Upcycling wood waste into fibre-reinforced magnesium phosphate cement particleboards

Upcycling contaminated wood waste by magnesia-phosphate cement (MPC) into rapid-shaping cement-bonded particleboards is a promising technology. MPC binder exhibited superior compatibility with wood waste. However, there is a need to address the limitations of high brittleness, low strain capacity, and low water resistance of MPC products. High content of recycled wood in the MPC particleboards (20 wt%) should be accomplished without compromising their mechanical strength and durability. In this study, the addition of 2% (v/v) polyvinyl alcohol (PVA) fibre significantly reinforced flexural strength and fracture energy of particleboards, as high as 56.5% and 891.9%, respectively. The characteristics of PVA fibre determined the efficiency of reinforcement. At the same dosage, addition of shorter fibre (3 mm in length) presented higher strength, whereas incorporation of longer fibre (12 mm) improved fracture energy. Thinner fibre (35 µm in diameter) showed a larger increase in both flexural strength and fracture energy. Surface morphology of PVA fibre played an important role in determining the reinforcement mechanisms and reinforcing efficiency. Under stress, hydrophobic fibres (oil-treated) were pulled out from MPC matrix, whereas hydrophilic fibres (untreated) were ruptured. The former showed higher reinforcing efficiency for MPC particleboards. The fibre-reinforced particleboards maintained sufficient mechanical strength and dimensional stability after 24-h water immersion or 1-h heating at 100 °C, which fulfilled the standard requirements. This study demonstrated that PVA fibre addition is an effective method to reinforce mechanical properties as well as thermal and water resistance of MPC particleboards.