Anisotropic swelling of rubber: extension of the Flory theory

Abstract

The anisotropy of the swelling of rubber is examined both theoretically and experimentally. The Flory theory is extended to account for anisotropic swelling, allowing the determination of the average molecular weight between cross-links for rubber with swelling anisotropy for the first time. In addition, specimens from five commercial rubbers manufactured using either compression-moulding or sheet-rolling processes are swollen in appropriate organic solvents. Their linear dimensions and mass are carefully recorded before swelling, in the swollen state, and after drying, to obtain three linear swelling ratios which can differ by up to 10% within each specimen. Compression-moulded rubbers are shown to be transversely isotropic after moulding, whereas rolled rubbers exhibit full anisotropy, with different swelling ratios in all three directions. None of the rubbers examined were found to be truly isotropic. The new anisotropic swelling theory is applied to the experimental data to determine the average molecular weight between cross-links, which is determined as up to 0.5% larger than the value obtained using the Flory isotropic swelling theory.

Thermodynamics of solvent sorption by layers of carbon-chain polymers in damping rubber blankets

“…The values of G E and S E presented in table 3 were calculated using equations (7) and (9). In equation (8), the calculated data in the coordinates lnγ 1…”

“…Swelling of composite sheets or layers made from five different commercial carbon-chain rubbers by pressing revealed the swelling anisotropy in organic solvents. Quantification of the swelling anisotropy, usinthe Flory's theory [6] allowed the authors [7] to determine the average molar mass of macromolecular carbon chains between crosslinks and obtain three linear swelling coefficients that differed by 10% within each sample. The swelling anisotropy of the layers of crosslinked carbon-chain polymers in the composition of layered blankets reinforced with fabrics is of a different physical nature.…”