Tensile properties and micromechanical analysis of stone groundwood from softwood reinforced bio-based polyamide11 composites

Bio-polyamides (BioPA) reinforced with natural fibres are one of the most promising bio-based composites. However the principal challenge of polyamides (PA) is their high melting temperature close to the degradation temperature of the natural fibres. Polyamide 11 (PA11) is a 100% BioPA with a melting point lower than cellulose temperature degradation. Nonetheless, few researches about PA11 reinforced with natural fibres composites had been performed. In this work, PA11 was reinforced with stone groundwood fibres (SGW) ranging 20% up to 60% of fibre contents. The composites were prepared, extruded, injected moulded and their tensile properties were characterised. An enhancement of 66.8% was obtained for the tensile strength of the composites, besides the strain and the toughness decreased as expected. The significant enhancement of the tensile strength leads to consider a relatively good interface between the fibre and the polymer matrix which was determined in the micromechanical studies. Moreover a morphology analysis of the fibre and its chemical composition study at surface were carried on, in order to discuss the micromechanical analysis results. The average orientation factor and intrinsic tensile strength of the fibres were also determined in the micromechanical analysis.