   # Engineering Materials Week 10

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Topics: Polymer
Engineering Materials Week 10
14.4 (a) Compute the repeat molecular weight of polypropylene.

(b) Compute the number average molecular weight for a polypropylene for which the degree of polymerization is 15,000.

14.10 Using the definitions for total chain molecule length L and average chain end-to-end distance r, for a linear polytetrafluroethylene determine: (a) the number average molecular weight for L=2000 nm. (b) the number–average molecular weight for r=15 nm. 14.19 (a) Determine the ratio of butadiene to acrylonitrile repeat units in a copolymer having a number-average molecular weight of 250,000 g/mol and a degree of polymerization of 4640.

(b) Which type(s) of copolymer(s) will this copolymer be, considering the following possibilities: random, alternating, graft and block? Why?
On the basis of the result in part (a), the possibilities for this copolymer are random, graft, and block.
14.23 For each of the following pairs of polymers, do the following: (1) state whether or not it is possible to determine whether one polymer is more likely to crystallize than the other, (2) if it is possible, note which is then more likely and then cite reason(s) for your choice; and (3) if it is not possible to decide, then state why. (a) Linear and atactic poly (vinyl chloride); linear and isotactic polypropylene.
No, it is not possible to decide for these two polymers. The isotactic PP is more likely to crystallize than the atactic PVC.
(b) Linear and syndiotactic polypropylene; crosslinked cis-isoprene.
Yes, it is possible to decide for these two copolymers. The linear and syndiotactic polypropylene is more likely to crystallize since linear polymers are more likely to crystallize than crosslinked ones.
(c) Network phenol-formaldehyde; linear and isotactic polystyrene.
Yes, it is possible to decide for these two polymers. The linear and isotactic polystyrene is more likely to crystallize than network phenol-formaldehyde.
(d) Block poly (acrylonitrile-isoprene)

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