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  • Articles  (1,172)
  • Chemical Engineering  (1,172)
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  • Wiley-Blackwell  (1,172)
  • 1985-1989  (1,172)
  • Physics  (1,172)
  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    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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  • 2
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1-1 
    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
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  • 3
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 2-12 
    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 aging and lifetimes of polymeric materials depend on the reaction of these materials to the particular stresses which are applied. In many cases the molecular weight of the polymer is changed and this affords a way to follow aging phenomena. In the simplest case a homopolymer is subjected to a stress which increases or decreases its molecular weight without any chemical changes. As the situation becomes more complicated, changes in chemical composition occur and different sized molecular species are generated. These new species may be of extremely low molecular weight or they may be in the form of crosslinked gel. This paper reviews methods which are available for the determination of molecular weight and molecular weight distribution of polymeric materials. Recently developed or modified techniques are treated in more detail. Techniques which may be used to characterize the oligomer region or analyze for the presence of crosslinked gel are included.
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  • 4
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 13-18 
    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 provides a summary of four EPRI-sponsored contracts that studied the physico-chemical characteristics and thermal and electrical behavior of unaged and service-aged crosslinked polyethylene (XLPE) - insulated cables, and sections of the insulation obtained from this extruded cable. It has been demonstrated that volatile components generated primarily from the peroxideinduced crosslinking process can be defined and quantitatively measured. The morphology of the aged and unaged XLPE extruded insulation can be defined, and the thermal behavior on a micro (morphology changes) and macro (cable aging) level compared. Changes in microvoid level due to melting and recrystallization during cable operation appear to correlate with the limited amount of ac breakdown strength data obtained, and thermal overload of the cable conductor causes complete melting (and recrystallization on cooling) reducing the microvoid level. A single thermal overload alters the morphology but many thermal overloads are required to drive off the volatiles.
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  • 5
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 23-28 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Most polymers are eroded rapidly (〉0.1 μm/h) in the low earth orbit (LEO) environment when facing the direction of flight. The rate of erosion varies little with the polymer type, except for fluoropolymers and silicones. Methods for simulating such an environment are reviewed. Secondly, the oxidation lifetime of stabilized and unstabilized polyolefins can be reduced 50 to 90 percent, with a, high yield of carboxylic acid (i.e. chain scission) oxidation products, when thermal oxidation at 70 to 90°C takes place in 0.01 to 0.1 molar sodium chloride solutions, as compared to thermal oxidation in air. Both sets of observations illustrate the need for detailed mechanistic investigations before accelerated test procedures can be developed to predict material lifetime.
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  • 6
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 19-22 
    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: The kinetic parameters of the thermal decomposition of poly(aryl-ether-ether-ketone) (PEEK) in a nitrogen atmosphere have been obtained using an isothermal weight-loss method. Several mathematical approaches have been used to obtain the Arrhenius parameters based upon the use of different reaction models. The values obtained for the activation energy (E = 198.4 to 219.7 kJ/mol) and preexponential factor (log A = 11.1 to 12.3 min-1) fall within a narrow range, irrespective of the method of calculation. Although the kinetic data most closely fits an Avrami two-dimensional nucleating model, the data can be just as easily described by a first-order rate law.
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  • 7
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 100-106 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The present paper describes the evaluation of nonlinear thermally induced residual stresses in the cooling of polymer melt during injection molding of plastic components. The computational methodology adopted is based on the transfinite element approach, which is a hybrid scheme as it combines transform methods and classical Galerkin schemes with finite element formulations to preserve the modeling versatility. The applicability of the proposed formulations for understanding the physics and the nature of the nonlinear thermally induced stresses in the solidifying process of a sample amorphous polystyrene specimen demonstrates the basic capabilities and potential of the methodology. Results obtained agree qualitatively well with earlier research studies and experimental findings relevant to thermally induced residual stresses in the injection molding of plastic components.
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  • 8
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 107-112 
    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: An approach to realize the reinforcement of a thermoset system at the molecular level by rigid-rod polymers was investigated. A mixture of bisbenzocyclobutene (BCB)-terminated imide oligomers constitutes the thermosetting component, and the rigid-rod polymer utilized in the present study was poly(p-phenylene benzothiazole) (PBT). The cure chemistry of the thermoset materials is based on the ability of benzocyclobutene functions to homopolymerize under the influence of heat. Thermal properties as well as film processing and mechanical properties of PBT/BCB thermoset composites are presented.
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  • 9
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 140-150 
    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: In this paper, we describe the preparation and structural characterization of biaxially oriented poly(p-phenylene sulfide) (PPS) films. These films were prepared in a biaxial stretching machine at various stretching temperatures, rates, and stretching ratios. Selected samples were constrained annealed at elevated temperatures. The state of orientation was determined by wide angle X-ray diffraction (pole figure determination) and birefringence measurements. The results are expressed in terms of the biaxial orientation functions (ƒ1cB,ƒ2cB). Mechanical properties (tensile modulus, tensile strength, and elongation to break) were obtained as a function of processing conditions and direction in the plane of the films.
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  • 10
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 171-177 
    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 method has been developed to measure the three-dimensional temperature distribution of polymer melts in the reservoir of the heating barrel in the dynamic state. The procedure involves the use of a small-sheathed thermocouple in the nozzle of the machine. The tip of the thermocouple can be varied in depth from the surface to the center of the nozzle. The polymer melt of a shot is found to have a three-dimensional temperature distribution dependent on the geometry of the screw and the order of shot. These results reflect clearly the thermal histories of the polymer melt in the channel of the screw during plastication and conveyance, and indicate part of the dynamics of injection molding. Further, these measurements contribute to optimization of the design for the screw and the process conditions.
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  • 11
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 77-81 
    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 Fourier Transform Infrared spectrometer equipped with a microbeam accessary and a linear translation stage with a pinhole mask was used to monitor the diffusion of antioxidant in crosslinked polyethylene (XLPE) matrices crosslinked with controlled amounts of crosslinking agent. Integration of the peak area for a characteristic peak of the antioxidant at different positions along the sample indicated the changing concentration due to diffusion within 30 days. This technique allowed us to study an antioxidant with a molecular weight in the thousand range. The diffusion coefficients calculated were in the order of 10-11 - 10-10 cm2·s-1. It was observed that the diffusion constants dramatically changed with the crosslinking density.
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  • 12
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 85-90 
    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 phase behavior of polyarylate blends with a copolyester based on poly(1,4-cyclohexanedimethylene/ethylene terephthalate) was studied by differential scanning calorimetry and dynamic mechanical analysis. A single glass-transition temperature was observed over the entire composition range. Up to 30% weight polyarylate, the copolyester crystallized readily and its melting point did not change with blend composition. This indicates that transesterification, if it occurred, was negligible. The thermal and dynamic results also suggest a weak polymer-polymer interaction in this system.
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  • 13
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 69-76 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Mechanical properties, deformation modes under both uniaxial tension and compression, low temperature mechanical relaxation behavior, and resistance to fracture under dynamic loading have been investigated for a medium impact grade of polystyrene, Shear yielding is the dominant mode of plastic deformation in compression while matrix crazing, together with some tearing and cavitation of the rubber phase, occurs in tension. The craze microstructure, as determined by transmission electron microscopy (TEM), is typical of that noted in polystyrene, with sharp craze-bulk interfaces and a characteristic midrib section. The presence of a third phase, possibly a processing aid, is evident in the TEM scans and in the dynamic mechanical data. The present data, together with the data obtained on polystyrene and on high impact polystyrene, are used to show the strong influence of rubber content on various mechanical properties, such as the tensile craze yielding stress, ductility, compression yield strength, degree of strain softening, and fatigue durability.
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  • 14
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 227-234 
    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 styrene-butadiene-styrene (SBS) block copolymers were cast into sheet form, and the resulting microphase-separated specimens were tested in tensile free recovery. After an initial strain of 300%, specimens were released and their lengths measured for about a week. For one polymer, the recovery curves are presented for seven temperatures in the range -40 to +80°C; other data are given at 22°C. Analysis of the recovery curves, using as the model a series assembly of Kelvin elements, obtains time constants for microstructural repair and explains the temperature dependence in terms of the microstructural interphase and its partial vitrification. Differences among the three polymers can be interpreted by recognition of styrene-block molecular weights, as well as by the volume fractions of the domain styrene cores and interphases. Additional structural information arises from torsion pendulum experiments over -120 to 100°C for unstretched, stretched (300%), and partially recovered samples.
