Thermal stability and self-healing capacity of modified carboxylated nitrile rubber

Abstract

Self-healing materials are becoming a widely discussed topic in materials engineering. Some of them could find applications as electrical insulators. However, the implementation of self-healing capability does not come without compromises in both the structure and properties of the materials. Therefore, these materials must be carefully evaluated before fully integrating into a broad portfolio of electrical insulation materials. An important and still unanswered question is how self-healing materials resist accelerated thermal ageing. This paper summarizes the results of dielectric, thermal, and mechanical properties measurements, before and after accelerated thermal ageing of carboxylated nitrile rubber (XNBR) containing ionic clusters as healing moieties. Simultaneous thermal analysis (STA), differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS), and Fourier transform infrared spectroscopy (FT-IR) were performed. The healing efficiency of the thermally aged samples was evaluated based on tensile strength measurements (before and after the healing protocol). The results show that thermal ageing alters the material's structure. Changes in glass transition and decomposition temperatures were also observed. Structural changes caused by thermal ageing resulted in variations in the measured infrared spectra. The self-healing ability also decreased as thermal ageing was applied to the sample. The obtained results will help to determine the limited conditions under which the tested material can be used while maintaining its self-healing ability.