Self-Healing Natural Rubber (NR) Based on Zinc Diacrylate (ZDA) Networks

Abstract

Rubber product waste has an impact on the environment that goes beyond landfills. Due to the long degradation phase of rubber materials, improper disposal can lead to the release of potentially hazardous substances and environmental pollution. Self-healing offers an alternative to investing in environmentally manufactured products to reduce these harmful environmental effects. Zinc diacrylate was grafted into natural rubber as a self-healing substance. This study aimed to examine the effect of zinc diacrylate, as a self-healing agent, on the properties of zinc diacrylate grafted natural rubber. The tensile properties of the cured rubber were tested before and after the healing process to determine the healing efficiency of the zinc diacrylate grafted natural rubber, and it achieved 72% healing efficiency. The crosslink density test findings indicate that the covalent crosslink density increased with increasing zinc diacrylate content. In contrast, the ionic crosslinking increased with increasing zinc diacrylate content until it reached a maximum value at NR/10ZDA and decreased at 20 phr of zinc diacrylate. Covalent and reversible ionic interactions were present in NR/10ZDA and NR/20ZDA. FESEM images corroborated the results, showing that NR with 10 phr of zinc diacrylate had the best tensile strength, elongation at break, and self-healing ability. The fractured contact surface of NR/10 ZDA revealed no discernible gap, indicative of a highly effective self-repairing process. This study demonstrates zinc diacrylate’s potential as a self-healing agent that could render a new era of ecologically friendly rubber goods.