Influence of Various Types of Ageing on the Properties of Self-Healing Carboxylated Nitrile Rubber

Self-healing polymers, such as carboxylated nitrile rubber (XNBR), represent a promising solution for the failure of materials under mechanical and electrical loads. Self-healing materials can also be considered in this context as materials that are less predisposed to ageing under service conditions. This paper summarises the results of the XNBR testing via dynamical mechanical analysis (DMA), broadband dielectric spectroscopy (BDS) and Fourier transform infrared spectroscopy (FT-IR). UV (ultraviolet) ageing experiments were performed, and these methods evaluated the ageing effects on the tested XNBR. Then, the results were compared with the thermal ageing results that had already been reported. It was found that thermal ageing causes significant changes in material properties. The thermal ageing results show a slight increase in glass transition temperature. BDS analysis also showed deterioration of dielectric properties with ageing, including a noticeable decrease in dielectric constant and an increase in dissipation factor. Furthermore, it was found that UV radiation mainly affects the properties of the surface layer, the formation of which theoretically inhibits internal degradation. UV exposure gradually changes the mechanical properties measured by DMA, causing the storage modulus to almost double. In addition, changes in the FT-IR vibrational spectrum were observed, specifically damping of the peak in the region with a maximum of 1544 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> and 920 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup>. These findings are crucial for material selection and assessment of self-healing efficiency along accelerated ageing.