Elastic and thermoelastic behavior of cis‐polybutadiene crosslinked in the swollen state

Abstract

Samples of cis‐polybutadiene were cross‐linked in the presence of decalin at values of ϕr (the volume fraction of rubber) ranging from 0.25 to 0.50. After the diluent had been removed, a study was made of the force‐extension and thermoelastic behavior of the networks. Within experimental error, the ratio of the Mooney‐Rivlin constants 2C2/2C1 was found to be zero for networks prepared at low ϕr (0.25 and 0.30) but started to increase towards the conventional value at higher ϕr. The quantity fe/f was found to be independent of the ratio 2C2/2C1 and of the extension ratio α; the average value of fe/f was found to be 0.11.

Negative C2 values of inhomogeneous polymer networks measured in elongation

“…Lately, in some papers, a negative value of Cz also has been given for tensile measurements. [8][9][10] In this work, we were trying to find out for what other polymer networks it could be expected that the shape of the equilibrium stress-strain curve would lead to a negative CZ constant. We compared the tensile equilibrium deformation behavior of preswollen and swollen networks in water to equilibrium poly (2-hydroxyethyl methacrylate) (PHEMA) networks prepared by crosslinking copolymerization with ethyleneglycol dimethacrylate (cf.…”