Interfacial polycondensation of nylon-6,6 at the glass fibre surface and its effect on fibre–matrix adhesion

The surface of glass fibres was modified using chemical treatments to improve fibre–matrix interface properties. Interfacial polycondensation was performed with the fibre acting as the interface, and nylon-6,6 chains were grafted on the free hydroxyl groups located at the fibre surface. Grafted nylon was observed through the scanning electron microscope. The effect of the treatment on the fibre-matrix adhesion was investigated by measuring the interfacial shear strength in fragmentation micromechanical tests. The two-parameter Weibull distribution was used to analyse the experimental results. Polarized optical microscopy showed the existence of a transcrystalline layer in treated samples, indicating better fibre wettability by the matrix. Scanning electron microscopy confirmed the presence of an excellent bonding between fibre and matrix in treated samples, whereas in untreated samples, fibre pull-out was predominant, indicating poorer fibre–matrix adhesion.