Assessment of dicumyl peroxide ability to improve adhesion between polylactide and flax or hemp fibres

Dicumyl peroxide (DCP) is commonly applied as a cross-linking agent in polymer processing. The main aim of this work was to assess the ability of DCP to improve adhesion between polylactide (PLA) and flax or hemp fibres by their interphase cross-linking. Short fibre-reinforced PLA composites were manufactured due to the importance of short fibres in injection moulding of high-quality biocomposites. Reactive extrusion of the PLA, flax or hemp fibres, and DCP was performed. The flax or hemp fibre content was 10 wt%, while DCP varied with 0.5 and 2.5 wt%. The fibres and PLA were mechanically mixed, extruded, granulated and injection moulded to form samples for testing. The samples were characterized by differential scanning calorimetry (DSC), tensile and impact strength tests, dynamic mechanical analysis and scanning electron microscopy (SEM). It was found that flax and hemp fibres increased the Young's modulus while these fibres decreased the impact strength. Addition of DCP led to increase in PLA crystallinity at the interface with fibres which led to further decrease in impact strength. For that reason, it was concluded that DCP is an ineffective agent to improve interphase adhesion between PLA and short flax or hemp fibres.