Understanding the Effects of Cross-Linking Density on the Self-Healing Performance of Epoxidized Natural Rubber and Natural Rubber

Abstract

The demand for self-healing elastomers is increasing due to the potential opportunities such materials offer in reducing down-time and cost through extended product lifetimes and reduction of waste. However, further understanding of self-healing mechanisms and processes is required in order to develop a wider range of commercially applicable materials with self-healing properties. Epoxidized natural rubber (ENR) is a derivative of polyisoprene. ENR25 and ENR50 are commercially available materials with 25 and 50 mol % epoxidation, respectively. Recently, reports of the use of ENR in self-healing materials have begun to emerge. However, to date, there has been limited analysis of the self-healing mechanism at the molecular level. The aim of this work is to gain understanding of the relevant self-healing mechanisms through systematic characterization and analysis of the effect of cross-linking on the self-healing performance of ENR and natural rubber (NR). In our study, cross-linking of ENR and NR with dicumyl peroxide and sulfur to provide realistic models of commercial rubber formulations is described, and a cross-linking density of 5 × 10 –5 mol cm –3 in sulfur-cured ENR is demonstrated to achieve a healing efficiency of 143% for the tensile strength. This work provides the foundation for further modification of ENR, with the goal of understanding and controlling ENR’s self-healing ability for future applications.

Thermally Reprocessable Self-Healing Single-Ion Conducting Polymer Electrolytes

“…11 Additionally, the brittleness increased with higher furan composition due to a decrease in the average chain length between cross-linking points. 54,55 When comparing the stress−strain behaviors of xLs with xLPs, we found that PEO units from PEGFMA did not significantly impact the mechanical properties, despite their low T g . We assume that the mechanical properties of xLPs may be reinforced by the ion−dipole interaction between lithium ions and PEO units.…”

Dual X-ray- and Neutron-Shielding Properties of Gd2O3/NR Composites with Autonomous Self-Healing Capabilities

“…After the compounding, the NR samples were vulcanized using hot compression molding (CC-HM-2060, Chaicharoen Karnchang Co., Ltd., Bangkok, Thailand) at 150 °C and a pressure of 160 kg/cm 2 for 150 secs in a mold with dimensions of either 15 cm × 15 cm × 0.2 cm or 10 cm × 10 cm × 0.2 cm. Notably, the procedure for sample preparation was mainly based on the published works of Xu et al [ 23 , 24 ], while the cure time of 150 secs was selected following preliminary studies for optimized cure times, for which shorter or longer cure times resulted in the samples being too soft or too hard, respectively, which limited their useability and prevented the initiation of self-healing mechanisms from occurring [ 26 ].…”

Effects of polyamide elastomer on the morphology, crosslink density, mechanical, and oil‐resistant properties of acrylonitrile‐butadiene rubber/polyamide elastomer vulcanizates

“…Crosslink density is an important parameter that dictates the physical properties of vulcanizates. The type and degree of crosslinking network of the vulcanizates determines the physical properties, such as modulus, hardness, and tensile strength 12–14 . Three main vulcanization systems, namely phenolic resin vulcanization, sulfur vulcanization, and peroxide vulcanization systems, are widely used for the vulcanization of NBR.…”

“…The type and degree of crosslinking network of the vulcanizates determines the physical properties, such as modulus, hardness, and tensile strength. [12][13][14] Three main vulcanization systems, namely phenolic resin vulcanization, sulfur vulcanization, and peroxide vulcanization systems, are widely used for the vulcanization of NBR. Phenolic vulcanization gives rubber good mechanical properties and heat resistance, and it is the predominant vulcanization system used in industry to produce thermoplastic elastomers (TPE).…”