Anisotropy of Rubber Networks Crosslinked in States of Strain

Abstract

Anisotropy of amorphous polymer networks crosslinked first in the isotropic state and subsequently in the stretched state is analyzed using the junction constraint theory. According to the theory, the anisotropy results from the anisotropy of elastic constraint domains trapped in the network structure during the two stages of crosslinking. The calculated differences in elastic moduli parallel and perpendicular to the direction of stretch during crosslinking are observed to compare favourably with experimental data on natural rubber and poly(ethylacrylate) networks. The theory also predicts a small anisotropy in swelling where the linear dilation along the parallel direction to crosslinking differs from those in the lateral directions.