Characterization of millet (Pennisetum glaucum) husk fiber (MHF) and its use as filler for high density polyethylene (HDPE) composites

Abstract

Mechanical properties were investigated for millet husk (MH) fiber filled high density polyethylene (HDPE) composites. The chemical and thermal attributes of the fibers are also studied. The fibers were pulverized to 250 µm size. The composites were prepared by a melt blending technique using a Brabender® internal mixer, accompanied by hot compression. Composite formulations were based on; 10%, 20%, 30%, and 40% wt fiber loadings with 170 oC temperature, 10 min flow time, and 20 rpm rotational speed. Mechanical properties were obtained according to ASTM D3039, ASTM D790, and ASTM D256 for tensile, flexural, and impact test, respectively. Microstructures of fracture tensile test specimens were observed by SEM. Fiber chemical compositions were determined using acid detergent, neutral detergent, and acid detergent lignin to evaluate the cellulose, hemicelluloses, and lignin contents correspondingly. The percentages were 50.4% cellulose, 23.7% hemicelluloses, and 13.2% lignin with remains of other chemical constituents. Thermogravimetric analysis showed that the highest stable temperature was 245 oC. The tensile and flexural strength of the composites decreased with increasing fiber loading, while their modulus increased with increasing fiber loading. The impact strength was reduced drastically as fiber loading was increased. Therefore, it was concluded that millet husk fiber has potential to be used as raw material in composites applications.