Molecular Orientation of Rubber in Vulcanized Fillers-in Caused by Extension

Abstract

It is concluded from NMR, X-ray and other experimental results, that the rubber molecules of vulcanized fillers-in form three different phases, the unmotional, the collectively cross-linked, and the micro-Brownian motional, phase. And it is considered from the view point of molecular mobility that vulcanizates used as fillers-in form heterogenious structure. In the present experiment, we mixed a little amount of ZnO (needle-shaped crystals) in unvulcanized fillers-in, and made X-ray investigations of the orientation of ZnO atoms and the rubber crystals generated in the process of extension.
The results are as follows:
(1) The rubber molecules in the highly motional phase are quickly orientated by extension, but those of the unmotional and collectively cross-linked phases are slowly orientated to show non linear movement.
(2) Non linear movement of the unmotional phase is influenced greatly by the type of crosslink with sulfur; the less the number of sulfur atom in the sulfide cross-linkages, the less non linear character is.
This is attributed to the restraint of the movement of the rubber molecules in the unmotional phase due to the sulfide cross-linkages.