Self‐healable and recyclable nitrile rubber based on thermoreversible ionic crosslink network

Abstract

In this work, commercial carboxylated nitrile butadiene rubber (XNBR) was ionically crosslinked with zinc thiolate forming reversible ionic salt bonding between carboxy groups (COOH) in XNBR chains and Zn2+ ions from zinc thiolate. The reversible nature of the ionic crosslinks allows rearrangement of rubber molecular chains under an external heat and provides self‐healing capability to the materials. The amount of zinc thiolate was varied at five levels (10, 20, 30, 40, and 50 per hundred rubber (phr) to assess the maximum reaction between COOH and Zn2+ ion for the formation of ionic crosslink networks. Evidence that ionic crosslinks formed within the materials was determined by the increased of curing torque and the chemical interaction was identified by Fourier transform infrared spectroscopy. An equilibrium swelling testing quantitatively measured the ionic crosslink density within the material and XNBR with 30‐phr zinc thiolate showed the highest ionic crosslink density. The results revealed that, damaged XNBR with 30 phr zinc thiolate able to recover 98% of its initial properties under thermal healing at 150°C for 10 min. Furthermore, the material can be reprocessed and recycled for three times without compromising its initial properties. Perhaps, the tensile strength increased 360% at approximately 23 MPa, after third recycling process. In addition, the self‐healing XNBR also have excellent weldability on the damage sample, which shows high potential for repairing of existing rubber products installed in heavy engineering applications.

Unlocking the potential of self-healing and recyclable ionic elastomers for soft robotics applications

“…But beyond the numerical results, the simplicity of the process introduced, the use of low-cost ingredients and the optimization of repair conditions place this development in an advantageous position. Zainol et al 69 developed XNBR compounds using the same zinc-carboxylate metal-ligand interaction, but with zinc thiolate (ZT) and dicumyl peroxide (DCP) in their recipes. Employing a considerably higher amount of ZT (30 phr), a TS of up to 8 MPa was achieved, coupled with a healing efficiency of 98%, at a higher temperature (150 1C), but with a reduced repair time (just 10 min).…”

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

“…This could be attributed to the excellent rubber and HNT lumen interaction. The material's healing ability is primarily determined by ionic interactions between polymerized and homo‐polymerized zinc thiolate, a decrease in unoccupied space in natural rubber matrix with increased HNTs loading results in reduced healing recovery 48 …”

“…The material's healing ability is primarily determined by ionic interactions between polymerized and homo-polymerized zinc thiolate, a decrease in unoccupied space in natural rubber matrix with increased HNTs loading results in reduced healing recovery. 48 The elongation at break values of NR/HNT0, NR/HNT2, NR/HNT4, NR/HNT6, NR/HNT8, and NR/HNT10 were found to be 1190%, 1169%, 1092%, 1034%, 1012%, and 978% before healing, while 1066%, 1040%, 954%, 886%, 855%, and 794% after the healing process, respectively. It was observed that the incorporation of HNTs reduced the elongation at break of the self-healing rubber compounds.…”

Reprocessable and Recyclable Self-Healing Natural Rubber/Carbon Black Composite Based on Metal Thiolate Ionic Network

“…Welding Test. A welding test based on a procedure conducted previously [24], [27] was carried out to determine the ability of the rubber to weld on the isolated break interfaces. Firstly, a dumbbell sample was cut into two pieces.…”