecules” which help to determine the cohesive strength of domain boundaries.
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    Polymer Engineering and Science 21 (1981), S. 441-448 
    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: Thermomechanical analysis was carried out for various phthalocyanine resins. The polymer based on the C-10 diamide resin was then chosen for evaluation as a potential composite matrix material. Prepregs with Thornel 300 graphite reinforcements were successfully prepared using a hot-melt technique. The processability of this material was studied by employing instrumental techniques including differential scanning calorimetry, thermal gravimetric analysis and dynamic dielectric analysis. A cure cycle was developed for the fabrication of angle-ply laminate using the conventional vacuum-bag technique in a hydraulic press. Laminate mechanical properties both in tension and in flexure were determined. The results for the C-10/T-300 samples were shown to be similar to those of an epoxy/graphite and a polyimide/graphite composite system.
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    Polymer Engineering and Science 21 (1981), S. 449-456 
    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 technology of using glass fibers to increase the modulus and the strength of polymeric systems is well-developed. Much less widely exploited has been the enhancement of properties by orienting the molecules of the polymer itself. The purpose here was to look for a synergistic combination of these two strategies: using glass fiber-filled polystyrene and introducing molecular orientation into the polystyrene matrix. For rheological reasons it is not possible to introduce large stretch ratios in the rubbery state and thus the amount of molecular orientation that can be frozen into the quenched glassy composite is small. Even so, however, the rubbery elongation (which we associate with subsequent molecular orientation) has a very significant effect on the final (room temperature) mechanical properties. Analysis of these properties was made in terms of various theoretical models (those of Brody and Ward, Smallwood-Guth, and Russel and Acrivos for the Young's modulus; and that of Kelly and Tyson, as modified by Lees, for the tensile strength). These comparisons showed that the brittleness of unoriented polystyrene is such that the matrix does not effectively distribute the stress along the length of the fiber and thus the benefit of the length is not realized; whereas the higher ductility of oriented polystyrene allows such transfer and a consequent improvement of properties.
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    Polymer Engineering and Science 21 (1981), S. 461-466 
    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 interlaminar shear fatigue behavior of the sheet molding compound SMC-R50 has been studied. A thick-laminate, short beam shear test was employed to characterize S-N behavior for the material at 21 and 90°C. The shear modulus (Gxy) was determined at 21 and 90°C and the effect of fatigue on modulus at both test temperatures is discussed. Scanning electron microscope (SEM) and optical photomicrographs of pristine and post test specimens were studied to assess the relationship between material microstructure and the observed fatigue results for strength and modulus. The experimental evidence suggests that the fatigue life for this material is determined by a single flaw growth mechanism, rather than a global “wear out” process.
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    Polymer Engineering and Science 21 (1981), S. 457-460 
    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 heat transfer data recently presented by Migliaresi, et al. are used as the basis for developing two models of the coupled heat transfer-phase transition phenomena in polymeric composites containing thermally active fillers. Both models represent an extension to heat transfer of ideas which have originated in the analysis of mass transfer phenomena in polymeric materials. The second model is able to correlate all the available data within 0.5°C.
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    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: All measures of impact resistance have shortcomings. The ASTM tests, Izod, Charpy, and drop-dart, measure impact at a single velocity. Furthermore, the Izod and Charpy tests impose an unrealistic unidimensional stress on the test specimen. Indirect gauges of impact toughness, such as the area under the tensile stress-strain curve (tensile work), flexural modulus, or resin cracking in mandrel bend tests, are normally conducted at unrealistically low straining rates. Variable-rate impact testers have been developed to overcome these shortcomings. In this paper, results obtained from a variable-rate tester are compared with those from other methods for assessing composite toughness. Data are reported for flexible and brittle low profile press molding resins, tested as SMC (sheet molding compound) moldings by Izod, drop-dart and variable-rate impact. Indirect measures of impact resistance, mandrel bend and flexural modulus, are also discussed. The effects of resin flexibility and the composite glass content are demonstrated. The glass content affects the ultimate failure strength of the composite but not the failure of the resin matrix. The resin flexibility affects the initial stages of failure.
