Reactive maleic anhydride polyolefins (MAPOs) in oriented strand board. Part 1: Dynamic thermomechanical properties of phenol formaldehyde resins blended with two MAPOs

Abstract

Abstract A mechanism to improve the toughness of phenol formaldehyde (PF) resin for wood composites is investigated. It is hypothesized that addition of maleic anhydride polyolefins (MAPO), namely maleic anhydride polypropylene (MAPP) and maleic anhydride polyethylene (MAPE), to PF resin will toughen it owing to phase separation between the resin and MAPO. Dynamic mechanical analysis of resin with a low level of MAPP (0.5%) showed an improvement in the storage modulus (E′) or stiffness of the resin system during curing. Similarly, the damping property, tanδ, examined at three discrete temperatures, improved with blends of low levels of MAPP (0.5%). The fracture energies (GIc and GIa) at 12% moisture content were increased with the addition of MAPP at lower proportions (1.5%, 3%, and 4.5%); whereas the addition of MAPE showed a reduction in fracture energies, although not significant, particularly at lower levels. After 24 h soaking, specimens with MAPP showed significant improvements in GIc only at the 3% level; however, addition of MAPE resulted in a reduction of both the fracture energies. On the basis of these results, PF resin was blended with MAPP anionic emulsion for fabrication of oriented strand composites (OSC) test boards in Part 2 of the study.