EFFECT OF SURFACE MODIFICATIONS OF LEATHER ON ITS JOINT STRENGTH WITHPOLYVINYL-CHLORIDE

The treatment of bovine leathers with wetting and lyotropic agents fol lowed by heating produced a strengthening of the leathers which increa sed their joint strength properties to polyvinyl chloride (PVC). A coh esive failure of leather was always obtained. The highest cohesive str ength (or point peel strength) was obtained when the treatment was car ried out at 140-degrees-C with the surfactant NFOE (8.5) (nonylphenol polyoxyethylene with 8.5 mol of oxyethylene). The lyotropic agents (Ca Cl2, urea) gave very high values (a five-fold increase), whereas the w ater-dimethyl ketone blends and pure water resulted in a smaller impro vement in cohesive strength (a three-fold increase). The improved cohe sive strength of leather was mainly due to the destruction of the orde red structure of collagen fibres and to the creation of a complex enta nglement network among the collagen fibres. The treatments applied to a bovine leather produced a shrinkage of 65%; the degree of shrinkage was not a function of the kind of treatment, but of the structure of t he leather. The application of surface treatments to leather prior to its bonding to other substrates may mean that the roughening process o f the leather, a tedious and difficult operation which is necessary in order to obtain adequate adhesive joints, can be avoided.