Self-healable and recyclable carboxylated nitrile butadiene rubber (XNBR)
Loading...
Date
2019-07
Authors
Tan Mei Ping
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
In order to meet the requirement of final product, gum rubber need to be crosslinked to form 3D covalent network. However, the vulcanization process turns the material to act like thermoset with the impossibility to self heal and recycle. From the view point of sustainable development of rubbers, it is substantial to integrate the selfhealing and reprocessing capability into commercial rubber. The objective of this study was to develop healable and recyclable carboxylated nitrile butadiene rubber (XNBR) that consists of reversible crosslinks network which can be ruptured and reconstructed back when they are damaged. In this work, ionic crosslinks network was introduced into XNBR through peroxide vulcanization system with addition of different zinc thiolate amount (0, 10, 20, 30, 40, 50 phr) in order to assess optimum amount of zinc thiolate for healability and recyclability performance. Healing efficiency was measured through universal tensile tester over a range of healing time and healing temperature. It was found that XNBR with 30 phr zinc thiolate exhibited the highest healing capability. The results also revealed that the developed self-healing XNBR able to recover 80.88 % of its initial tensile properties in just 5 minutes and 97.87 % in 10 minutes at 1500C. The fracture area was recovered after the healing process as observed using scanning electron microscope (SEM). The optimum compound formulation for XNBR with 30 phr zinc thiolate was chosen to investigate reprocessing and recycling ability of the XNBR. The damaged XNBR was masticated again using heated two-roll mills at 80 0C for 5 minutes and pressed at 150 0C to fabricate new samples. The recycling process was repeated for three times and the tensile performance of the recycled sample was measured each time. The results showed that tensile strength increased even after three time recycled which was believed to occur due to the formation of additional Zn2+ salt bonding, which can selfaggregate forming ion clusters that act as effective reinforcing agent. The mechanism was further evidence by welding test of the broken sample using recycle XNBR. As expected, the tensile strength and tear strength was found higher compared to the neat sample.