Interfacial adhesion of recycled carbon fibers to polypropylene resin: Effect of superheated steam on the surface chemical state of carbon fiber

Abstract

The interfacial adhesion between polypropylene resin and recycled carbon fibers (RCFs) subjected to superheated steam (SHS) treatment was examined by performing microdroplet tests on the recovered single fibers. As-received virgin carbon fibers were selected as reference material for the evaluation. The interfacial shear strength (IFSS) was calculated to quantify the interfacial adhesion between the fiber and matrix. By comparing the IFSS of RCFs to those of corresponding virgin fibers, we found that 1 h SHS treatment at 650 °C improved the interfacial adhesion. X-ray photoelectron spectroscopy was employed to characterize the element composition and the content of functional groups on fiber surface. The SHS introduced extrinsic oxygen-containing functional groups on the fiber surface during the treatment. The increase in the IFSS value after SHS treatment is considered to be due to the chemical interaction at the interface between these functional groups and the resin.