Developing polylactic acid (PLA)-based medium-density fiberboard: investigating three key manufacturing factors and their impact on physical and mechanical properties

The effect of particle size, weight% of polylactic-acid (PLA) powder, and clamping pressure on the physical and mechanical properties of medium-density fiberboard (MDF) manufactured from thermomechanical pulp were studied using the Taguchi experimental design method. According to the L9 type Taguchi experimental design array, the impact of the three factors was examined at three levels, with the target density of the MDF set at 750 kg/m³. The 4 mm thick MDF panels were prepared by applying pressure in the range of 4, 6, and 8 N/mm², using powdered PLA with particle sizes of ⌀<0.1, 0.1<⌀<0.25, or 0.315<⌀<0.4 mm, at weight percentages of 10, 20, and 30. The results indicated that the optimal setup for achieving the highest modulus of rupture (MOR), modulus of elasticity (MOE), and the lowest thickness swelling (TS) was using 30% PLA (by weight%) with particle sizes between 0.1 and 0.25 mm, and applying a clamping pressure of 6 N/mm². Applying the optimal factor setups and increasing the density to 840 kg/m³ resulted in an average MOR of 21.4 N/mm², MOE of 8003 N/mm², IB of 0.46 N/mm², and a TS of 49.4% after 24 hours. The validation board’s dynamic mechanical analysis (DMA) graphs showed that the glass transition temperature (T_g) of the PLA + fiber composite increased compared to the cold crystallized pure PLA, and a steep drop in storage modulus (E’) couldn’t be observed in the initial rubbery region. The absence of a steep drop in storage modulus (E’) in the initial rubbery region suggests that adding fibers enhances the material’s ability to withstand higher temperatures before transitioning to a rubbery state.