Use of secondary fibres from recycling processes of fibreboard manufacturing and post-consumer waste in medium density fibreboard

Abstract Recycling medium-density fibreboard (MDF) enhances material efficiency and contributes to waste management. This study investigates the impact of secondary fibres, generated from recycling of both processing and post-consumer waste, on the properties of new MDF panels. The fibres were recycled using a modified thermo-mechanical pulping (mTMP) and steam treatment (ST) processes. Virgin pine and secondary fibres were studied for their size distributions and morphological features. MDF panels were fabricated by substituting virgin fibres with secondary fibres at 15% and 25% rates, with additional 100% recycled MDF produced using ST-obtained fibres. Secondary fibres from both waste sources were shorter and had more fines than virgin fibres. For recycled MDF incorporating ST fibres, a notable drop in internal bond strength was observed when using fibres from post-consumer fibreboard waste, while modulus of rupture, modulus of elasticity, thickness swelling, and water absorption remained consistent. Increasing substitution rates from 15 to 25% resulted in an insignificant change in the aforementioned physical and mechanical properties. However, MDF produced with 100% recycled fibres exhibited a dramatic decrease in physical and mechanical properties, despite a reduction in formaldehyde content. Compared to MDF with virgin fibres, the internal bond strength of recycled MDF statistically decreased at all substitution ratios. In contrast, other properties were comparable at 15% or 25% rates for fibres produced using the mTMP process. Finally, MDF containing mTMP fibres showed similar density profile values, slightly higher than MDF with ST fibres.