Microdebond test development and interfacial shear strength evaluation of basalt and glass fibre reinforced polypropylene composites

Interfacial adhesion of basalt and glass fibre reinforced polypropylene composites was studied using microdebond testing technique. A focus was put on a simple approach of applying extruded thermoplastic films as a matrix material for microdroplet formation. The ability of different viscosity and thickness polypropylene films to form symmetrical droplets under a temperature range of 200–240℃ was evaluated. Emphasis was put on polypropylene matrix chemistry, silane fibre surface treatment and testing loading rate impact on interfacial performance change in polypropylene-basalt fibre and polypropylene-glass fibre microcomposites. It was found that it was possible to obtain high symmetrical droplet yield out of polypropylene films of melt flow rate 50 and 125 g/10 min and 55–85 µm thickness at 240℃. The presence of maleic anhydride grafted polypropylene coupling agent increased the interfacial shear strength significantly. Microcomposites with glass fibre had higher interfacial shear strength in comparison with the used basalt fibre, mainly due to the difference in their sizing. Various silane-based fibre surface coatings did not result in significant interfacial adhesion changes. Polypropylene-glass fibre microcomposite interfacial shear strength at 0.5, 3.0 and 10.0 mm min–1 loading rates had similar values with high maximum pull-out force scatter at 0.5 and 3.0 mm min–1 loading rates and low scatter at 10.0 mm min–1.