Mechanical recycling of polylactic acid composites reinforced with wood fibres by multiple extrusion and hydrothermal ageing

Abstract

The mechanical recycling of polylactic acid composites reinforced with wood fibres was studied by multiple extrusions. The composite material was extruded seven times, and the mechanical and thermal properties were monitored by tensile tests, flexural tests, differential scanning calorimetry, Fourier-transform infrared and scanning electron microscopy. The results showed that the material retained its mechanical properties relatively well, for up to five cycles after which the tensile strength decreased by 23%. Thermal characterisation further showed that the glass transition temperature ( Tg) shifted several degrees centigrade towards lower temperatures, further indicating degradation of the polylactic acid polymer. Characterisation was also done on composite material, which was aged hydrothermally between each extrusion cycle in order to simulate post-consumer recycling of composite products, which had been exposed to water. Samples were aged at 50℃ in distilled water for 5 days. The thermal and mechanical testing showed that the material survived the ageing test fairly well.