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  • 78
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    Polymer Engineering and Science 21 (1981), S. 474-482 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of moisture on the curing reaction of Hercules 3501-6/AS graphite-epoxy prepreg was investigated. Test samples of prepreg were aged under humid conditions, while control samples were aged under identical temperature conditions but with negligible humidity. Determinations of the amounts of moisture absorbed and desorbed fom the samples were accomplished gravimetrically. Dielectric analysis was used to monitor the relative reaction rates and overall activation energies of the prepreg after various aging periods. Changes taking place in monomer concentrations were observed using high performance liquid chromatography (HPLC). As aging continued, samples aged under humid conditions displayed, significant decrease in the overall activation energy accompanied by increased reaction rates. This change did not occur in the control samples. Samples aged in high humidity showed increased conversion of monomers to polymer when compared to dry aged samples. The aging time required before the above changes became apparent was temperature dependent; the higher the aging temperature, the sooner the changes in reactivity occurred.
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  • 79
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    Polymer Engineering and Science 21 (1981), S. 483-492 
    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 recently developed kinetic model has been applied here to describe the polyester-styrene addition copolymerization. By assuming that the termination step is negligible and the reaction rate between inhibitor and initiator free radical is much, faster than any other reactions, the kinetic mechanism can be simplified to be expressed as a single equation. The parameters, rate constant of initiator decomposition and rate constant of propagation, are estimated from the induction time and the time to the peak exotherm of isothermal differential scanning calorimetry (DSC) curves. Temperature profiles inside plate sections of SMC parts during molding are predicted by a mathematical model in which addition polymerization is coupled with heat transfer. The predicted temperature profiles compare well with the experimental results. The model is also used to predict the cure time of different part thicknesses, mold temperature and initiator concentration. Glass fibers playa role as a heat sink as well as heat conductor during curing. Adding glass fibers to SMC not only lowered the maximum exotherm but also reduced the cure time.
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  • 80
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    Polymer Engineering and Science 21 (1981), S. 507-509 
    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 development of polymer/concrete composites is directed at both improved and new construction materials by combining the ancient technology of hydraulic-cement-concrete with the modern technology of polymers. The need for such materials has always existed since the traditional construction material portland-cement-concrete (PCC) suffers the drawbacks 4 little or no resistance to chemical attack; rapid deterioration under freeze/thaw conditions due to cyclic temperature changes; low tensile, shear and bond strengths; and inherent micro-structural menaces (voids, shrinkage-cracks, capillaries) which, individually or in combination with each other, shorten the service life of the structures.
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  • 81
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    Polymer Engineering and Science 21 (1981), S. 509-509 
    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
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  • 82
    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: Samples of a filled elastomeric ablative material were stored at 45°C and ca. 10-6 torr for 7 months. Their tensile stressrelaxation modulus at constant strain was measured throughout the 7 months. Results of the testing are discussed primarily by comparisons of the data to atmospheric-pressure moduli (determined in this work for shorter periods of time) and with moduli predicted from short-time testing. Confirmation of the strengthening effects of vacuum on this composite were obtained. The use of time-temperature superposition techniques as an approximate accelerated testing procedure for this material under these conditions was also verified.
