An Ultra-High Bonding Strength Poly(Propylene Carbonate)-Based Adhesive for Plywood Enhancement

The increasing demands for environmental adaptability and recyclability in high-performance hot melt adhesives have driven the development of a novel material with ultra-high bonding strength. In this work, biodegradable poly(propylene carbonate) (PPC) and high-strength polyethylene terephthalate glycol (PETG) were linked via chain extension using methylene diphenyl diisocyanate to fabricate a PPC-PETG hot melt adhesive. The resulting adhesive exhibits exceptional adhesion across a wide range of substrates, achieving a maximum single-lap shear strength of 29.9 MPa on stainless steel. Notably, after five consecutive recycling cycles, the adhesive strength remains as high as 21.0 MPa. The PPC-PETG adhesive also demonstrates excellent resistance to both acidic and alkaline environments on stainless steel substrates, with single-lap shear strength significantly improved compared to neutral conditions. Its overall performance substantially surpasses that of conventional commercial adhesives and previously reported counterparts. In practical applications, this adhesive has been successfully used to fabricate high-performance plywood by bonding various hardwoods and softwoods, yielding flexural strengths of at least 150 MPa and flexural moduli of at least 14 GPa.