List the two molecular characteristics that are essential for elastomers.

 

1. List the two molecular characteristics that are essential for elastomers.

2. Which of the following would you expect to be elastomers and which thermosetting polymers at room temperature? Justify each choice.

(a) Epoxy having a network structure

(b) Lightly cross linked poly(styrene- butadiene) random copolymer that has a glass-transition temperature of −50°C

(c) Lightly branched and semicrystalline polytetrafluoroethylene that has a glass-transition temperature of −100°C

(d) Heavily cross linked poly(ethylene-propylene) random copolymer that has a glass-transition temperature of 0°C

(e) Thermoplastic elastomer that has a glass transition temperature of 75°C

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