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  • 83
    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 capillary rheometer has been designed and built which is capable of making measurements in the shear rate range: 100 s-1 〈 \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document} 〈 3 × 106 s-1. The rheometer uses the injection unit of an injection molding machine. A modification of this rheometer has been built which consists of two dies in series. Both dies may be used for rheometric purposes, but the second die is intended primarily to act as a valve to allow the mean pressure to be varied in the first die, while keeping the pressure drop constant. In this way the pressure dependence of viscosity may be measured in the injection molding shear rate range. Measurements have been made on unfilled and short glass fiberreinforced polypropylene melts and flow curves covering seven decades of shear rate are presented for the unfilled material. The temperature of the extrudate may be as much as 70°C higher than the barrel temperature. Two effects, shear heating and compression heating, contribute towards this temperature rise, and calculations of the extrudate temperature are in good agreement with measured values. At high shear rates the viscosity is affected by the pressure needed to drive the flow. The effect of pressure on the viscosity outweighs the effect of temperature on the viscosity at high shear rates. A value for the pressure coefficient of viscosity of unfilled polypropylene β = 0.0058 m2 MN-1 has been obtained.
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  • 84
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    Polymer Engineering and Science 21 (1981), S. 745-747 
    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: Glassy crosslinked networks were prepared by copolymerization of methyl methacrylate with up to 5.2 mole-percent of ethylene and triethylene dimethacrylates. The moduli of these materials were measured by tensile and two dynamics methods: forced resonance vibration and ultrasonic. Impact strength were measured using the Izod geometry and Sharpy notched samples to induce brittle fracture. The increase in the length of the crosslinking agent caused an increse in the deformability and impact strength of these materials without any effects in the moduli.
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  • 85
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    Polymer Engineering and Science 21 (1981), S. 776-781 
    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 microstructural changes in isotactic polypropylene (PP), subsequent to quench from the melt to around Tg were studied using dynamic mechanical loss, volume dilatometry, small and wide angle X-ray scattering, infrared and NMR spectroscopy. The β-transition loss tangent and the specific volume decreased linearly with logarithm of aging time. Dynamic mechanical loss and NMR spectroscopy results established that amorphous chain mobility reduced during aging. X-ray and IR techniques showed that the crystallinity, the crystalline density, and the average chain conformation do not change during aging. Tensile tests indicated that diffusion of air or moisture into the polymer is not a competitive mechanism for the aging phenomenon. A simple free-volume model is quantitatively consistent with these observations. The fraction of the material which cannot age increased as the quench temperature decreased. Further, at lower temperatures a portion of the nonageable fraction is shown to reside in the amorphous fraction.
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  • 86
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    Polymer Engineering and Science 21 (1981), S. 873-873 
    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
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  • 87
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    Polymer Engineering and Science 21 (1981), S. 922-924 
    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: Volume relaxation of glassy polymers has been followed by diffusion of simple alkane permeants. The changes in diffusion rates allow direct monitoring of changes in segmental mobilities of the polymers. In general, the diffusion rates decrease linearly with annealing time on double-logarithmic plots and then level off as equilibrium is reached. The reduction in diffusion rates, however, can be recovered by raising the temperature above the glass transition temperature and then cooling to the same annealing temperature. Such behavior indicates that the predominant molecular process responsible for changes in mechanical properties of glassy polymers that accompany volume relaxation is not “structure formation” but is the loss of segmental mobilities arising from a reduction of the total free volume in the polymers.
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  • 88
    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 conformational and enthalpic changes that occur in poly(vinyl chloride) (PVC) glasses that have been vitrified from the melt under pressure have been examined by Fourier transform infrared spectroscopy and quantitative differential scanning calorimetry. It is shown that these pressures freeze in the high energy states that are characteristic of the vitrification temperature and increase the apparent glass transition temperature of the polymer. In addition, pressures in excess of the vitrification pressure, cause intermolecular effects that can be relaxed out below Tg. Both of these processes create characteristic endothermic and exothermic changes in the apparent heat capacity of the glass that appear over a period of time and are sensitive functions of the glass formation. processes as well as the subsequent annealing history. The endothermic events are interpreted as the stress perturbed volumetric relaxation process while the exotherms are associated with the release of the frozen in stresses.