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  • 15
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 214-226 
    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: Shear modification treatment represents a special shearing history affecting mainly the elastic behavior of polymer melts. This process has been attributed to reversible physical changes in the entanglement structure of the polymer chain network. Shear modification studies were performed for two well-characterized low-density polyethylene (LDPE) grades differing in molecular weight distribution and degree of long chain branching. The shear working of the material was carried out using a specially designed shearing unit producing definable amounts of pure shear in a continuous process. Measurements of the dynamic storage modulus, G′, steady-state shear compliance; Je, extrudate swell, melt flow index, and the extensional behavior (Rheotens test) indicate that primarily properties associated with the elasticity of the melt are reduced in value. The observed reduction is found to correlate with the mean specific energy dissipated during sample preparation. Comparing the two LDPE grades showed that higher degrees of modification can be obtained at lower energy input levels for the more highly branched grade. Reversibility tests were performed and complete recovery of the initial material behavior was observed. Comparison of measurement results for samples prepared using the shearing unit presented here and a Brabender Plasticorder indicates that the degree of modification depends not only on the molecular structure of the polymer but also on the manner in which the shearing history is imposed upon the material.
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  • 16
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 235-243 
    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 same three styrene-butadiene-styrene copolymers discussed in the companion paper (this issue) were tested by cycling in uniaxial tension/retraction, with large magnitude (to 600% in some cases) and different sequences and rates. The behavior of “set”, at the end of each retraction, is examined in detail and invoked to explain several other features of the stress-strain curves. Time scales for structural recovery determined in the companion paper are found to assist this interpretation. Quantitative modeling of the isostructure retraction curves is accomplished in terms of the Mooney-Rivlin strain function, modified to employ a strain variable amplified by the volume of broken glassy “filler”. Values of the two Mooney moduli G1 and G2 are used to infer various features of the microstructure.
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  • 17
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    Polymer Engineering and Science 29 (1989), S. 244-257 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Blends of polycarbonate (PC) and poly(ethylene terephthalate-co-p-oxybenzoate) (PET/PHB60) were prepared by melt-blending. Physical and/or chemical interactions between the two phases of the system were studied by thermal analysis and infrared spectroscopy. Rheological measurements in shear flow were carried out both in the low and high shear rate regions in the temperature range of the existence of the mesophase. At low liquid crystalline polymer (LCP) content, the blends showed flow curves similar to those of the unfilled PC, while at higher LCP percentages the rheological behavior of the pure LCP was resembled. Moreover, in the whole shear range, the viscosity values of such blends were in between those of the pure polymers. The influence of the addition of 10% LCP on the mechanical properties of the PC was investigated. Fiber-spinning was performed under different experimental conditions, and it was found that opportune drawing conditions are necessary to improve the modulus of the matrix. Morphological analyses of the pure LCP and of the blends were related to the rheological and mechanical behavior of these systems. While the LCP exhibited an elevated dimensional stability, the inclusion of the LCP in PC matrix did not improve the dimensional stability of the blends.
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  • 18
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 258-267 
    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 visualization experiments of polycarbonate and polystyrene resin extrusion were performed to observe the melting mechanism and the flow kinematics around the solid-bed in the melting zone of a single screw extruder. The axial solids content and pressure profile calculations of the Tadmor melting model were modified as a result of variable solid-bed velocity and solid-bed temperature observations.
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  • 19
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 273-274 
    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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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 268-272 
    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 problem of inhomogeneous swelling of polymers around particles or fibers is treated analytically within the context of Gaussian statistics for polymer chains and the Flory-Huggins approximation for the interaction between polymer and solvent. The resulting differential equation for the displacement field around the inclusions is quite simple; it contains a homogeneous part and a nonlinear part. The nonlinear part of the differential equation is preceded by a parameter n(1 - 2χ), where n is the molecular weight between crosslinks and χ is the Flory-Huggins interaction parameter. Accordingly, the displacement field for the case of theta solvent, i.e. χ equals 0.5, can be solved exactly. In good solvents, the problem can be treated as a perturbation of the theta solvent condition. The amount of deviation from the theta solvent solution is obtained through a numerical technique and the results are tabulated as a function of n(1 - 2χ).
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  • 21
    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 tensile test behavior of specimens taken from polypropylene discs injection-molded with and without packing, respectively, was studied. The initial state of the different layers of the specimens and their stressed state, respectively, are characterized by small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), measurements of birefringence and of mechanical properties, and by light-microscopic investigations. The results off these experiments altogether give a detailed representation of the behavior of the different layers of the specimens in the tensile test.
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  • 22
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    Polymer Engineering and Science 29 (1989), S. 846-849 
    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 concerns a more in-depth examination of the different components which make up positive photoresists based on the combined principles of chemical amplification and dissolution inhibition. Included is a discussion of the requirements for materials to be used as dissolution inhibitors in this scheme as well as an example of an optimum compound-t-butyl-cholate. Also considered are the effects of onium salt counteranions on resist performance including gel permeation chromatographic (GPC) analyses of the changes in novolac molecular weight distribution which can occur during irradiation and postbake.
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  • 23
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    Polymer Engineering and Science 29 (1989), S. 993-1003 
    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 describes the development of process control schemes for the free radical initiated (reactive) degradation of polypropylene in an extruder (reactive extrusion). The objective of the work was to control the amount of degradation in order to produce polypropylene with a specified molecular weight. The die pressure drop was used as a measure of the amount of degradation (the measured variable) and the initiator concentration was used to control the amount of degradation (the manipulated variable). The reactive degradation process was modeled empirically to determine the dynamic relationship between the input degradation initiator concentration and the output die pressure drop. Several control schemes were evaluated for controlling the die pressure drop (amount of degradation) with emphasis placed on schemes designed to overcome the non-linear process gain and dead time.
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  • 24
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    Polymer Engineering and Science 29 (1989), S. 965-971 
    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: Materials and processing are described that provide 0.5 μm resolution with between 1 and 2 μm total depth of focus using a 436 nm stepper with 0.42 N.A., using the previously described PIE process (SPIE 631, 171 (1986)); 0.4 μm lines, spaces, and line/space gratings were reproduced. The chemistry is based on the photobleaching of anthracene derivatives in the presence of oxygen, followed by a deep-UV pattern transfer exposure under nitrogen. Although resolution and process control are quite good, the exposure time of 1.2 s is somewhat long due to the limited oxygen permeability of the chosen polymer; in addition the strong unbleachable absorbance of the deep-UV resist limits the usable thickness to ∼500 nm. Materials have been identified that promise to overcome both limitations, yielding thicknesses of 1 μm or more and exposure times less than 500 ms. Application to 365 and 248 nm imaging is also possible.
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  • 25
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    Polymer Engineering and Science 29 (1989), S. 1097-1102 
    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: Nonisothermal differential scanning calorimetry (DSC) measurements were used to estimate the kinetic parameters for the curing reaction of a commercial unsaturated polyester resin. The reaction rate expression was derived from a mechanistic kinetic model based on the concept of free radical polymerization, accounting also for the diffusion controlled reaction. The total heat of reaction was evaluated in experiments run at very low scan speeds and using high amount of initiator. The kinetic parameters were found to show no dependency on the heating rate nor on the initiator concentration. Dynamic DSC measurements provide reliable kinetic data over a broad range of temperatures that is mostly significant for process simulations.
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  • 26
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    Polymer Engineering and Science 29 (1989), S. 359-365 
    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(ethylene terephthalate) (PET) and bisphenol-a-polycarbonate (PC) are known to form a miscible blend whereas ternary blends of PET, PC, and polypropylene (PP) form two phases. This is based on the considerations of various chemical events which may occur in these systems. The role of ester-carbonate interchange reactions during melt mixing and fabricating is found to be unimportant. Differential scanning calorimetric analysis of the ternary blends shows that there appears to occur an exothermic transition in the heating mode of the instrument. This exothermic event was found to be suppressed considerably by incorporating suitable additives into the system. Degradation reactions studied by thermogravimetric analysis and a dilute solution viscometric technique reveal that there exists some kind of interaction among the components even with the immiscible PP component.
