Chapter 15: Problem 44
Contrast compression, injection, and transfer molding techniques that are used to form plastic materials.
Chapter 15: Problem 44
Contrast compression, injection, and transfer molding techniques that are used to form plastic materials.
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Get started for freeFor each of the following pairs of polymers, plot and label schematic stress- strain curves on the same graph [i.e., make separate plots for parts (a) to \((\mathrm{c})]\) (a) Polyisoprene having a number-average molecular weight of \(100,000 \mathrm{~g} / \mathrm{mol}\) and \(10 \%\) of available sites crosslinked; polyisoprene having a numberaverage molecular weight of \(100,000 \mathrm{~g} / \mathrm{mol}\) and \(20 \%\) of available sites crosslinked (b) Syndiotactic polypropylene having a weightaverage molecular weight of \(100,000 \mathrm{~g} / \mathrm{mol}\); atactic polypropylene having a weight- average molecular weight of \(75,000 \mathrm{~g} / \mathrm{mol}\) (c) Branched polyethylene having a numberaverage molecular weight of \(90,000 \mathrm{~g} / \mathrm{mol}\); heavily crosslinked polyethylene having a number- average molecular weight of \(90,000 \mathrm{~g} / \mathrm{mol}\)
Briefly explain how each of the following influ\(\Theta\) ences the tensile or yield strength of a semicrystalline polymer and why: (a) molecular weight (b) degree of crystallinity (c) deformation by drawing (d) annealing of an undeformed material
Why must fiber materials that are melt-spun and then drawn be thermoplastic? Cite two reasons.
For each of the following pairs of polymers, do ( the following: (1) State whether it is possible to decide whether one polymer has a higher tensile strength than the other; (2) if this is possible, note which has the higher tensile strength and cite the reason(s) for your choice; and (3) if it is not possible to decide, state why. (a) Linear and isotactic poly(vinyl chloride) with a weight-average molecular weight of \(100,000 \mathrm{~g} /\) mol; branched and atactic poly(vinyl chloride) having a weight-average molecular weight of \(75,000 \mathrm{~g} / \mathrm{mol}\) (b) Graft acrylonitrile-butadiene copolymer with \(10 \%\) of possible sites crosslinked; alternating acrylonitrile-butadiene copolymer with \(5 \%\) of possible sites crosslinked (c) Network polyester; lightly branched polytetrafluoroethylene
(a) Contrast the manner in which stress relaxation and viscoelastic creep tests are conducted. (b) For each of these tests, cite the experimental parameter of interest and how it is determined.
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