The effect of filler chemical constitution and morphological properties on the mechanical properties of natural fiber composites

The purpose of this work was to obtain environmentally friendly natural fibre composites (NFC) from high-density polyethylene (PE-HD) foil and either finely ground sunflower husk or pistachio shells, which both possess physico-mechanical characteristics similar to wood-polymer composite. The composites were prepared from waste materials without the use of additives. It was found that 66% of the sunflower husk grains were from 180 to 850 mu m in size, and 88% of the pistachio shell particles were less than 63 mu m in size. With the use of a rolling mixer, six mixtures were produced with filler shares amounting to 5, 15 and 30wt.% of sunflower husk and 15, 35 and 55% of pistachio shell, from which dumbbell-shaped samples were formed via injection processing. The produced materials were analysed for their mechanical properties (impact strength, hardness, tensile strength, Young's modulus and DMA). The morphologies and chemical composition of the filler as well as the morphological properties of the composites (SEM) were also investigated. The chemical constitution and shape of the filler particles affected the investigated properties of the obtained NFC, and the results were especially significant for the properties of impact strength, stiffness and tensile strength.