Adhesion and Cohesion Performance of Polyurethane Made of Bio‐Polyol Derived from Modified Waste Cooking Oil for Exterior Grade Plywood

This study explored the feasibility of Waste Cooking Oil (WCO)-based Bio-Polyurethane (Bio-PU) as an eco-friendly alternative to petroleum-derived polyols in plywood adhesives. The objective is to evaluate the impact of varied WCO concentrations and methylene diphenyl diisocyanate (MDI) levels on Bio-PU and plywood performance. The Bio-PU's characteristics, rheology, and functional groups are studied. Plywood made from three layers of 100 mm x 100 mm × 2 mm rubberwood (Hevea brasiliensis) veneer is bonded with Bio-PU using a dual spread approach at 180 g.m−2, hot pressed at 120 °C and 1 MPa for 4 min. The laboratory-fabricated plywood is tested for physical, mechanical, and adhesive properties. Results showed that Bio-PU exhibited unique adhesive characteristics, with excellent adhesive strength, despite a slight decrease with higher WCO concentrations. WCO insertion do not compromise delamination resistance. FTIR analysis confirmed successful polyurethane chain synthesis. This research highlighted the potential of WCO-based Bio-PU's as a sustainable, high-performance plywood adhesive.