A comparative study of fibre/matrix interface in glass fibre reinforced polyvinylidene fluoride composites

Abstract

Due to the extreme chemical inertness and high thermal stability, fibre reinforced polyvinylidene fluoride (PVDF) composites have great potential for pipelines and vessels applications. In this study, surface properties of three differently sized glass fibres as well as a highly non-reactive thermoplastic PVDF and PVDF modified by maleic anhydride grafted PVDF (MAH-g-PVDF) 5ppm have been studied. A Wilhelmy method was used to characterise wettability of glass fibre and matrices, and estimate surface free energy and fibre diameter. In order to understand acidic/basic surface functionalities and the effect of dissociated functional groups on glass fibre surfaces, zeta-potential plateau values and the position of isoelectric points were recorded by zeta-potential measurements. The results of water contact angles and zeta-potentials for MAH-g-PVDF indicated that the concentration of the dissociated acid groups in the matrix bulk was increased by grafting maleic anhydride, but remained roughly constant on the surface.A single fibre pull-out technique was used for interfacial adhesion measurements. The results obtained for MAH-g-PVDF revealed the increased apparent interfacial shear strength by 135% and 75% for the acidic and basic surface fibre, respectively. No changes in interfacial shear strength in case of neutral surface glass fibre were observed. Therefore, better mechanical properties of composites can be achieved by improved interactions between acidic/basic surface glass fibre and MAH-g-PVDF matrix.