A green magnesium oxychloride cement based adhesive synergistically reinforced by citric acid and polyvinyl alcohol fibers for wood

Magnesium oxychloride cement (MOC) has the advantages of no formaldehyde emission, fire resistant and curing at ambient temperature, which make it to be a promising wood adhesive for wood industry. However, the poor permeability of MOC on wood surface and the inherent brittleness of MOC limit its practical application. To solve these problems, citric acid (CA) and polyvinyl alcohol (PVA) fibers were demonstrated to synergistically promote the bulk penetration of MOC in wood surface and enhance the toughness of MOC, which resulted from the pH regulating effect of CA and the toughening effect of PVA fibers and CA. Based on this synergistic method, the compressive strength and toughness of the obtained MOC/CA/PVA adhesive were higher than that of pure MOC adhesive. Moreover, the wet adhesive strength of the MOC/CA/PVA adhesive reached 1.81 MPa, which increased by 33% than pure MOC adhesive. In addition, the wood products bonded by the modified adhesives possessed excellent flexural performance and fire resistance. This modification strategy makes the modified MOC-based wood adhesive have great application potential in wood and building industry.