Environmentally friendly Poly(lactic acid)/Phormium Tenax composite: Thermal and Mechanical characterization

The effect of the introduction of variable contents of Phormium tenax (New Zealand flax) fibres, namely 20, 30 and 40 wt.%, in a poly(lactic acid) matrix has been characterised thermally and mechanically. The polymer and plant fibres were extruded in a micro-compounding system and the specimens were obtained through injection moulding. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed that cold-crystallization peak shifted to lower temperatures with the increasing fibre content, and it is confirmed that the addition of phormium fibre enhanced the degree of crystallinity. The TGA analysis confirmed that the addition of natural fibers in the PLA matrix decreased the thermal stability of the neat PLA. Dynamic mechanical analysis (DMA) results confirmed that the addition of untreated phormium fibre did not affect the Tg of the samples and the area under the tan δ decreased with the addition of phormium fibre, i.e. the damping ability of PLA based composites is less compared to pure PLA. The results show that the tensile modulus has been consistently increased by reinforcing the composite with growing amounts of fibres, whilst the effect on tensile strength is less evident, as is the case in a large number of lignocellulosic fibre composites. Fracture surfaces of the tensile samples have been characterised by scanning electron microscopy (SEM), which allowed highlighting failure modes of the composites.