Interfacial Bonding between Different Elastomer Phases

A differential solvent-swelling technique was used to study the ability of different elastomers in a binary blend to covulcanize. The technique required that the two elastomer phases have sufficiently different solvent parameters so that one phase would be highly swollen while the other, below theta temperature conditions, would be lightly swollen. If interfacial bonds were present, a lightly swollen dispersed phase would restrict the swelling of a highly swollen continuous phase in a manner analogous to the restriction of swelling by reinforcing pigments. If interfacial bonds were absent, no restriction in swelling was observed. The presence or absence of interfacial bonds between chlorinated butyl rubber and polydiene rubbers depended on the type of curatives and crosslinking agents used. This suggested that certain types of chemical bonds as well as relative vulcanization rates were controlling factors.