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  • 27
    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: Acetalized poly(vinyl alcohol)s which were synthesized from poly(vinyl alcohol) (PVA) and aldehyde or ketone were evaluated as electron beam (EB) resists, in order to investigate the relationship between EB sensitivity and chemical structures of the polymers. It was found that the acetalized PVAs were easily crosslinked by EB exposure. The main mechanism of crosslinking may be radical reaction at acetal group. The sensitivity of the acetalized PVA depended on the structure of the acetal group. Acetalized PVAs synthesized from benzaldehyde, in which the electron attracting group was substituted on the benzene ring and from linear aliphatic aldehyde having a long alkyl chain, had high sensitivity. A high sensitivity of 7.2 × 10-7 C/cm2 was attained when the acetalized PVA synthesized from p-chloro-benzaldehyde was used. Acetalized PVAs synthesized from PVA and aldehyde having a cyclic structure had an excellent dry etching durability and were suitable as negative EB resists.
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  • 28
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    Polymer Engineering and Science 29 (1989), S. 366-373 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The glass transition temperature has been measured carefully for the fluoroelastomer, Tecnoflon, a copolymer of vinylidene fluoride and hexafluoropropene, diluted with variable amounts of 2-butanone. Of the several different theoretical treatments found in literature, that presented by Gordon and coworkers appears to give the equation that describes well the experimental results, without making use of adjustable parameters. Some features found at very high diluent content can be interpreted with a treatment based on free volume.
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  • 29
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    Polymer Engineering and Science 29 (1989), S. 374-382 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This work proposes a cascade model reference adaptive algorithm to control a continuous polymerization reactor, which is operated under forced oscillations of its feeds. The objective is to produce a polymer with desired average values of the average chain length, of the average polydispersity and of the average polymer production; in spite of the fact that some of the model parameters may be unknown and/or may vary slowly with time. This objective is achieved by imposing the first two moments of the number chain length distribution (NCLD) to follow predetermined periodic trajectories. The proposed control scheme is an extension of that by Eliçabe, et al., when the number of independent controls is less than the number of system states. Computer simulations have shown the feasibility of the proposed technique, provided continuous state measurements are available.
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  • 30
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    Polymer Engineering and Science 29 (1989), S. 383-389 
    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: Ultrahigh molecular weight polyethylene (UHMWPE) gel films were prepared by gelation crystallization from decalin solutions. According to wide- and small-angle X-ray scattering (WAXD and SAXS) studies, single crystal mat texture with crystal c-axis oriented normal to film surface generally develops. However, randomly oriented structure can also develop if an external force is applied to gel films during gelation crystallization. Both textures invariably yield high drawability in uniaxial mode with outstanding modulus and strength. Biaxial films, typically 5 × 5, 6 × 6, 8 × 8, and 10 × 10 times the original dimensions, were prepared at 130°C-135°C in a biaxial stretcher. Optical microscopic Investigations reveal the development of interwoven fibrillar structure in all specimens. WAXD and SAXS studies show that lamellar structure transforms to fibrillar texture during biaxial stretching. Crystal orientation is characterized by WAXD pole figure and infrared dichroic methods. Mechanical studies suggest that tensile modulus and strength appear uniform. In comparison with uniaxial deformation, significant improvement in the lateral strength is seen in the biaxially stretched films.
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  • 31
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    Polymer Engineering and Science 29 (1989), S. 390-396 
    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 molecular weight distribution on the Theological and mechanical properties of a series of polypropylenes is evaluated. The polypropylenes tested were produced by controlled chemical degradation in a single-screw plasticating extruder. Measured properties include shear, extensional and intrinsic viscosity, melt flow index, extrudate swell, melting and crystallization temperatures, impact strength, flexural modulus, and tensile stress.
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  • 32
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    Polymer Engineering and Science 29 (1989), S. 397-404 
    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: Interpenetrating polymer networks of polyurethane and unsaturated polyester were prepared by reaction injection molding (RIM) and transfer molding. The structures of the molded samples were analyzed by electron microscopy and dynamic mechanical analysis. It was found that polymer morphology and dynamic mechanical properties depend strongly on the molding temperature, reaction rate and reaction sequence. Simplified structure models based on Takayanagi's model and sample morphology can predict the storage modulus reasonably well but not the tanδ.
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  • 33
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    Polymer Engineering and Science 29 (1989), S. 1200-1204 
    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 gradient-index (GRIN) plastic optical fiber was prepared by a heat-drawing process of the GRIN preform rod obtained by a new interfacial-gel copolymerization technique. The attenuation loss of the GRIN fiber was 179 kB/km at 650-nm wave-length and its numerical aperture was 0.20-0.25. To attain low loss and highly dense integrated circuits, steric radial-GRIN optical waveguide components such as GRIN branching, star coupler, multi-coupler, and a 2-D GRIN lens array, were monolithically fabricated by this technique. A novel spherical GRIN sphere lens, whose index function is symmetrical about the center of the sphere, with a low spherical aberration, was prepared by a modified suspension polymerization technique. A W-shaped GRIN sphere has been newly proposed to further reduce the spherical aberration, compared with the parabolic GRIN sphere previously proposed.
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  • 34
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    Polymer Engineering and Science 29 (1989), S. 415-419 
    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: Melt temperature in an extrusion process can significantly influence production rate, product quality, and yield. However, prediction of melt temperature is extremely difficult because errors in the predictions of output rate, screw power, and heat transfer, which are used to calculate melt temperature, cumulatively cause a very large error in the prediction of melt temperature. This paper analyzed the overall energy balance of an extruder and developed a simple equation to predict the melt temperature of a projected extruder in scale-up as a function of screw diameter, depth, and speed based on the experimental results of an experimental extruder and the polymeroperties. The predicted melt temperatures agreed reasonably with the measured values reported in a previous scale-up study.
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    Polymer Engineering and Science 29 (1989), S. 433-440 
    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 Newtonian and non-Newtonian fluids which obeys a power law relationship between shear stress and shear rate has been modeled in the melt conveying section of a self-wiping co-rotating twin-screw extruder using a finite element analysis of an unwound channel section. Predictions of throughput against pressure gradient are compared with experimentally obtained results for maize grits which is represented as a power law material. Rheological data applicable to extrusion simulation were obtained from capillary rheometry. Comparisons are reasonable with predicted characteristic showing similar behavior.
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  • 36
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    Polymer Engineering and Science 29 (1989), S. 1298-1307 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Specimens of two engineerig plastics i.e., poly(ether imide), PEI, and poly(2,6-dimethyl- 1,4-phenylene ether), PPE, were injection molded employing a 40t Van Dorn injection molding machine and industrial practices. The mold and melt temperatures and the injection speed were varied in a limited range which furnished acceptable samples. The density, birefringence, residual stress distributions, flexure and tensile properties, and crack development of the injection molded specimens were studied. Vacuum compression molded samples were also prepared to investigate the role played by the cooling rate in shaping microstructural distributions. The results revealed significant differences in the development of microstructure of the molded specimens of the two resins, which was related to rheology and molding conditions on one hand and to development of cracks and ultimate properties on the other hand.
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    Polymer Engineering and Science 29 (1989) 
    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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  • 38
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    Polymer Engineering and Science 29 (1989), S. 1325-1331 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In structures composed of polymer matrix composite materials, components must be joined such that the overall structure retains its structural integrity while it is performing its, intended function which can include both mechanical loads (static and dynamic) and environmental loads (temperature and humidity). The use of composite materials in complex structures almost always reduces the number of components in the structures compared to the use of metallic alloys for the same structure. Thus, using composite materials not only results in great savings in weight, but also through a reduced number of joining operations, results in significant savings in assembly, inspection, parts storage, and movement, resulting in increased reliability and lower cost. Yet joining is still required. Joining metallic structures is a mature technology involving riveting, bolting, welding, glueing, brazing, soldering, and other methods. However, for most polymer matrix composites only adhesive bonding and mechanical fastening can be utilized. Attention has been given recently, however, to localized welding of thermoplastic polymer matrix composites, and this will be discussed briefly later. Inherently, adhesive bonding is preferable to mechanical fastening because of the continuous connection, whereas in drilling holes for bolts or rivets, fibers or other reinforcements are cut, and large stress concentrations occar at each discrete fastener hole. The following is a review of much of the literature dealing with adhesive bonding of polymer matrix composite structures. It is Intended not only to be a review, but also a background for detailed study of the referenced and other documents, and a catalyst for future research.
