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

Abstract

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.Highlights ENR bio‐composites with hemp hurd were fabricated. Crosslinking networks were built‐up within the ENR/hemp bio‐composites. SiHemp show similar reinforcement but more water repellence. The synthesized composites had enhanced thermal and mechanical properties.

Recyclable and Self-Healing Natural Rubber Vitrimers from Anhydride-Epoxy Exchangeable Covalent Bonds

“…Characterization using XPS can be conducted to confirm the changes in chemical composition for evaluating the cross-linking network of rubbers . The surface chemical composition of NR, NR-MA, and NR-MA-DGEBA obtained from XPS was analyzed and is presented in Figure .…”

“…Characterization using XPS can be conducted to confirm the changes in chemical composition for evaluating the cross-linking network of rubbers. 54 The surface chemical composition of NR, NR-MA, and NR-MA-DGEBA obtained from XPS was analyzed and is presented in Figure 3. It is noted that the elemental oxygen was found in the baseline NR sample, which was attributed to residual protein and traces of moisture remaining in the structure of NR when dried from the rubber latex.…”

Sulfur Free Crosslinking of EPDM Composites via Silane Grafting and Silica Incorporation

“…[14][15][16] It has been recognized that building covalent bonds between the matrix and filler would significantly improve the mechanical and thermal properties of the developed composites. [17,18] However, it is worth noting that the majority of investigations on EPDM composites have predominantly employed silane as a coupling agent, with crosslinking networks between the rubber matrix and fillers being absent. [19][20][21][22] Silica, with its cost-efficiency and inherent reinforcing capabilities, has long been revered for its ability to enhance the physicomechanical attributes of various polymers.…”