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  • 89
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    Polymer Engineering and Science 21 (1981), S. 930-935 
    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 water absorbed by poly(vinyl acetate), PVAc, at 23°C was found in two states. The first, which can account for up to 4 weight percent, was bound to the polymer. The second was in a freezable or clustered form. The latter type of water had no effect on PVAc's glass temperature, whereas, the former kind plasticized Tg. In annealing studies, the enthalpic and dielectric response of PVAc when held at a fixed temperature increment, ΔT, below Tg, was observed to be independent of the amount of bound water. The time dependence of the shift in the dielectric relaxation spectrum and the recovery of the enthalpy towards its equilibrium value as PVAc approached its equilibrium glassy state from a lower temperature as compared to a higher temperature was initially slower. This delayed response to expansion was of the order of the polymer's average relaxation time at the lower temperature. A model was proposed to explain this asymmetric behavior based upon changes in the polymer's free volume as well as its occupied volume.
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  • 90
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    Polymer Engineering and Science 21 (1981), S. 951-957 
    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: Observations of time dependent behaviors of polymeric systems are often made with the assumption that the glass transition temperature will remain constant during the course of the experiment. This assumption may not be valid for partially cured thermosetting system, where additional cure can increase the glass transition temperature. The observed behavior can be expressed as a time derivative function of two independent variables, the experimental temperature and the state of the system. With proper assumptions, these two variables can be reduced to a single parameter (T - Tg), whose time derivative will give terms representing the temperature and curing effect separately. Dynamic mechanical measurements have been made on partially cured systems, and the effects of the additional cure on the observed properties are observed. The seemingly complex experimental observations can be qualitatively interpreted with the change of the parameter (T - Tg).
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  • 91
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    Polymer Engineering and Science 21 (1981), S. 958-964 
    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: Application of the fundamental variational principle of nonequilibrium thermodynamics has permitted recognition that all polymer solidification including glass formation occurs by a dissipative process which results in an inhomogeneous dissipative structure rather than an equilibrium structure. Although an equilibrium structure must he homogeneous and time independent, the definition of both homogeneity and time independence depends upon the scale and precision of the measurement of time and distance. Thus, whether one considers a glass to be a homogeneous equilibrium structure or an inhomogeneous nonequilibrium structure, depends upon the scale and precision of measurement. However, progress in understanding the molecular arrangement in glass can only come by considering a glass as an inhomogeneous dissipative structure.
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  • 92
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    Polymer Engineering and Science 21 (1981), S. 970-977 
    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: Craze healing was observed in many amorphous glassy polymers. A detailed study of the kinetics of craze healing in atactic polystyrene (Mw = 255,000) was conducted. The crazes were created in 0.08 mm films in air at room temperature, To, and constant stress, σo ⋍ 2,300 psi, healed at temperature Th for a time, Th, at σ = 0, and recrazed at To and σo. Nucleation times, τ1 and τ2, and growth rates, L1, and L2, for the first and second loading, respectively, were measured as a function of th and Th for individual crazes using dark field optical microscopy. Complete optical and mechanical healing was observed for Th ≥ 70°C(Tg ≅ 100°C). At constant Th, healing progressed in five stages with increasing th as follows; (i) no healing, τ2 = 0, L2 ≫ L1; (ii) partial healing, τ2 〈τ1, L2 〉 L1; (iii) similar growth, τ2 = τ1, L2 = L1; (iv) slower growth, τ2 〉 τ1, L2 〈 L1; (v) disappearance, τ2 → ∞, L2 → 0. A craze healing envelope of Th vs Th was obtained for the above stages. Craze healing occurred by line mode in which uniform healing occurred along the entire length of the craze.
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  • 93
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    Polymer Engineering and Science 6 (1966) 
    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
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  • 94
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    Polymer Engineering and Science 6 (1966), S. 79-82 
    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 determination of the state of resin advancement in asbestos-phenolic prepregs is important to the processor of this material. Many tests have been proposed for measuring this condition. In this article the follwing tests were made on the prepreg and resin extracted from the prepreg to measure advancement: viscosity, Chang Index,-infrared absorption dielectric constant, dissipation, dielectric constant, and dissipation factor, volume resistivity, and tear strength. Infrared absorption, dielectric constant, and dissipation factor correlated best and were the most sensitive indicators of resin advancement.