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  • 39
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    Polymer Engineering and Science 29 (1989), S. 463-470 
    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 was carried out of the development of orientation during processing of conventional blow molded bottles made from low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE). The level of molecular orientation was found to be relatively low in all of the polyethylene bottles examined; it increased with increasing inflation pressure and decreasing extrusion temperature. Pole figures for the HDPE bottles indicated a slight a-axis orientation toward the circumferential direction of the bottle. The b-axes, which correspond to the lamellar growth direction, tend to be parallel to the bottle thickness direction. A comparison was made of the structure developed in blow molded bottles and blown films. The results for both films and bottles indicate that crystallization during processing involves both an increase in level of molecular orientation and an increased tendency toward biaxiality. Based on pole figures and small angle X-ray scattering patterns, a morphological model for HDPE blow molded bottles is proposed.
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  • 40
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    Polymer Engineering and Science 29 (1989), S. 1387-1395 
    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 integrity of a pipeline system is determined by its weakest links. Joints may be such places. Heat fusion is the most common joining method for distribution gas piping. There are procedural, thermal, and mechanical aspects of making fusion joints. Procedural aspects, such as heater calibration and cleanliness, can be assured only by rigorous training and certification of the operators. Thermal and mechanical aspects consist of specifying joining conditions such as the heater temperature, heating time, and joining pressure. In the absence of procedural errors, the strength of a fusion joint should depend on the pipe material, pipe dimensions, and the thermal and mechanical joining conditions.The measured parameters that are measures of strength are impact energy and location of failure in the tensile impact test. A parameter, termed the joining parameter, was found to characterize the joining conditions. This parameter is a function of bead volume, melt volume at the end of the heating phase, and pipe wall thickness. Of the mechanical test parameters, the impact energy was found to correlate best with the joining parameter.
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  • 41
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    Polymer Engineering and Science 29 (1989), S. 1413-1418 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A variety of thermoplastic fully imidized poly(imide siloxane) segmented copolymers with useful thermal and mechanical properties have been prepared. Other interesting properties described are the materials' hydrophobic character, surface domination, UV stability, and atomic oxygen plasma resistance.
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    Polymer Engineering and Science 29 (1989), S. 1426-1433 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We demonstrate the use of computer vision techniques and optical microscopy to follow the kinetics and microstructure during spinodal decomposition of a polymer blend. Among other features, the mean of the population of the local maxima of the gradients in each image is computed; this global feature is shown to co-develop with the phase separation of the blend. An algorithm is presented which employs the gradient magnitude technique to analyze optical images of spinodally decomposing polymer blends. This algorithm has been used to extract the Cahn-Hilliard spinodal growth rates for a binary blend of polystyrene with poly(vinyl methyl ether). We show that the spinodal temperature can be found from the temperature dependence of this growth rate. We also show how additional shape features such as compactness might be used to study, the same binary blend.
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    Polymer Engineering and Science 29 (1989), S. 493-498 
    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 kinetics of nylon-6 and nylon-6 block copolymers (NBC's) containing 1-3 mole % poly(ethylene oxide), PEO, were measured under isothermal and linear cooling conditions. The Avrami equation was used to fit the data. The range of the Avrami index n was from 1.5 to 2.2 for the system studied in the temperature range from 400-454 K. Maximum rate of crystallization was observed in the above temperature range. Nylon-6 block copolymers showed the maximum crystallization rate at a lower temperature than nylon-6. When the soft segment exceeded 3 mole %, no crystallization was observed. Cooling rate studies showed the same tendency. The crystallization rate behavior of nylon-6 block copolymers was similar to the pure nylon.
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  • 44
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    Polymer Engineering and Science 29 (1989), S. 505-512 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The impact fracture energy (Gc) for a polypropylene homopolymer and a copolymer with and without calcium carbonate fillers was measured over a range of temperatures between -40°C and 40°C using fracture mechanics principles. The fillers studied were Omyacarb (∼2.7 μm) and Winnofil (∼75 nm) and 10% by weight was added to the matrix material. These fillers did not have any appreciable effect on Gc of the copolymer-based composites. However, the Omyacarb fillers improved Gc of the homopolymer at low temperatures (≤20°C) due to enhanced microplastic flow as observed on the fracture surfaces. The fillers increased the stiffness of both the homopolymer and copolymer. It would appear that up to 10% of cheap calcium carbonate fillers could be added to the more expensive polypropylene to reduce the production cost without any significant loss of impact fracture energy.
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  • 45
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    Polymer Engineering and Science 29 (1989), S. 499-504 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A novel sliding plate rheometer has been developed that is suitable for use with molten plastics, concentrated polymer solutions, raw elastomers, and other viscoelastic or thixotropic materials. It can generate steady shear rates from 0.05 to 500 s-1 and can also be used to measure linear viscoelastic properties. In addition, it can be used to measure a broad spectrum of nonlinear viscoelastic properties such as the nonlinear relaxation modulus and the shear stress growth coefficient. In order to measure these nonlinear properties it is necessary to generate large, uniform, transient deformations Involving high strain rates. Rotational and capillary melt rheometers are not capable of generating this type of deformation, and until now it was not convenient to use sliding plate rheometers for this type of application. However, the recent development of a reliable and robust shear stress transducer makes it very convenient to use the sliding plate geometry to carry out all of these tests. The new rheometer is described, and examples of the types of data it can generate are shown.
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    Polymer Engineering and Science 29 (1989), S. 1524-1527 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The present paper describes an analysis of the orientation developed in biaxially stretched polystyrene films in terms of the kinematics of the process and a viscoelastic constitutive equation. It was possible to achieve reasonable agreement of predicted and experimental birefringences through use of a convected Maxwell model and the Rheo-Optical Law.
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    Polymer Engineering and Science 29 (1989), S. 1544-1550 
    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: Five blends of polycarbonate (PC) with linear low density polyethylene (LLDPE) were studied. Characterization of the blends was made by means of rheological measurements and domain morphology determined by SEM microscopy. A fine dispersion was obtained for the 25/75 PC/LLDPE. The blends were then oriented, LLDPE and 25/75 PC/LLDPE at room temperature, and the others at 165°C. For the hot drawn blends (50/50 and 75/25 PC/LLDPE), a significant increase in tensile strength and elongation at break is observed. For the room temperature drawn samples, modulus and tensile strength values increase whereas elongation at break decreases. This is explained in terms of morphological and molecular orientation effects. Comparison of the experiments to the predictions of different models for the modulus shows a good agreement for unoriented blends. However, for oriented samples, important discrepancies are observed, suggesting that the morphology and orientation are important factors in predicting the modulus of these blends. A model which takes into account these factors is proposed and a good fit of the modulus is obtained.
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    Polymer Engineering and Science 29 (1989), S. 1569-1573 
    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 gel melting temperature and crystallization kinetics of ultra-high molecular weight polyethylene (UHMW-PE)/decalin systems were investigated. Two methods were used to determine gel melting temperature; thermomechanical analysis (TMA) with a penetration probe and differential scanning calorimetry (DSC). The melting points determined from TMA and DSC were in good agreement, indicating that the crystallization of UHME-PE is an essential step for gelation. The gel melting temperature increases with UHMW-PE concentration. The change in gel melting temperature with composition results from interaction of the components in the amorphous phase. The gelation and crystallization rates increase with decreasing UHMW-PE concentration.
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    Polymer Engineering and Science 29 (1989), S. 1574-1578 
    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 optical properties of polyetherimide resin as described by the complex index of refraction, N = n - ik, are derived by Kramers-Kronig analysis of experimental absorption and reflectance data obtained in the range 40 μm ≥ λ ≥105 nm. Potential uses of this polymer as a printed circuit board material and as a packaging medium for microelectronic circuitry and the relevance of optical data in laser-assisted processing schemes used in these and other applications are briefly discussed.
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    Polymer Engineering and Science 29 (1989), S. 1588-1591 
    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 strain-time response under tensile loading (creep tests) and the stress strain response under constant tensile stress rate (proportional loading tests) have been evaluated at 4 temperatures 20, 45, 55, and 65°C, for samples of cellulose nitrate. A time-dependent constitutive equation (or stress-strain relation) for the nonlinear visco-elastic material is deduced from invariant theory with a hypothesis of a creep potential. The procedure for determining the seven material constants involved in the deduced constitutive equation is described for the creep and proportional loading tests and the variation of these constants with temperature is presented. The deduced constitutive equation gives good agreement with the actual observations for the creep and proportional loading tests, independent of the values of temperature, creep stress, or stress rate.
