Enhancing self-healing efficiency of natural rubber composites using halloysite nanotubes

Abstract

This study aimed to explore the reinforcement effect of halloysite nanotubes (HNTs) in self-healing natural rubber based on metal thiolate ion networks. The amount of HNTs was varied at five levels (2, 4, 6, 8, and 10 phr) in order to assess the optimum amount of filler for self-healing efficiency and mechanical recovery performance. Fourier-transform infrared (FTIR) provides evidence for the reversible ionic bonding, facilitated by Zn2+ and S− bonding from the metal thiolate vulcanization with rubber molecular chains. Scanning electron microscopy (SEM) revealed that the NR/HNTs composites with lower filler loading exhibited better recovery, as there were no observable gaps between the cut surfaces of the samples. The results also revealed that addition of HNTs resulted in a significant improvement in the mechanical performance, particularly the tensile strength, which increased by approximately 20%–75%. Furthermore, the extent of healing after the broken pieces were brought in contact with each other varied from 87% to 98%, depending on HNT concentration. Highlights: Fabrication of self-healing elastomers based on natural rubber. Self-healing NR presented enhanced mechanical performance with addition of HNTs. HNTs lumen endows the composites with excellent self-healing efficiency. Developed NR/HNTs composite exhibited room temperature self-healing properties. Reversible ionic bonding expedited by Zn2+ contributes in excellent self-healing.