ME 477 Lecture Notes - Lecture 5: Thermosetting Polymer, Polyaniline, Polythiophene
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Plastics have less strength than metals but are much lighter. The electrical and thermal conductivity of metal is much higher than plastic. Finally, there is a signi cantly wider range of choices for color for plastics than metals: discuss the signi cance of the glass-transition temperature, tg, in engineering applications. The glass-transition temperature is the temperature where a thermoplastic behaves in a manner that is brittle, hard, and glassy below that temperature, and acts rubbery or leathery above that temperature. Thermoplastics begin to lose their load-carrying capacity above this temperature, so there is an upper useful temperature range for the plastic. Cross-linked polymers have additional bonds that link adjacent chains together. The strength is increased with thermoplastics because these cross links give additional resistance to material. Ow since they must be broken before the molecules can slide past each other.