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    Polymer Engineering and Science 29 (1989), S. 1604-1610 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An investigation of the effect of physical aging on excess enthalpy of compatible polymer blends was carried out. Poly(methyl methacrylate) (PMMA) and poly(styrene-co-acrylonitrile) (SAN) were chosen for this study. Blends of different ratios of PMMA and SAN were physically aged at different times and temperatures below their glass transition (Tg) and then subjected to enthalpy relaxation measurement in a differential scanning calorimeter (DSC). An improved procedure was developed and, employed to analyze the data. The error associated with the calculation of the normalized deviation in enthalpy, known as the “Φ” function, was below 4%. The relaxation was observed to proceed faster at higher aging temperature. It was also found that at higher aging temperatures of Tg - 20 and Tg- 35°C, enthalpy relaxation in SAN-rich blends proceeds faster than in PMMA rich blends, while at the low aging temperature of Tg- 50°C the rate of relaxation becomes independent of the composition.
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    Polymer Engineering and Science 29 (1989), S. 1618-1627 
    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 statistical procedure is proposed to identify sources of variation in the operation of complex extrusion lines. This approach involves separating multichannel extrusion line data, as necessary, into appropriate time scales; identifying significant cross correlations among various pairs of channels; and then comparing the pattern of the observed cross correlations with those expected for possible sources of variation. This procedure is able to detect unsuspected relationships among processing variables and to provide a rational basis for upgrading extrusion line performance. The pattern generation and comparison methodology could also be useful for expert systems. To illustrate the procedure, 11 channels of data from a dual extrusion line with metered feed were collected and analyzed. Since two sources of variation on different time scales were evident, the data were divided into long-term and short-term components using statistical methods. Cross correlation functions among pairs of variables were used to estimate offset times and identify variables that were significantly correlated. To be considered significant, the extremum in the cross correlation function had to occur at a realistic time offset and have an absolute value exceeding a prescribed threshold. The observed cross correlations between pairs of short-term and of long-term components were compared with the expected correlation patterns for typical process disturbances. By this procedure, the cause of the short-term trends was identified as surging primarily in the larger extruder; a particular long-term trend was attributed to a property change in the feed material to the smaller extruder. This analysis formed the basis for a novel process control device to minimize the consequences of short-term variation in extruder output.
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    Polymer Engineering and Science 29 (1989), S. 1637-1637 
    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 29 (1989) 
    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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  • 55
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    Polymer Engineering and Science 29 (1989), S. 1649-1654 
    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: Welding represents one of the key stages in the manufacture of injection molded or blow molded plastics products. One process frequently employed is heated-tool butt welding. However, the high seam quality associated with this process can only be attained through reliable process control and optimized welding parameters. This paper presents a simple new method for determining these parameters. Mathematical and physical descriptions of the individual process stages and a computer-controlled heated-tool butt welding machine serve as the basis for determining the parameters.
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    Polymer Engineering and Science 29 (1989), S. 1661-1666 
    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 measuring method is presented for process monitoring and process analysis of linear vibration welding of thermoplastics. The method works by recording and evaluating time-dependent signals that describe the process - such as the frequency-dependent signals of the displacement of the two parts being joined, the tangential force in the welding plane - and the nonperiodic signals of the welding process, i.e. the normal force in the welding plane and the melting or joining displacement of the parts being joined. It is possible to determine the energy input into the welding zone as a function of the selected machine parameters and the process sequence over time.
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    Polymer Engineering and Science 29 (1989), S. 1677-1682 
    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 made of vibration butt welds between plaques of polypropylene. The quality of the welds, as determined by impact tests, has been examined as a function of the welding variables: pressure and vibration amplitude. In addition, the microstructure of the welds has also been examined, classified, and correlated with the welding variables and weld quality. Penetration as a function of time shows three distinct regimes and It is shown that the impact strength of the welds is independent of time once the third regime is reached. The time required to reach the third regime decreases as pressure or amplitude increases and is more sensitive to amplitude of vibration than to pressure. The highest quality welds were produced at low pressure and low amplitude with corresponding long times to reach regime three and exhibited a unique, readily identifiable microstructure.
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    Polymer Engineering and Science 29 (1989), S. 1722-1729 
    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 transient two-dimensional thermal model for resistance welding of thermoplastic composites is presented. A parametric study is conducted that yields insight into the welding process enabling some critical process and material parameters to be identified. Time to melt is predicted by the model and is successfully compared to experimental observations. Local heating and meltthrough can also be explained by the transient thermal model in agreement with experimental observations. Mode I fracture toughness of unidirectional graphite reinforced poly(etheretherketone) resistance welded double cantilever beam specimens are conducted under various process conditions. Experimental results indicate that under optimum process conditions, the interlaminar fracture toughness of the bulk compression-molded thermoplastic composite material can be achieved using resistance heating as a joining technique.
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  • 59
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    Polymer Engineering and Science 29 (1989), S. 639-644 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Calculation of gas permeation in food packaging structures can be done using a steady-state analysis employing the permeability coefficient. While this approach is adequate for some applications, for many others a time-dependent transport analysis must be considered to make quantitative predictions of shelf life. The limitation of the simple permeability analysis for multilayer structures is illustrated for Saran-coated polycarbonate and poly(ethylene terephthalate) soda cans. These more detailed calculations on package structures can be done using standard computer library routines to include both the effect of gas sorption and diffusion.
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    Polymer Engineering and Science 29 (1989), S. 645-653 
    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 methodology has been developed to determine molecular weight distributions (MWD) from dynamic rheometry data. The present work extends and modifies previous results and illustrates that the MWDs of tetrafluoroethylenehexafluoropropylene copolymers (FEP) are broader than previously thought. The major change in methodology involves the relationship between a reduced form of the elastic shear modulus as a function of frequency, G′(ω), and the cumulative weight fraction as a function of molecular weight. The new method uses a square root versus the former linear relationship. Spectroscopic analysis of the end group concentration was used to determine the number-average molecular weight. These data were used to reference the MWDs determined by dynamic rheometry and indicate that the molecular weights of these polymers are 20% lower than previously found.
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    Polymer Engineering and Science 29 (1989), S. 671-678 
    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 fracture toughness characterization of four impact-modified polymers based on the J-integral concept was studied. We have discovered that the use of the “crack blunting line” concept needs revision. Direct measurements of the crack growth can be made (as opposed to indirect readings from the fracture surface) that test the applicability of the crack blunting concept. Our results indicate that for rubber-toughened polymers the use of the blunting line fails to specify properly the critical J-integral value for crack initiation.
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    Polymer Engineering and Science 29 (1989), S. 662-670 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of physical aging on viscoelastic properties was studied for several cross-linked epoxies in the glassy state. Tensile creep and tensile stress relaxation were measured during isothermal physical aging, following rapid quenching of samples annealed above the glass-transition temperature (Tg). The momentary creep curves measured at 21°C, 45°C, and 61°C below Tg for different epoxies could be fitted to an empirical equation for the creep compliance D(t): \documentclass{article}\pagestyle{empty}\begin{document}$$ D(t) = D(0)\exp [(t/t_o)^\beta]. $$\end{document} Values for β and to were obtained, and the dependence of to on the aging time was determined. Shift factors were calculated to investigate changes in molecular mobility during physical aging. The momentary stress relaxation was measured on the same epoxy materials as used for the creep studies. The stress relaxation curves were fitted to the following equation for the tensile modulus E(t): \documentclass{article}\pagestyle{empty}\begin{document}$$ E(t) = E(0)\exp [-(t/t_o)^\alpha]. $$\end{document} Values for α and to were obtained. The influence of physical aging on-to was again studied by calculating shift factors as a function of the aging time. The results are compared with the results of the creep tests and discussed in the context of current molecular theories of physical aging of glassy polymers.
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    Polymer Engineering and Science 29 (1989), S. 679-684 
    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 morphology of polyamide 12 and polyether block amide blends was investigated by electron microscopy and dynamic mechanical techniques. The blends are not miscible, and phase segregation is observed. In each phase, the lamellar structure of the pure components is observed. The stability of these micro phases is pointed out. When the mass ratio of the hard and soft sequences in the block copolymer is about 4, a partial miscibility takes place.
