Micro-roughening of polyamide fabric using protease enzyme for improving adhesion strength of rubber-polyamide composite

The adhesion between rubber and the reinforcing textile plays an important role in ensuring the serviceability of composites. The present study aims to develop an enzyme based surface roughening process for nylon 6,6 fabric to improve its adhesion strength to rubber. Polyamide (nylon 6,6) fabric was micro-roughened through catalysed hydrolytic degradation of the surface chains, using a protease enzyme treatment. The concentration of the enzyme was optimized in terms of surface roughness measured by a KES-FB4 surface tester. Scanning electron microscopy (SEM) images of the protease treated fabric showed a heterogeneous rough appearance with cracks and pits. Fourier transform infrared (FTIR) analysis confirmed the surface hydrolysis of polyamide-6,6 due to the enzymatic treatment. Protease enzyme treated fabrics were then subjected to resorcinol formaldehyde latex (RFL) treatment, followed by a rubber moulding. Micro-roughening of nylon 6,6 fibre with an optimum surface roughness (SMD) of 20.3 mu m was obtained for 3% enzyme concentration. Physicochemical mechanisms of the optimum effect and enzyme assisted hydrolysis were proposed. In line with surface roughness, peel strength also increased up to an enzyme concentration of 3% and then it decreased, however, the enzyme treated fabric showed higher peel strength than the control fabric.