Thermal and mechanical behaviour of recycled short milled carbon fibre reinforced polypropylene and recycled polypropylene composites: A comparative study

Environmental and economic factors have driven research into the recycling and applications of recycled carbon fibres (rCF). This paper presents a comparative study characterizing and comparing the mechanical and thermal performance of recycled short milled carbon fibre (rSMCF) on virgin and recycled polypropylene composites. The effects of rSMCF on VPP and RPP on mechanical performance were analysed and compared. At 5 wt% rSMCF, recycled polypropylene achieved 52.3% and 47.3% improvement on tensile and flexural modulus, while at the same rSMCF loading, virgin polypropylene only improved 37.7% and 17.5%, respectively. The un-notched impact strength of RPP-based composites reduced from 83.2 kJ/m² to 60.1 kJ/m² when rSMCF content increased from 1 wt% to 5 wt%, indicating future work should enhance the fibre/polymer interface performance. Crystal contents (χ₀) of the PP/rSMCF composites were investigated by differential scanning calorimetry (DSC), and the results were analysed and mapped to the mechanical performance. The results of this study propose a novel scalable method for the production of high-performance VPP/RPP composite materials using rSMCF.