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    Polymer Engineering and Science 29 (1989), S. 685-689 
    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 general purpose finite element program was used to study polymer extrudate swelling. It is shown that viscosity variations due to externally applied cooling or heating have a significant influence on the swelling ratios of axisymmetric and planar extrudates. The effect is more pronounced at high Peclet and Weissenberg numbers. Swelling due to thermal effects and swelling due to viscoelasticity are not additive because of interrelations between the various mechanisms.
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    Polymer Engineering and Science 29 (1989), S. 690-698 
    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: Structure-property relationships of polyester matrices containing various low profile additives such as poly(vinylacetate), polyurethane, poly(methyl methacrylate), polystyrene, and polycaprolactone were studied. The morphology and particle size of the dispersed phases in the polyester matrices are very dependent upon the type of low profile additives incorporated in the cured resins. Microvoids which are responsible for the degradation of physical properties of resin matrices are usually observed in the polyester phase and/or the dispersed phase of the low-profile resin matrices. Low profile additives, in general, lower the glass transition temperatures of polyester matrices, slightly increase the loss moduli and the loss factors, and slightly decrease the storage moduli. These polymeric additives also degrade tensile properties and improve the fracture toughness of polyester matrices, but do not have significant effects on the thermal stability.
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    Polymer Engineering and Science 29 (1989), S. 701-708 
    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 fluid dynamics analysis package - FIDAP - using a finite element method was employed to simulate the flow patterns in a Banbury mixer. The flow simulations were carried out only for the intensive mixing region, and they were limited to a two-dimensional analysis. A Lagrangean point of view was adopted and 18 different geometries were selected to represent one revolution of the rotor. A power-law model with time and temperature dependent parameters was used to characterize the rheological behavior of the mixture. Steady-state, isothermal flow simulations as well as a transient, non-isothermal flow analysis were performed for a Banbury B mixer. The results of the analysis show good agreement with experimental observations regarding the development of vortices, the pressure, and the temperature profiles.
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    Polymer Engineering and Science 29 (1989), S. 709-714 
    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 concerned with Newtonian flow in a counter-rotating non-intermeshing twin-screw extruder. Both the matched and the mismatched screw flight configurations are considered. A three-dimensional analysis of the pressure flow through the complete extruder cross-section is included. The model predictions agree well with the experimental data. Computed examples are given to illustrate the utility of this work.
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    Polymer Engineering and Science 29 (1989), S. 731-739 
    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 flow-induced stresses in extruded sheet made of polypropylene was analyzed. A theoretical model was developed to simulate velocity, temperature, and stress profiles for polymeric materials flowing inside a slit die. The output of this simulation was then used to compute temperature and stress profiles as the extrudate emerged from the die, cooled, and relaxed under no draw conditions. Simulated surface stresses and stress profile across the extruded sheet agreed well with the experimental data for the die temperature effect and the die gap effect at low draw ratios.
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    Polymer Engineering and Science 29 (1989), S. 722-730 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The extrudate swell effect has not received sufficient attention in modeling the film blowing process. This effect is addressed in this paper, and as an ab initio study, only viscous fluids were considered. The problem region was separated into two zones; the extrudate swell zone and the film blowing zone. The annular extrudate swell problem was solved using a finite element method. The film blowing process was modeled following Pearson and Petrie's (4) work. Although only viscous fluids were considered, the simulation results show a remarkable difference when swelling was included in the modeling. Viscoelastic fluids, which are more realistic for polymer melts, were not investigated here because of the so called high Weisenberg number problem. This is an open area still under investigation.
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    Polymer Engineering and Science 29 (1989), S. 960-964 
    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: A new approach to resist materials that exhibit chemical amplification is based on systems comprised of three structural units at least one of which is polymeric: (a) an aromatic moiety such as poly(4-hydroxystyrene), Novolac, or other aromatic compounds which are susceptible to electrophilic aromatic substitution; (b) a latent electrophile which may be polyfunctional and, in the case of this study, is a carbocation precursor; (c) a material which generates strong acid upon irradiation. Exposure of a film containing these three structural components affords a latent image of acid dispersed in the polymer matrix. In a subsequent baking step, the photogenerated acid reacts with the latent electrophile releasing a very reactive carbocationic species which becomes bound to the aromatic moiety. As one of the components of the resist is polymeric and multifunctional, the result is a rapid increase in molecular weight due to branching and crosslinking of the chains. In terms of imaging, this process translates into the formation of a negative image of the mask although under some conditions a positive image may also be produced. The system shows a very high sensitivity and can provide high resolution images devoid of distortion due to the absence of swelling during development.
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    Polymer Engineering and Science 29 (1989), S. 1124-1130 
    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 apparatus has been constructed in which ultrasonic velocity and attenuation coefficients can be measured under oscillatory deformation. Using this apparatus, dynamic ultrasonic parameters were obtained with sufficient accuracy to investigate plastic deformation directly. It is found that this method has potential as a new tool for the study of solid polymers during deformation.
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    Polymer Engineering and Science 29 (1989), S. 1165-1168 
    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 presented to study the mechanical behavior of soft, UV curable coating material as a function of temperature of the prepolymer at cure. For such materials, the crosslink density (hence, equilibrium modulus) is found to decrease with increasing cure temperature. The three primary coatings are: a polyurethane acrylate with a nominal equilibrium tensile modulus of 200 psi, a polyurethane acrylate with a nominal equilibrium modulus of 1200 psi, and a non-urethane acrylate with a nominal equilibrium tensile modulus of 60 psi.
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    Polymer Engineering and Science 29 (1989), S. 1177-1181 
    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 thermo-oxidative aging of a polyether urethane lightguide primary coating has been studied in films and dual-coated fibers, In films, oxygen absorption is correlated with changes in modulus, yellowness, glass transition temperature, and sample weight. Thermal aging of fibers shows similar trends with regards to coating weight loss and discoloration as those observed with films. In addition, the force to mechanically strip the fiber follows the same patterns of change as the modulus of aged films. For both films and fibers, the time for onset of property changes varies inversely with temperature and can be delayed by the incorporation of an antioxidant.
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    Polymer Engineering and Science 29 (1989), S. 1186-1192 
    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: Young's Modulus and the thermal expansion coefficient are material parameters used to predict the low temperature contraction of a fiber optic cable. In the past, room temperature values for these properties were used to estimate this contraction. In this paper, these properties have been determined as functions of temperature. Using these properties, the overall expansion coefficient of the cable was determined as a function of temperature. This overall coefficient was integrated from room temperature to the low operating temperature of the cable to predict the contraction of the cable. In this way, the temperature variations in the materials properties were incorporated into the design, resulting in a more accurate determination of the low temperature contraction of fiber optic cable.
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    Polymer Engineering and Science 29 (1989), S. 1209-1214 
    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 discusses polymers for optoelectronics, especially plastic optical fibers (POFs) for near-infrared (near-IR) use and polymeric nonlinear optical materials expected for use as switching devices. Near-IR transmissible plastic optical fibers are investigated using fluorination and deuteration for conventional polymers. Among them pentafluoro-trideutero-styrene polymer core POF has excellent transparency in the near-IR region even after water vapor absorption. Nonlinear optical polymeric materials with excellent processibilities are also investigated. The third-order nonlinear optical susceptibility of poly-aromatic vinylene thin film was measured and revealed to have a higher susceptibility than previously reported.
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    Polymer Engineering and Science 29 (1989) 
    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 29 (1989), S. 1237-1240 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A novel process for the formation of biaxially balanced films of poly(p-phenylene terephthalamide) was developed. The liquid crystalline sulphuric acid solution is extruded through a slit die on a flat plate. The optically anisotropic to isotropic transition is generated by controlling the temperature and/or the water content in sulphuric acid before coagulation. The wet gel films are dried while holding their width and length constant. The films thus produced are transparent and biaxially oriented. Young's modulus of 12 GPa, tensile strength of 450 MPa, and elongation at break of 25% were obtained in the plane of the film. Such films which possess high dimensional and thermal stabilities are expected to be useful for new practical uses under severe conditions.
