Network structure and reaction mechanisms in high pressure and peroxide vulcanization of polybutadiene: Microstructural changes studied by C-13 solid-state NMR

This article is concerned with the microstructural changes during peroxide and high pressure vulcanization of polybutadiene that is unfilled and fille d with carbon black. The main tool is C-13 solid-state NMR; it shows that v inyl unsaturations are consumed in both filled and unfilled samples under p eroxide and high pressure vulcanization. Chemical shift calculations of unv ulcanized polybutadiene show good agreement with the observed peaks. Calcul ations of proposed structures, based on a possible reaction mechanism, sugg est that a large number of peaks will appear, each at very low intensity. N evertheless, some changes can be seen as a result of the crosslinking react ion, and the results provide support for the suggested reaction mechanism. Thus, the proposed addition crosslinking mechanism over vinyl unsaturations seems to be a reasonable explanation of the crosslink formation in high pr essure vulcanization. (C) 1999 John Wiley & Sons, Inc.