AbstractThree different types of recycled polyurethane (PUR) material, two in powder form from a pulverizing process (one < 50 µm and one < 250 µm) and one in polyol form from a glycolysis process, were used as substitutes for polymeric methylene diphenyl diisocyanate (pMDI) resin at 5%, 15%, and 30% ratio, respectively, to replace the pMDI resin for particleboard manufacturing at 8% resin loading. The reactions between pMDI resin and recycled PUR powder and polyol were investigated with Fourier transform infrared (FT-IR) spectroscopy. It was found that 5% substitution of pMDI with recycled PU powder of < 50 µm resulted in significantly higher panel internal bonding (IB) strength than pure pMDI resin, which also tended to increase panel modulus of rupture (MOR), and modulus of elasticity (MOE). Polyol did not show advantages over PUR powder in particleboard application. Increasing the size of recycled PUR powder from < 50 µm to < 250 µm decreased the panel IB, which also tended to decrease MOR and MOE. Recycling PUR materials in either powder or polyol form in particleboard manufacturing did not improve panel thickness swelling, but did appear to improve panel water absorption.