Crosslinking networks in epoxidized natural rubber/hemp hurd bio‐composites for the enhancement of thermal, mechanical, and water repellence properties

Epoxidized natural rubber (ENR) bio‐composites filled with hemp hurd were fabricated via reactive batch‐mixing and vulcanization. The effect of the ENR‐hemp hurd grafting, silane modification, sulfur vulcanization, and the built‐up crosslinking networks on the thermomechanical and physical properties were analyzed. It was observed that the reactive mixing of ENR and hemp hurd caused epoxy ring opening followed by ether bonding of ENR onto the hemp hurd. There was evidence showing that the hemp fillers were also involved in the sulfur vulcanization. The sulfur vulcanized ENR bio‐composites displayed a low swelling index, homogeneous filler dispersion, and superior thermomechanical properties. The vulcanized bio‐composites with silane‐modified hemp hurd showed slightly less grafting but substantially reduced water absorption. The hardness, tensile strength, and modulus of the optimized formulation displayed a 300%, 1030%, and 960% enhancement as compared to the ENR baseline, respectively.