(a) Is it possible to grind up and reuse phenolformaldehyde? Why or why not? (b) Is it possible to grind up and reuse polypropylene? Why or why not?

Compare thermoplastic and thermosetting polymers (a) on the basis of mechanical characteristics upon heating and (b) according to possible molecular structures.

For each of the following pairs of polymers, do the following: (1) State whether it is possible to determine whether one polymer is more likely to crystallize than the other; (2) if it is possible, note which is the 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 (b) Linear and syndiotactic polypropylene; crosslinked cis-polyisoprene (c) Network phenol-formaldehyde; linear and isotactic polystyrene (d) Block poly(acrylonitrile-isoprene) copolymer; graft poly(chloroprene-isobutylene) copolymer

Sketch cis and trans structures for (a) polybutadiene and (b) polychloroprene.

How do the densities compare for crystalline and amorphous polymers of the same material that have identical molecular weights? (A) Density of crystalline polymer < density of amorphous polymer (B) Density of crystalline polymer = density of amorphous polymer (C) Density of crystalline polymer > density of amorpous polymer