A study of dilation coefficients of cis-polybutadiene in simple extension

Force-pressure measurements at constant length and temperature have been made on a sample of crosslinked cis-polybutadiene in the range1·11<α<1·77 in order to determine values of the dilation coefficient $\text{(}\text{?}\text{ln}\text{V}\text{?}{}_{\mathrm{\alpha }}\text{)}{}_{\mathrm{P,T}}$. The results obtained, together with data reported earlier for natural rubber and butyl rubber, are compared with the predictions of (a) the Gaussian theory of rubber elasticity, and (b) a relationship based on the assumption that the linear compressibility is isotropic in extension.