Effect of Sodium Hydroxide Treatments on the Tensile Strength and the Interphase Quality of Hemp Core Fiber-Reinforced Polypropylene Composites

摘要

The formulation of greener composite materials by substituting glass fibers with naturalfibers is a current field of research. If such natural fiber reinforcements come from industrial sidestreams, as hemp core fibers (HCFs) come from the extraction of hemp strands for the textile industry,an additional advantage can be identified. Nonetheless, such by-product fibers show some drawbacks,such as high lignin contents, which can make it difficult to obtain a good interphase between thefibers and the matrix and to obtain a good fiber individualization. A digestion treatment at differentNaOH contents is proposed to eliminate soluble lignin and extractives from the surface of the fibers.At the same time, the use of a coupling agent solves incompatibilities between the fibers and thematrix. The composites were tensile tested and the impact of the proposed treatments is evaluatedand discussed. Later, the Kelly-Tyson modified equation and a modified rule of mixtures—themicro-mechanic models—is used to study the impact of such treatments on the quality of theinterphase between the polymer and the reinforcement. Both treatments showed a high impact onthe tensile strength and the quality of the interphase, obtaining competitive composite materialsreinforced with HCFs derived from a by-product