Hemp (<i>Cannabis sativa</i> L.) fibers (HFs) were utilized for the preparation of HFs-reinforced unsaturated polyester (UPE) composites. To improve the interfacial adhesion between HFs and UPE matrix, some chemical strategies were developed to induce the HFs with unsaturated functionality and hence form covalent bonds with UPE resin via a free-radical polymerization. For example, the surface modification of HFs with 3-isopropenyl-dimethylbenzyl isocyanate (TMI) significantly increased the mechanical properties and water resistance of the resulting HF-UPE composites. On the other hand, currently used UPE resins contain a considerable amount of styrene that is potentially carcinogenic; the use of amount of petroleum-based resources in the synthesis of UPE resins is also unsustainable. Therefore, a series of styrene-free UPE and acrylated epoxidized soybean oil (AESO) were formulated to fabricate environmentally friendly biocomposites. AESO was used as a biobased substitution of UPE. A highly reactive vinyl monomer, i.e., <i>N</i>-vinyl-2-pyrrolidone (NVP), was used as styrene replacement during the production of UPE and AESO biocomposites with HFs. To simultaneously improve the crosslinking density of AESO resins and the interfacial adhesion between HFs and AESO, two bifunctional isocyanates, i.e., isocyanatoethyl methacrylate (IEM) and TMI, were used as reactive diluents to replace styrene for AESO resins, respectively. The incorporated IEM or TMI carrying both C=C bonds and isocyanate groups not only would crosslink with the C=C bonds of AESO, but also react with the hydroxyl groups of both AESO and HFs to concurrently improve the unsaturation level of AESO monomers and the fiber-matrix interfacial adhesion of the composites. Finally, the developed HF-reinforced biocomposites were compared to their analogues such as bamboo fibers-reinforced biocomposites.

Utilization of hemp fibers as reinforcements in biocomposites

2019 Spring National Meeting

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