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  • 1
    Electronic Resource
    Electronic Resource
    Deep drawability of biaxially rolled thermoplastic sheets (1972)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 12 (1972), S. 150-156 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The deep drawability of biaxially cold-rolled thermoplastic sheets has been studied using polycarbonate, polyvinyl chloride, and acrylonitrile-butadiene-styrene polymers. Each polymer was rolled to two different reductions in thickness. The deep drawability of these rolled sheets was measured by determining the limiting draw ratio using a Swift cup test. Strain ratios were measured in three directions for each of the rolled sheets in order to determine the normal and planar anisotropy of the sheets. It has been determined that the drawability of a sheet can be correlated with the normal anisotropy of the sheet and it is the increase in normal anisotropy of a sheet which increases the drawability of the sheet. It has also been shown that lubrication increases the drawability due to a reduction in punch force.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760120212
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  • 2
    Electronic Resource
    Electronic Resource
    High pressure non-isothermal processing, of linear polyethylenesPresented at the 33rd ANTEC, Atlanta, Georgia, May 5-8, 1975. (1976)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 16 (1976), S. 15-24 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Articles with increased rigidity can be obtained by compression molding at high pressures as shown by experiments with five types of linear polyethylene. The materials, with weight average molecular weight ranging up to 1,000,000 were molded at pressures as high as 80,000 psi. The material temperature was 149-204°C, and the tooling was at 38°C. The duration of load was typically 3 mins, and the thickness of the molded disks was 12.7 mm. The results show that at high molding pressure the tensile modulus of the material is nearly twice that of materials molded conventionally at low pressures. This increase in modulus occurs for all the materials studied and even for a duration of load of only one min. The causes for this large increase in modulus were investigated with the help of density and melting point measurements and optical and electron microscopy. It was observed that the spherulites showed a distinctive and systematic change with the forming pressure. A hypothesis is proposed to explain the high modulus phenomenon on the basis of the kinetics of spherulite formation.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760160104
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  • 3
    Electronic Resource
    Electronic Resource
    Impact strength of polymers 2: The effect of cold working and residual stress in polycarbonates (1980)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 20 (1980), S. 756-762 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The influence of cold working on the toughness improvement in glassy amorphous polycarbonates was studied. Cold working processes, namely rolling and. Steckel rolling were used to produce thickness reductions up to 40 percent in flat-strip specimens. The notched Izod impact strength and tensile properties were measured as a function of strip thickness reduction. It was shown that the toughness enhancement in polycarbonates cold worked to low thickness reductions was due to the residual stress state present as opposed to molecular orientation which becomes significant at higher degrees of cold work. Residual stress measurements were made by using the layer removal technique. Residual tensile stresses as high as 2100 psi were present in 1/4-in. cold-rolled polycarbonate at the surface. The maximum stress in the center of the specimen was 1100 psi in compression. The residual stresses at the surface decreased with increasing thickness reduction. The residual stress state for Steckel rolled. 1/2-in. polycarbonate was also measured and found to be more complex than for the thinner samples, The results demonstrated that surface tensile stresses and interior compressive stresses can produce large values of impact strength if the notch is to be machined after cold working. Thus, the values of impact strength measured from the notch Izod specimen are sensitive to the residual stress state in the polymer. This behavior is in contrast to earlier studies on thermally quenched material in which the material was quenched after notching. The thermal quenching produced surface compressive stresses which were also present at the notch tip. The presence of compressive residual stresses at the center of the notch suppressed the formation of a craze leading to toughness enhancement in cold worked polycarbonate strips. It is shown that by control of residual stresses in polycarbonate, strips at least 1/2 in. in thickness can be made to exhibit ductile failure in the notched Izod impact test.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760201110
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