Abstract

Four different samples of cow softy leather (designated CSAS0, CSAS1, CSAS2, and CSAS3) were prepared from a chrome-tanned cow wet-blue of Indian origin. CSAS0 was the control sample wherein no polyacrylate based syntan was added. CSAS1, CSAS2, and CSAS3 contain different polyacrylate based syntans (3% w/w), differing in molecular weight, in addition to the other common auxiliaries used in all of the four samples. Other unit operations (physical and chemical) for manufacturing leather were the same in all the samples. Thermal, mechanical, and solvent swelling behaviour of these four samples were studied and we attempted to correlate them with the cross-linking densities of the samples. The swelling behaviour was studied in five different solvents (e.g. water, toluene, xylene, methyl ethyl ketone (MEK), and acetone), assuming definite solvent-bovine collagen interaction parameters and respective cross link densities were evaluated by the Flory-Rehner equation. While studying the mechanical behaviour, some distinguished theoretical models (e.g. Mooney-Rivlin, Flory, and Martin, Roth & Stiehler (MRS)) were tried to fit with the experimental results obtained during stress-stain analyses. In this process a few constants for cow Cr-tanned leather were derived as values of constant A in MRS equation remained in the range of 0.9-1.0, and value of constant B in Floryʼs equation remained in the range of 0.001-0.005, which had not been reported in the literature. The experimental results showed that the polyacrylate based syntan, bearing a higher level of free acrylic acid groups or a fewer proportion of esterified acrylic acid groups, formed better cross links with chrome-tanned bovine leather in comparison to other polyacrylate based syntans containing higher proportions of esterified acrylic acid groups. Moreover, high molecular weight polyacrylate based syntans provided better thermal and solvent resistance in comparison to low molecular weight polyacrylate based syntans.