Two Stages in the Process of Network Formation in Polymers

Abstract 1. The two-stage nature of network formation in polymers is discussed, and a formula is derived connecting the number of chains in the network with the initial molecular weight of the polymer and the number of crosslinks. It is shown that below a certain critical number of crosslinks a network is not formed. 2. The application of the derived relationships in determination of the number of sulfur atoms in the crosslinks, the critical molecular weight, and the degree of globulization of the rubber, has been studied in the case of rubber vulcanization. 3. The first vulcanization stage is shown to be of considerable practical importance, as it determines the correct technological conditions for the vulcanization of rubber in molding presses, multilayer articles, etc. For this reason, determinations of the vulcanization optimum in rubber technology must be augmented by studies of the initial stage of the process. A method for determining the duration of the first stage of vulcanization is described.