Macadamia (Macadamia integrifolia) shell and castor (Rícinos communis) oil based sustainable particleboard: A comparison of its properties with conventional wood based particleboard

The present study examines the suitability of particleboard made from ground macadamia nut shells bonded with castor oil derived resin as an environmentally sustainable substitute for conventional wood fiber/urea formaldehyde particleboards. The properties of the macadamia shell castor oil resin particleboard were compared with those of a wood fiber/castor oil resin particleboard and a conventional wood fiber/urea formaldehyde particleboard. The density of the macadamia shell particleboard was 43% higher than that of its wood fiber counterpart, in keeping with the higher density of the macadamia shells. Water absorption and water-induced swelling were much lower in the macadamia shell particleboard, being only one quarter of the value obtained for the wood fiber particleboard. This is consistent with the lower moisture absorption reported previously for macadamia shells. The internal bond strength was similar for the macadamia shell and wood fiber particleboards bonded with castor oil based polyurethane. The modulus of rupture and modulus of elasticity were however about 50% lower for the macadamia shell particleboard than for its wood fiber counterpart. This is considered to be due, at least in part, to the lower cellulose content of macadamia shells. Formaldehyde emissions from the castor oil resin particleboards were less than 5% of those typical of urea formaldehyde particleboards. Based on these findings it is considered that macadamia shell/castor oil particleboards have acceptable properties for use in the built environment. Their good moisture resistance makes them particularly attractive for use in humid environments, such as in bathroom and kitchen applications. Moreover, they have much lower environmental impact than conventional particleboards.