Development of HEMP fiber reinforced polypropylene composites

Nonwoven mats from hemp and polypropylene fibers in various proportions are produced and hot pressed to make composite material. The effect of hemp fiber content and anisotropy in the nonwoven mats resulting from the carding technology are examined on the basis of the three-point bending, tensile, and impact properties of the resultant composite materials. Because of the hydrophilic nature and poor dimensional stability of cellulosic fibers due to swelling, the effect of water sorption on mechanical performances is also investigated. Optimal mechanical properties are achieved in composites made from 40 to 50% of hemp fiber by weight. As expected, better mechanical properties are found in the specimens cut from the composite sheets parallel to the direction of carding. A strong decrease in three-point bending properties is noticed after immersing the composite samples in distilled water for 19 days, while the impact strength increased. Double carding of raw materials results in a decreased anisotropy in the composite material.