The effect of fibre surface treatment and coupling agents to improve the performance of natural fibres in PLA composites

This paper describes work carried out to assess the effect of fibre treatments and coupling agent on the mechanical performance of PLA composites reinforced with 20 wt% fibre. The chemically-treated harakeke and hemp fibres used to produce fibre mats. Maleic anhydride (MA) grafted PLA (MA-g-PLA) was used as a coupling agent. Composites with fibre treated with silane and dicumyl peroxide (DCP) and composites using MA-g-PLA were characterised by swelling testing, scanning electron microscopy (SEM), tensile testing, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). It was found that the interfacial bonding for composites with fibres treated using silane and peroxide and composites coupled with MA-g-PLA noticeably improved supported by lower swelling indices, higher tensile strengths and lower tan delta compared to those composites with fibres treated using alkali only, with the highest tensile strength of about 11% higher obtained from composites treated with MA-g-PLA followed by silane and then peroxide. However, using silane, peroxide and MA-gPLA as additional composite treatments increased significantly the composite failure strain by up 11, 19 and 30%, respectively for harakeke composites and by 13, 24 and 30%, respectively for hemp composites.