Quiz9Sp02 - 2) ENSC 3313, Spring 2002 Quiz 9 Name Answer...

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2) Quiz 9 Name ENSC 3313, Spring 2002 Answer any 4 Questions only, 1 point each .1. How many kg of S are needed to cross link 6% of the sites in 2500 kg of polyisoprene? Assume the S is 40% efficient. Isoprene is CSH8. The amu of S = 32. To completely cross link, 2 ofS link 2 mers ofisoprene. Isoprene is CsHs. Hence, need 32 kg ofS to com~letely cross link 68 kg of isoprene at 100% efficiency. Thus, need 2500 x 32 x 0.06 kg ofS to cross link 6% of the sites of2500 kg of isoprene -1Q kg. 68 But, s is 40% efficient, so need 70 -l1Q kg. 0.4 Explain the following with respect to polymers. 2. a) plasticizers A small stable high boiling point organic molecule added to a polymer to lower its glass transition temperature. It fits between chains so facilities chain sliding. It is used in vinyls, for example. b) polydispersivity index PDI -Mm /Mn ---the ratio of mass average to number average molecular weight. It is a measure of the ~formity of polymerization. c)
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Quiz9Sp02 - 2) ENSC 3313, Spring 2002 Quiz 9 Name Answer...

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