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Unformatted text preview: Sheet1 Page 1 CH 4- STRUCTURES OF POLYMERS 2. (a) Compute the repeat unit molecular weight of polypropylene. (b) Compute the number-average molecular weight for a polypropylene for which the degree of polymerization is 15,000. A) For polypropylene, from Table 4.3, each repeat unit has three carbons and six hydrogens. m = 3(A_C) + 6(A_H) B) DP = M_n(m) so M_n = DP*m where m = 42.08 (m from A)) Err:510 3. Below, molecular weight data for a polytetrafluoroethylene material are tabulated. Compute (a) the number-average molecu A) Find mean M_i (ie avg molec wt range, [10+20]/2, and compute x_i*M_i. then M_n=sum(x_i*M_i). B) M_W = sum(w_i*M_i) C) m = 2(A_C) + 4(A_F) and DP = M_n/m Err:510 5. Molecular Shape A linear polyethylene has a number-average molecular weight of 300,000 g/mol m = 2(A_C)+4(A_H) = 28.05 and DP = M_n/m = 300,000/28.05 = # repeat units along avg chain. Since there are two carbon atoms per repeat unit, there are two C& C chain bonds per repeat unit, which means that the total...
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- Fall '07