Synthesis of a self-assembly amphiphilic sizing agent by RAFT polymerization for improving the interfacial compatibility of short glass fiber-reinforced polypropylene composites

Abstract This experimental study focuses on the development of an amphiphilic sizing agent to improve the interfacial adhesion and the mechanical properties of short glass fiber (GF)/polypropylene (PP) composites. To solve the critical compatible issue between the hydrophilic GF and the hydrophobic PP, we strategically utilized the reversible addition-fragmentation chain-transfer (RAFT) polymerization to self-assemble and synthesize an amphiphilic sizing agent. This surfactant-free sizing agent can create hydrogen bonds and electrostatic adsorption on GF surfaces and meanwhile can form molecular entanglements, alkyl cations, and σ-π conjugates with PP matrix. The FT-IR analysis shows that a large number of hydrogen bonds are formed on the sizing agent-GF interface. Additionally, the SEM micrographs of the composite fracture surfaces demonstrate strong interfacial compatibility between the sized-GF and the PP matrix. Comparing with the neat GF/PP composites, the tensile and flexural strength of the sized-GF/PP composites are increased by 25.8% and 33.1%, respectively. Their tensile strength and young's modulus are in close agreement to the analytical calculations. In short, this paper presents a new RAFT-based methodology to develop the amphiphilic sizing agents that are able to improve the interfacial compatibility of GF/PP composites and also can be transferred towards real applications for enhancing the mechanical properties of fiber-reinforced composites.