Reinforcement of polypropylene with natural fibers : mitigation of environmental pollution

Abstract

Recently, natural fibers have gained research attention in reinforcing polymers due to their availability and unique properties in polymer applications. Preliminary studies indicate indiscriminate disposal of human hair (HH) and the burning of cow hair (CH) and sheep hair (SH) by abattoir operators in Nigeria; this has become a source of concern owing to the hazardous nature of these activities to human health and the environment. This study is, therefore, essential and seeks to utilize these waste materials in an environmentally sustainable way, as the hair fibers used in this work are renewable and will enhance the economy of any country if adequately utilized. The composites of Polypropylene (PP), human, sheep, and cow tail hair fibers were prepared at different weight percentage concentrations of 0, 2, 4, 6, and 8 w% using an injection molding machine. Untreated and treated PP composites were analyzed for average diameter, length, and density; the composites were also characterized for ultimate tensile strength, flexural strength, hardness, and impact strength. The average diameter assessment indicates viz: Cow tail hair > Human hair > Sheep hair. The sequence for hair fiber lengths shows that Sheep hair > Human hair > Cow hair, and the order for average density is Cow tail hair > Human hair > Sheep hair. The analysis of the mechanical properties of the reinforced and unreinforced PP composite showed that the Human hair/PP composite gave the best enhancement for ultimate tensile strength and modulus, flexural strength, and modulus at 8% fiber loading. Cow tail hair/PP composite yielded the best elongation at break at 2% fiber loading. Human hair/PP composite showed the best yield for impact strength at 4% fiber loading, while the Cow tail hair composite performed best for the hardness test at 2% fiber loading. The surface scanning electronic microscope (SEM) images showed no significant manufacturing defect on composites except for the air entrapment in the image of cow tail hair. The study also observed that there is no fiber breakage or void observed in the images. SEM images of the PP-composites interface at 8% maximum loading showed reasonably good fiber adhesion to the polymer matrix. This study is recommended for environmental sustainability and to improve material properties for various applications.