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  • 95
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    Polymer Engineering and Science 6 (1966), S. 94-96 
    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
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  • 96
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    Polymer Engineering and Science 6 (1966), S. 124-127 
    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: Color development in outdoor applications has been widely used as an indication of breakdown in plastic materials although this does not always indicate a change in physical properties. Appearance factors are easily and precisely evaluated by measuring color and surface changes. Measurement of physical property changes is more comples and more meaningful. An optimum test method should measure a property with time, environment and sample form. Ideally, the data should determine service life. The test specimen should be adaptable to a variety of samples. Of the many physical tests of weatherability, impact strength appears most interesting. An inexpensive Variable Impact Tester was Modified and Developed for Measuring the effect of aging on rigid PVC. Data are presented showing the relation between impact values and temperature, sample thickness, process conditions and various environmental exposures.
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  • 97
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    Polymer Engineering and Science 6 (1966), S. 135-141 
    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 coefficients of friction of solid polyolefins against metal surfaces has been determined as functions of pressure, temperature, and metal surface finish. The polymers studied were a low debsity (branched) polyethylene, a high density copolymer, and a high density (linear) polyethylene homocopolymer, and a high density (linear) polyethylene homopolymer. Four metal surfaces were used, with surface roughnesses ranging from 1 1/2 to 18 microinches. The pressure and temperature ranges were 0 to 355 psig and 72 to 225°F, respectively. Data were obtained for the polymers in two forms: granules and flat smooth dise, except for the high density homopolymer which was tested in the disc from only. In general, the results indicated that, for all granules, the coefficient was essentially independent of pressure, but decreased with increasing temperature until the melting point was reached; it varied with metal surface roughness which was greatest for the low density polymer. For the smooth surfaced disc samples, the coefficient also decreased with increasing pressure with high values at low pressure indicating strong adhesion between the polymer and metal surfaces.
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  • 98
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    Polymer Engineering and Science 6 (1966), S. 156-157 
    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: To determine the optimum conditions for vacuum forming quality parts, a precise method of determining internal stress required development. The approach investigated was based on the shrinkage of a heated stressed part. Small stress should be proportioned to strain. By exposing loaded tensile specimens simultaneously with the formed part, the material modulus is determined. Results indicated creep which was minimized by using the correct modulus to calculate internal stress. Stresses in a normally formed part and in a part formed cool were compared at two temperatures. Values were higher in most areas of the cool-formed part and consistent at the two temperatures. This method probably can be used on other materials and possibly on injection molded parts.
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    Polymer Engineering and Science 6 (1966), S. 176-180 
    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: Bulk compressibilities of a series of linear and crosslinked polymers have been measured, in a Matsuoka-Maxwell apparatus, at pressures up to 10,000 atmospheres and at temperatures to 202°C. These polymers exhibited nonlinear compressibility characteristics and a maximium compressibility of about 15% at 10,000 atmospheres. At slow loading rates, data were obtained for the amorphous polymers which could be expressed as glass-rubber phase gisgrams. The nature of the observed compressibilities are discussed and the usefulness of the data is indicated.
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    Polymer Engineering and Science 6 (1966), S. 231-239 
    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: Antioxidants and UV absorbers are vital to the commercialization of polypropylene because of their influence on this polymer's light stability, heat or oxidative stability, processing stability, and gas fading due to nitrogen oxides. The effects of these stabilizers are measured in terms of polypropylene's initial color, color retention, and retention of physical properties when the polymer is exposed to direct weathering and to elevated temperatures. The relative washfastness or resistance to extraction by aqueous systems under various laundering conditions is another important, measurable property of UV absorbers and antioxidants in polypropylene. Such measurements are usually made using stabilized polypropylene molded plaques and monofilaments containing UV absorbers, antioxidants and, often, combinations of the two.
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