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    Polymer Engineering and Science 29 (1989), S. 1259-1264 
    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 poly(ethylene terephthalate) (PET) was studied by the methods of small angle light scattering, depolarized light intensity and density measurements. Spherulite growth rates and the overall rates of crystallization were determined at various temperatures. A detailed analysis of the crystallization course has been made with special emphasis on the early stages of crystallization. The results indicate that a significant amount of crystallization takes place in the extraspherulitie material during isothermal crystallization.
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    Polymer Engineering and Science 29 (1989), S. 1246-1258 
    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 recently developed mathematical technique for studying the parametric sensitivity of reactors is extended to include chain polymerization systems exhibiting the gel and glass effects, as well as physical property variations. The sensitivities of the two temperature maxima with respect to various parameters are computed. It is found that, for a sample system, poly(methyl methacrylate), all the sensitivities of the gel effect induced temperature peak attain their maxima at the same conditions - this leads to a generalized temperature sensitivity constraint applicable to reactor design or operation. This sensitivity boundary is associated with high conversions and high molecular weights. The analysis shows that the dimensionless propagation activation energy, ∊p, and the dimensionless initiation activation energy, ∊d, are the two most important parameters governing the system performance. Sensitivities of the gel effect-induced number average chain length peak with respect to various parameters are also obtained. Again, all of these chain length sensitivities show maxima at the same condition, leading to the concept of a generalized chain length sensitivity criterion of constraint. Most importantly, the temperature and chain length sensitivity boundaries are virtually identical.
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  • 80
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    Polymer Engineering and Science 29 (1989), S. 1279-1285 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The curing conditions determine the rheological changes in the resin during the lamination of prepregs into multilayered circuit boards. In order to specify the optimum curing conditions during lamination, it is necessary to understand the rheology of the resin as it cures. In this study, the chemorheological behavior of two commercial epoxy resins and one cyanate-based resin was characterized using an engineering model for the resin viscosity. A linear regression technique was used to evaluate the model parameters from the conditions at the minimum viscosity obtained during resin cures at constant heating rates. The technique was extended to predict the minimum viscosities reached by the resins when subjected to temperature conditions commonly encountered during lamination. The utility of the technique for specifying the curing conditions necessary to have a desired resin flow during lamination and for selecting resin systems for lamination based upon chemorheology has been demonstrated.
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  • 81
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    Polymer Engineering and Science 29 (1989) 
    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
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    Polymer Engineering and Science 29 (1989), S. 1579-1587 
    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 general kinetic model was developed to simulate the grafting of monomers such as unsaturated carboxylic acids and silanes to ethylene polymers. The polymers considered were ethylene-co-vinyl acetate (EVA), ethylene-co-butyl acrylate (EBA), and low-density polyethylene (LDPE). Grafting was assumed to proceed by a free-radical mechanism involving chain transfer. Organic peroxides having a strong tendency for hydrogen abstraction were selected as the source of primary radicals. The model simulated the grafting reaction as taking place in a single screw extruder. The residence time distribution in the extruder was experimentally determined by tracer analysis, according to which the extruder was a plug-flow reactor connected to two mixed reactors in parallel. The model is able to predict the extent of grafting in terms of predefined parameters. Comparison of model predictions with available experimental data showed slight deviations, the possible causes of which are discussed. However, the kinetic behavior expected on the basis of the input parameters was observed, and, as such, the model allowed study of the effect of process variables on grafting kinetics and provided insight into the reaction mechanism.
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  • 83
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    Polymer Engineering and Science 29 (1989), S. 1611-1613 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Using an energy balance approach incorporating a Flory-Huggins expression for free energy and the strain energy of the material, the solvent removal process in liquid-based coatings was shown to depend on stress and temperature. An equilibrium is obtained between residual solvent content and stress in the coating at a given temperature. Such stress-dependent solvent removal behavior was observed with a polyamic acid coating solution-cast using N-methylpyrrolidinone.
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  • 84
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    Polymer Engineering and Science 29 (1989), S. 1628-1635 
    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 compressive and tensile properties of polyester mortar were studied under various curing conditions, temperature, and strain rate. The curing temperature was varied from room temperature to 80°C. The behavior of polyester mortar was studied using a uniform sand with strain rate and temperature varied between 0.01 to 6 percent strain per minute and 22°C and 120°C, respectively. The strength, failure strain, modulus and stress-strain relationships of polyester mortar are influenced by the curing method, testing temperature, and strain rate to varying degrees. The influence of test variables on the mechanical properties of polyester mortar are quantified. Pretreating the aggregates with a silane coupling agent further enhances the compressive and tensile strength of the mortar. The compressive modulus and splitting tensile strength of polyester mortar are related to the compressive strength. A constitutive model is used to predict the compressive stress-strain behavior of polyester mortar.
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  • 85
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    Polymer Engineering and Science 29 (1989), S. 1638-1641 
    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: Die-drawing techniques recently developed at Leeds University make it possible to produce oriented polymer tubes with both axial draw and hoopwise expansion. These products have increased axial stiffness, improved barrier properties, and excellent resistance to chemical reagents. Normally mechanical methods are used to join such tubes in order to preserve their orientation: however we show that electrofusion techniques produce joints of strengths such that in tensile tests, failure always occurs in the fittings, not at the joint interfaces. Optical and electron microscopy reveal different zones in the welds and indicate that only 20 percent of the wall thickness is affected by the electrofusion process. The pipe studied was biaxially drawn medium density polyethylene of outside diameter 63 mm with draw ratios of 4 in the axial direction and 2, inner hoop. Optimum welding conditions were determined using socket and saddle electrofusion fittings. The joints did not fail in a standard crush test. Careful control of welding parameters is essential in butt fusion welding when the maximum weld strength exceeds that of the undrawn polymer.
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  • 86
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    Polymer Engineering and Science 29 (1989), S. 1655-1660 
    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: Short welding times make spin welding particularly suitable for mass production. This paper presents an analysis of the friction phase, which makes it possible to estimate the influence of the welding parameters and the material being welded on the temperature in the welded zone, the melt rate, and the torque in the spin welding of semicrystalline thermoplastics. A comparison of experimental and calculated results shows an acceptable correlation. In addition, the influence of speed, axial pressure, and braking on the weld seam quality of different amorphous and semicrystalline thermoplastics is discussed.
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  • 87
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    Polymer Engineering and Science 29 (1989), S. 1683-1688 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. Past work on welding characterized the effects of weld parameters such as the weld frequency, the weld pressure, and the weld time, on the welding process and weld strength, and showed that the most important parameter affecting weld strength Is the weld penetration - the decrease in the distance between the parts being welded that is caused by lateral outflow of material in the molten film. However, those weld studies were based on specimens of constant nominal thickness (6.35 mm, 0.25 in). This paper is concerned with the effects of specimen thickness on the weld process and weld strength.
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  • 88
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    Polymer Engineering and Science 29 (1989), S. 1689-1698 
    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: Ultrasonic welding is one of the most popular techniques for joining thermoplastics because it is fast, economical, and easily automated. In near-field ultrasonic welding, the distance between the horn and the joint interface is 6 mm or less. This study investigated the near-field ultrasonic welding of amorphous (acrylonitrile-butadiene-styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. High frequency ultrasonic wave propagation and attenuation measurements were made in order to estimate the dynamic mechanical moduli of the polymers. The estimated moduli were entered into a lumped parameter model in order to predict heating rates and energy dissipation. Experimental results showed that variations in the welding pressure had little effect on energy dissipation or joint strength; Increasing the amplitude of vibration increased the energy dissipation and the weld strength. For the semicrystalline polymers, increasing the weld time improved strength up to weld times greater than 1.5 s, where strength leveled off. For the amorphous polymers, the weld strength increased with Increasing weld time up to times of 0.8 s; for longer weld times, the power required was too high, causing overloading of the welder. Monitoring of the energy dissipation and static displacement or collapse provided valuable information on weld quality.
