Economical particleboard production using hardwood sawmill residues

Particleboard often represents the lowest cost option amongst a range of suitable wood panel products. Particleboard consumption in the world is approximately 57% of total wood panel consumption and the demand is growing at 2 – 3% per year. This demand required more and more wood chipping to supply the raw materials as particleboards are traditionally made using custom flaked softwood particles. Hardwood sawmill residues have traditionally not been favoured by the particleboard industry (or indeed other forest product industries) owing to their high density and high extractive content. Throughout Australia considerable quantities of hardwood saw mill residues are produced as solid waste. In Victoria alone, over a million cubic metres of saw logs are converted annually into sawn timber, producing in excess of 200,000 tonnes of hardwood sawdust. In recent years, the re-growth and plantation timber industry in Australia has been producing hardwood sawmill residues with lower extractive contents and lower densities. The work presented here is aimed at developing an economical methodology for making particleboard using 100% hardwood sawmills waste. A comprehensive literature review indicated that a similar attempt has not been conducted to date. Through the literature review, major parameters which would influence particleboard made of sawmill waste were established. Subsequently, in consultation with the softwood particleboard industry, a preliminary process of making particleboards in the laboratory was developed. This method was trialled and modified until an acceptable particleboard could be produced. A systematic experimental investigation was then performed incorporating a design of experiments method (DOE) and analysis of variance (ANOVA) to investigate the behaviour of single-layer and three-layer particleboard properties separately with processing parameters. Seven processing parameters were studied for three-layer boards while six parameters were studied for single-layer boards. The particleboard testing was performed according to the Australian and New Zealand standards for reconstituted wood-based panels. It was found that three-layer particleboards can be produced using 100% hardwood sawmill residues as the major raw material to meet the standards for general purpose particleboard. This hardwood particleboard uses a slightly higher amount of resin and moisture for its surface layer than conventional softwood particleboards. To understand the effect of processing parameters on the particleboard properties, further analysis was conducted. Based on this analysis, process models were developed to predict the most critical particleboard properties (modulus of elasticity, modulus of rupture and the vertical density profile) with respect to processing parameters. These models can be used to optimise properties of hardwood particleboard with regard to processing parameters. Also, these models can be used to produce particleboards in the laboratory with required design properties