Improving interfacial bonding strength between epoxy and PE-based wood plastic composites by micro-riveting

In this paper, we proposed a micro-riveting method using the wood fibers in the wood plastic composites (WPC) to effectively enhance the interfacial bonding strength between the epoxy coating and polyethylene (PE) -based WPC. The WPC surface with wood fibers partially embedded in the PE matrix was prepared using a simple solvent swelling and polishing method. Epoxidized Cardol having a long and hydrophobic chain was modified on the surface of the exposed wood fibers to improve the water-resistance and chemical reactivity of the wood fiber surface. Fourier transforms infrared (FT-IR) spectra, X-ray photoelectron spectroscopy (XPS), contact angle, confocal microscopy, and scanning electron microscope (SEM) have been used to characterize the composition and morphology of the surface structures. A pull-off test has been used to evaluate the interface bonding strength, which increased from 1.88 to 5.27 MPa. This constitutes the highest performance among all the non-plasma surface treatment reports (30 % higher than the highest bonding strength reported in the literature and comparable to plasma-based surface treatments). The epoxy-WPC interface showed excellent water resistance after immersing in sodium chloride (NaCl) solution (3.5 wt%) for 60 days. The proposed micro-riveting method is of high significance for WPC and may contribute to the interface adhesion enhancement of other polymer composites.