Influence of processing conditions and material compositions on the performance of formaldehyde-free wood-based composites

This study examined the differences between formaldehyde-free wood composite panels made with maleated polyethylene (MAPE) and maleated polypropylene (MAPP) binding agents. Specifically, the study investigated the contrasts of (a) base resin type, PE vs. PP, (b) molecular weight/maleic anhydride content in MAPP binding agents, and (c) the manufacturing methods (reactive extrusion vs. hot press) on the physicomechanical properties of the composites. FTIR and XPS analyses of unmodified and modified wood particles after reactive extrusion with maleated polyolefins provided evidence of chemical bonding between the hydroxyl groups of wood particles and maleated polyolefins. Although extruding the particles before panel pressing gave better internal bond (IB) strength, superior bending properties were obtained through compression molding alone. MAPP-based panels outperformed MAPE-based panels in stiffness. Conversely, MAPE increased the 113 strength of the panels compared with MAPP. Polymer base resin had no effect on modulus of rupture or screw holding capacity. Differences between the two maleated polypropylene compounds were not significant for any of the mechanical properties tested. Formaldehyde-free wood composites manufactured in this study often outperformed standard requirements for conventional particle-board, regardless of material composition or manufacturing method used.