Enhancing the bond strength between glass fibre reinforced polyamide 6 and aluminium through μPlasma surface modification

Thermoplastic polymers generally exhibit relatively low surface energies and this often results in limited adhesion when bonded to other materials. Plasma surface modification offers the potential to functionalise the polymer surfaces, and thereby enhance the bond strength between dissimilar materials. In this study, glass fibre reinforced polyamide 6 (GFPA6) was modified using a novel μPlasma surface treatment technique and the effectiveness of the adhesive bond with aluminium was evaluated. The treated GFPA6 surfaces were characterised using atomic force microscopy (AFM), Raman spectroscopy, contact angle measurements, surface free energy calculations and wetting envelope analysis. The results show that there was a near exponential growth in root mean square roughness with increasing treatment scans. A significant increase in carbonyl and amide functionality on the polymer surface was observed using Raman spectroscopy. The total surface energy was found to increase from 42.2 mN/m to 67.6 mN/m following a single treatment scan. Significant increases in the tensile shear strength were observed up to 10 treatment scans, going from 1 kN to 2.3 kN, but no further increase was observed with additional treatment scans. These observations, coupled with the atmospheric nature of the technique, points to great potential as a rapid, on-line, and effective, polymer surface treatment technique.