Impact of corona treated hemp fibres onto mechanical properties of polypropylene composites made thereof

The mechanical properties of composites obtained from different combinations of untreated and corona treated fibres and polypropylene were characterized by tensile and compressive stress–strain measurements. Extrusion–compression moulding was used as the method of preparation and the quality of fibre dispersion as well as the validity of our process were verified via tensile test on samples cut in two different directions. The influence of fibre content in composites is reported and it appears that an amount of 20% leads to the maximal values of tensile strength and Young moduli, whether the fibre is treated or not. Besides, the results show that the treatment of compounds (fibres or matrix) leads to a significant increase in tensile strength. The modification of cellulosic reinforcements rather than polypropylene allows the greater improvement of the composites properties with an enhancement of 30% of Young modulus. The etching effect generated by CDT and evidenced by microscopy is mostly responsible for the enhanced mechanical anchorage and interfacial adhesion between the compounds. It is noteworthy that the same trends were obtained for compressive test. The observation of the fracture surfaces allows discussion about adhesion improvement.