Chapter 15.6

Chapter 15.6 - ± Significantly slower than addition...

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27 MSE 2090: Introduction to Materials Science Chapter 15, Processing of Polymers Elastomers: Vulcanization (II) ¾ Because they are cross-linked, elastomeric materials are thermosetting polymers ¾ Elastic modulus, tensile strength, oxidation resistance increased by vulcanization - magnitude of E proportional to number of cross-links. Too many cross-links reduces extensibility
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28 MSE 2090: Introduction to Materials Science Chapter 15, Processing of Polymers Polymerization 1. Addition (chain-reaction) polymerization , where monomer units are attached one at a time (discussed in Chapter 14). Has three distinct stages: initiation, propagation, and termination. 2. Condensation (step reaction) polymerization , by stepwise intermolecular chemical reactions that produce the mer units. ± Usually there is small by-product that is then eliminated
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Unformatted text preview: ± Significantly slower than addition polymerization ± Often form trifunctional molecules that can form cross-linked and network polymers Polymerization is the synthesis of high polymers from raw materials like oil or coal. It may occur by: 29 MSE 2090: Introduction to Materials Science Chapter 15, Processing of Polymers Summary ¾ Addition polymerization ¾ Condensation polymerization ¾ Crazing ¾ Creep modulus ¾ Deformation of semicrystalline polymers ¾ Effect of molecular weight, crosslinks, drawing, degree of crystallinity on mechanical properties ¾ Elastomer ¾ Fracture of polymers ¾ Glass transition temperature ¾ Plastics ¾ Relaxation modulus ¾ Thermoplastic polymer ¾ Thermosetting polymer ¾ Viscoelasticity ¾ Vulcanization Make sure you understand language and concepts:...
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This note was uploaded on 02/14/2012 for the course MSE 2090 taught by Professor Leoindzhiglei during the Fall '10 term at UVA.

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Chapter 15.6 - ± Significantly slower than addition...

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