Polypropylene, melting point radicals

Polypropylene made by free-radical polymerization is generally atactic , that is to say, there is no pattern to the stereochemistry. On the other hand, both isotactic polypropylene (in which all the stereocenters are the same) and syndiotactic polypropylene (in which the stereocenters alternate) may be made via the Ziegler-Natta process (see Chapter 18, Problem 4). Experimentally, both isotactic and syndiotactic polypropylene generally have higher melting points than atactic polypropylene. 

Oxidative Pyrolysis. Autoxidation of polypropylene below its melting point has been investigated quite thoroughly with our own laboratory among the most active ones (21, 22, 23,24). This is not the proper place to discuss that topic a chapter written by one of us dealing with the subject can be found in this volume. It suffices to say that the main chain propagating species is the peroxy radical and the chain branching species is the hydroperoxide. 

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