Adhesion and friction behavior between fluorinated carbon fibers and poly (vinylidene fluoride)

Abstract

The potential use of fluorinated, polyacrylonirtile-based, high strength carbon fibers as reinforcement for a fluorocarbon polymer, namely poly (vinylidene fluoride) (PVDF), was investigated by means of the single fiber pull-out test. The apparent interfacial shear strength as a measure of practical adhesion was determined and the fracture and friction behavior of the model composites characterized. It was shown that the fracture behavior of the model composites is predominately brittle in nearly all cases. Fluorination of carbon fibers has a positive impact on the adhesive strength to PVDF. The apparent interfacial shear strength increases with increasing degree of fiber surface fluorination and becomes maximal at a degree of fiber fluorination (F/C-ratio) of around 0.8, determined by ESCA, which is close to that of PVDF. This result points to the fact that the increased “practical” adhesion is due to a physical compatibilization between the fluorinated fibers and the surrounding PVDF matrix. It was found that, even though the interfacial shear strength increases with increasing degree of fiber surface fluorination, the friction between fluorinated carbon fibers and the surrounding PVDF decreases.