Reclamation of vulcanized rubbers by chemical degradation. V. Degradation of vulcanized synthetic isoprene rubber by the phenylhydrazine–ferrous chloride system

The changes of effective network chain density and soluble fraction were measured for gum vulcanizates of synthetic isoprene rubber (IR) during the degradation by the phenylhydrazine–ferrous chloride system. From the decrease of effective network chain density and the increase of soluble fraction, the network chain was concluded to undergo a severance reaction by the reagents in the following order of ease: polysulfide linkage > monosulfide linkage > carbon–carbon crosslink. Analysis of the relation of soluble fraction with decrease of effective network chain density according to the theory of Horikx indicated that the severance of crosslinks predominated over main‐chain scission in the degradation of sulfur vulcanizate by the reagents. The experiments of the degradation of sulfur vulcanizate in sealed vessels in the absence of oxygen indicated that atmospheric oxygen is necessary for the degradation reaction.