Effect of kenaf fibre modification on morphology and mechanical properties of thermoplastic polyurethane materials

The presented study examined the morphology and mechanical properties of biocomposites obtained from kenaf natural fibre and thermoplastic polyurethane. Kenaf was modified using various methods, namely: acetylation, blocked isocyanate, maleic anhydride and permanganate treatment. Those methods and ways of carrying out of surface modifications were not studied before on kenaf/thermoplastic polyurethane composites. Different fibre loadings: 10% and 30% (by weight) were applied. The chemical treatments of fibres was confirmed by FTIR. The fibres surface and adhesion of the fibres to matrix was investigated using a scanning electron microscope (SEM). The modulus, tensile strength, elongation at break, hardness, resilience and water absorption were also determined; all results were compared with a untreated kenaf fibre composite. SEM investigations of fibres showed the differences of fibre surface after the chemical treatment. A good adhesion between the polymer matrix and fibres was observed for PU/PMn-KF 30 sample. DMA results indicated that the greatest values exhibited samples with fibre treated by acetylation and permanganate treatment. Increasing the amount of fillers in the polymer matrix leads to higher hardness values and water uptake. Tensile strength and resilience of composites decreased when a higher proportion of kenaf fibre was added. It was observed that the treated fibre composites showed improvement in tensile properties, hardness, resilience and lower water uptake for composites with 10% fibre loading.