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  • 89
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    Polymer Engineering and Science 29 (1989) 
    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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  • 90
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    Polymer Engineering and Science 29 (1989), S. 1733-1737 
    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 hydrolytic stability of a new commercial polycarbonate (Calibre 300, Dow Chemical USA) was investigated and compared with that of other commercial polycarbonates. The tests were conducted between 56% and 95% relative humidity (R. H.) at 100°C. Also performed were water immersion tests at 80 and 100°C. The water diffusivity was found to be 8.7 × 10-7 cm2/s at 100°C with an activation energy of 7.9 kcal/mole. These values are similar to other glassy polymers. The equilibrium water sorption, C∞, was found to increase with temperature and R.H. The isotherm at 100°C was determined to be: C∞ = 0.005945 [R.H.]. When samples immersed in a water bath at 100°C were transferred into room-temperature water, visible aqueous microcavities were formed due to the condition of super-saturation, and under stress may become crack initiation sites. For the polycarbonate investigated here, it was found that the decrease in weight-average molecular weight (M̄)w was a first-order process under a constant R.H. and temperature, and that hydrolytic embrittlement, i. e., (M̄)w 〈34,000, was reached after ca. 188, 143, 99, and 66 days under 56%, 73%, 87%, and 95% R.H., respectively, at 100°C. A comparison with reported hydrolytic stability data for other polycarbonates showed large differences in their stability which are believed to be due to the extent of end-group capping (over 95% in Calibre 300) and resin purity: both phenolic end-groups and some additives (i.e., fire retardants, thermal stabilizers) are known to accelerate hydrolytic degradation.
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  • 91
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    Polymer Engineering and Science 29 (1989), S. 1766-1773 
    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: Moldability and mechanical properties of polyethylene terephthalate (PET) under normal molding conditions were found to improve significantly when it was blended with bisphenol-A-polycarbonate (PC) and polypropylene (PP) to form ternary polymer blend systems. DSC results of these blends revealed that the PET and PC components formed a miscible blend while PP being incompatible with them, formed a separate phase. PP was also found to form a sleeve around the PET-PC miscible phase and, thereby, showed a skin-core type of morphology. Variations of mechanical properties with varying amounts of PP was measured keeping the ratio of PET and PC constant. Tensile and flexural properties of the blends decrease with the amount of PP. Notched impact strength increases up to a certain level of PP and then decreases, while the unnotched values decrease gradually. The effect of annealing on the mechanical properties of these blends have been discussed on the basis of the increased crystallinity of some of the components.
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  • 92
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    Polymer Engineering and Science 29 (1989), S. 29-35 
    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 analytical technique, modulus profiling, conveniently allows the mechanical properties of elastomers to be mapped with spatial resclutions approaching 0.05 mm. Thus, spatial heterogeneities in modulus caused by processing and aging phenomena can be easily monitored. This paper describes some typical results from polymer aging studies, which Indicate the insights available from this technique. These include application of modulus profiling to understanding (1) mechanical property deterioration of Viton in an elevated temperature, gamma-radiation environment, (2) recent continuous stress-relaxation results, and (3) the role of ozone for non mechanically-stressed materials in high energy radiation environments.
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  • 93
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    Polymer Engineering and Science 29 (1989), S. 36-43 
    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 polymeric molecular weight and molecular weight distribution on pressure-sensitive adhesive performance was studied in a model system of commercial polyisobutylenes. Molecular weight was characterized by size exclusion chromatography and membrane osmometry. Pressure sensitive adhesive performance was assessed by shear, peel, and probe tack testing based on standardized test methods. Lower molecular weight polyisobutylenes (Mw 〈 600,000) are successful in peel and probe tack testing due to their ability to flow quickly and wet the substrate test surface. They do not function as well in shear, however, where the polymer must resist flow under a load. High molecular weight species, by contrast, perform well in shear resistance tests and less successfully in peel and probe tack testing. Where high and low molecular weight polyisobutylenes are blended to broaden the molecular weight distribution while maintaining constant weight average molecular weight, adhesive performance in shear, peel, and probe tack are improved. All of the adhesive properties tested were found to have their foundation in some fundamental rheological properties of the polymers (e.g., shear viscosity and tensile creep compliance). This suggests the use of fundamental rheological characterization for screening of adhesive formulations over more empirical adhesive testing methods.
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  • 94
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    Polymer Engineering and Science 29 (1989), S. 44-54 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Poly[1-(trimethylsilyl)propyne] (PTMSP) is an unusual polyyne material which is optically clear, exhibits high solubility in nonpolar organic solvents, and good oxygen compatibility. By contrast, polyacetylene is black, insoluble, and is unstable in oxygen. The long term stability of PTMSP has been determined by a combination of thermal gravimetric analysis (TGA) and permeability test procedures under a number of different isothermal aging conditions. The use of commercial antioxidants at up to 2 weight percent improves the long term stability of PTMSP. The presence of the antioxidant has no effect on the surface fluorination of PTMSP. Testing of PTMSP films for over eight months shows no change in either permeability or selectivity in contrast to previously reported data.
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  • 95
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    Polymer Engineering and Science 29 (1989), S. 120-126 
    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 conservation equations of momentum, energy, and mass are numerically solved for the flow of filled thermosets reacting In a tube. The flow is assumed to be laminar and adiabatic with a constant volumetric flow rate. The critical radii are parameters that define the processability limits. The lower one is the value of the radius where an undesirable advance in the reaction extent takes place at the wall or where viscous heating leads to degradation. The upper critical radius is the radius where wall velocity is low and gelation takes place. The effects of filler volumetric fraction, wall slip velocity, and different inlet conditions are taken into account. Increasing wall slip velocity or filler fraction and decreasing inlet temperature or tube length amplify the processability zone.
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  • 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
    Notes: A series of polyimides based on 4.,4′-isophthaloyldiphthalic anhydride (IDPA) was prepared and characterized by inherent viscosity, differential scanning calorimetry (DSC), solubility, wide-angle X-ray scattering (WAXS), and isothermal thermogravimetric analysis (ITGA). Film forming, tough, insoluble polyimides were obtained with most of the 11 diamines used for evaluation. Two materials were semicrystalline. Several compositions showed excellent thermooxidative stability by ITGA at 300 and 350°C in air, as compared to Kapton-H (Du Pont) film. The IDPA-m-phenylenediamine (m-PDA) composition, for example, gave a flexible, amorphous film having a Tg of 259°C (identical with LARC-TPI) and insoluble in a wide range of solvents. It is based on a potentially low-cost dianhydride (IDPA) and, unlike LARC-TPI, a low-cost, domestically available diamine which gives a negative Ames test.
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  • 97
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    Polymer Engineering and Science 29 (1989) 
    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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  • 98
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    Polymer Engineering and Science 29 (1989), S. 178-185 
    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 of polymer soluticn devolatilization in a counterrotating twin-screw extruder has been undertaken. In an effort to ultimately predict mass transfer rates in such a process, this work analyzes the experimental results to determine the controlling mechanisms in the separation of volatile components from the polymer. The devolatilization process at hand encompasses the heavily foaming and nonfoaming regimes. Historically, the literature has centered primarily around the highly concentrated, bubble-free diffusion-controlled devolatilization regime. The analysis presented in this paper centers on the performance of the heavily foaming stages of the process. Recent and previously reported (1) data on the polystyrene/ethylbenzene (PS/EB) system, as well as newly collected data on the poly(methyl methacrylate)/methyl methacrylate (PMMA/MMA) system, are analyzed. In the foaming stages of the process, two regimes have been found. These regimes are differentiated by the availability of volume into which the foam can grow. Deformation and mixing effects appear to be secondary. Furthermore, temperature changes across the range of realistic operating conditions appear to affect mainly the thermodynamic driving force. It is only at extremely high temperatures that these effects are truly controlling.
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  • 99
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    Polymer Engineering and Science 29 (1989), S. 193-201 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In the first part of this series, the influence of mold geometry was examined with reference to the improvement of the mechanical properties of elongational flow injection-molded polyethylene. In the present study (Part 2), processing parameters have been investigated and the physical properties of the moldings examined. It is confirmed that mainly two parameters, the temperature of the melt and the pressure on the solidifying mold, govern the injection process. Results are discussed in terms of the molecular orientation that is developed during the filling process and depends on the temperature of the melt. The application of high pressures leads to a pressure-induced crystallization effect that freezes in the molecular orientation within the mold.
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  • 100
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    Polymer Engineering and Science 29 (1989), S. 202-208 
    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 thermocouple ring-bar device located between the nozzle and screw-tip was used to study the thermal homogeneity of a shot formed during injection molding. Axial and radial melt temperature profiles thus observed under various processing conditions illustrated the importance of screw channel volume-to-short-size ratio on melt homogeneity, Several methods of improving melt quality, as measured by this device, are demonstrated.
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