Epoxy‐POSS toughened phenol‐formaldehyde resin adhesive and its enhancement on the interfacial bonding strength of bamboo based composite

Abstract Bamboo‐based composite, being an eco‐friendly green material, has garnered widespread utilization across diverse sectors including construction and domestic appliances owing to its impressive strength, innate aesthetic appeal, and wear resistance. However, it tends to crack at bonding interface between bamboo and the brittle resin adhesive due to stress concentration, reducing its mechanical properties and lifespan. To address this issue, the epoxy‐based polyhedral oligomeric silsesquioxane (POSS) was incorporated to modify the phenol‐formaldehyde (PF) resin and improve the interfacial bonding strength. And the results showed that the incorporation of 5% epoxy‐POSS could markedly increase the impact and flexural strength of the modified PF resin by 75.7% and 27.6%, respectively, in contrast to the original PF resin. Moreover, the dry and wet shear strength of bamboo‐PF composites bonded by the POSS modified PF resin adhesive was also apparently improved by 17.03% and 28.55%, respectively. The increased toughness and bonding strength were mainly attributed to the nano‐effect of POSS and good compatibility and cross‐linking reaction with the PF resin, which helped dissipate energy and avoid stress concentration within the PF resin and at the bonding interface. This study aims to address the cracking problem of bamboo‐based composites and extend their longevity in architectural and domestic applications. Highlights Epoxy‐POSS disperse well in PF resin due to its unique multi‐epoxy structure. Epoxy‐POSS can react with PF resin and effectively improve its toughness. Nano‐effect and cross‐linking effect enable dissipate energy and disperses stress. Modification increased bonding strength and decreased interfacial cracking.