Interfacial Adhesion of Polyamide 66 Fibres to an Aqueous Polyurethane–Acrylic Hybrid Polymer Adhesive

In this work, the interfacial adhesion between a polyamide 66 fibre, and an aqueous polyurethane–acrylic hybrid polymer adhesive was investigated. Silane and air plasma treatments were introduced to modify the surface of the polyamide 66 fibre. The surface chemistry was characterised using X-ray photoelectron spectroscopy (XPS). There were more oxygen-containing functional groups, –OH or –COOH, introduced by air plasma and silane treatments on the surface of polyamide fibre to increase its chemical activity. The microbond test was used to measure the interfacial shear strength (IFSS) between the waterborne polyurethane–acrylic hybrid polymer adhesive and a polyamide fibre. It has been found that air plasma and silane surface treatments can be used to improve interfacial adhesion. IFSS at 8.7 and 5.9 MPa, respectively, were higher than that of the control, 5.0 MPa. After water immersion at 50°C for 48 h, IFSS dropped to 7.0 MPa for air plasma-treated specimen and to 4.4 and 4.1 MPa for silanised and control specimens, respectively. Air plasma surface treatment is more effective than silane treatment to improve the interface adhesion in the polymer fibre–polymer composite.