Thermal and mechanical characterisation of Phormium tenax-reinforced polypropylene composites

Composites including short and randomly arranged Phormium tenax fibres in a polypropylene (PP) matrix (fibre content of 20, 30 and 40wt%) were produced by twin-screw compounding and injection moulding. They have been characterised by tensile testing, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results indicated that tensile modulus has been increased by reinforcing the matrix with growing amounts of fibres, whilst the effect on tensile strength had lower evidence. Fracture surface characterisation by SEM indicated that debonding and pull-out are prevalent, which suggests the need to optimise the interfacial bonding. Thermal characterisation results have shown that the main degradation peak for PP was slightly shifted to higher temperatures with the increasing fibre contents, thus improving the thermal stability of the composites. The introduction of fibres did not result in a significant variation in the position of the peaks for calorimetric analysis, except for the melting peak, which appeared lower for the composites with respect to the neat matrix. A slight increase in crystallinity was also measured.