lecture_9_-_polymers_-_chapter_8

lecture_9_-_polymers_-_chapter_8 - ME 350 Lecture 9 Ch 8...

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ME 350 – Lecture 9 – Ch 8 Natural Rubber Nylon (replaces silk) PVC Kevlar (replaces metal alloys) HDPE (replaces cast iron, Cu)
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Polymers Polymers are described as plastics and rubbers Three categories: 1. Thermoplastic polymers 2. Thermosetting polymers 3. Elastomers Which are plastics? Which are rubbers? # 3
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Thermoplastic Polymers - Thermoplastics Solid materials at room temperature but viscous liquids when heated Can be easily and economically shaped into products Can be subjected to heating and cooling cycles without significant degradation: repeatedly Symbolized by TP
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Thermosetting Polymers - Thermosets Cannot tolerate repeated heating cycles When initially heated, they soften and flow for molding Elevated temperatures produce: a chemical reaction that hardens the material into an infusible solid If reheated, rather than soften, thermosets: degrade and char Symbolized by TS
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Elastomers (Rubbers) Polymers that exhibit extreme elastic extensibility Some elastomers can be stretched by a factor of 10 and yet completely recover to their original shape. What would its EL% be? 900% Although their properties are quite different from thermosets, they share with thermosets a similar: molecular structure
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Polymer Notation MW of one monomer? C (12) = 24 H (1) = 3 Cl (36) = 36 MW = 63
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Polymerization Addition polymerization Model of addition (chain) polymerization: (1) initiation, (2) rapid addition of monomers, and (3) resulting long chain polymer molecule with n mers at termination of reaction
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This note was uploaded on 10/03/2011 for the course ME 350 taught by Professor Staff during the Spring '08 term at University of Illinois, Urbana Champaign.

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lecture_9_-_polymers_-_chapter_8 - ME 350 Lecture 9 Ch 8...

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