Glass fiber/epoxy composites with improved interfacial adhesion by using cross-linking sizing agent

Glass fibers (GFs) are frequently employed as reinforcement fibers for polymer resins such as epoxy and polyester. The mechanical behaviors of GFs polymer composites are nevertheless constrained by weak interfacial adhesion between polymer matrix and GFs. Herein, we invented a cross-linking modified sizing agent using polyethyleneimine and bisphenol A epoxy emulsion, and studied the effect of cross-linking extent on GF surface characteristics and GF/epoxy interfacial adhesion. The treatment of GFs with cross-linking modified sizing agent facilitated the formation of interpenetrating polymer networks in composites for strengthening interface interaction. The results show that the modified GFs have a rough surface and improved interfacial adhesion with epoxy matrix. When sizing agents with cross-linking extent of the 23.0%, the GF/epoxy composites show advanced interfacial shear strength (IFSS) and transverse fiber bundle tension (TFBT) strength. This work demonstrates that the cross-linking extent of sizing agent could regulate interfacial adhesion, which is a facile and promising strategy in reinforcing glass fiber polymer composites. Highlights: Crosslink the sizing agent to enhance GF mechanical properties was reported. GF surface energy was enhanced and thickness of GF/epoxy interphase increased. IFSS and TFBT strength of the GF/resin composites increased by 23.65% and 30.54%, respectively.