Quiz9spr2004 - ENSC 3313, Spring 2003 Quiz 9 ANSWERS Name_...

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ENSC 3313, Spring 2003 Quiz 9 ANSWERS Name ________________________________ Answer any 4 questions only , 1 point each 1. Define the following with respect to polymers: thermoplastic – a polymer that softens when heated and hardens upon cooling. syndiotacic – a type of polymer chain configuration in which side groups regularly alternate positions on opposite sides of the chain polydispersity index – PDI = N W M M ; a measure of the uniformity of polymer chain length. Closer to unity means more uniform chain length. glass transition temperature – T g ; the temperature below which chain sliding is inhibited and the polymer behaves like a brittle glass, i.e., purely elastic with brittle fracture. 2. The polyethylene mer has a bond length of 0.26 nm. Calculate the average chain length of an ultrahigh molecular weight polyethylene with mol g M W / 10 4 6 × = . Note: mer wt. = 28 g/mol; assume the polymer is linear. The weight average degree of polymerization is:
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Quiz9spr2004 - ENSC 3313, Spring 2003 Quiz 9 ANSWERS Name_...

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