Preparation of Self-healing Natural Rubber/Polycaprolactone (NR/PCL) Blends

Abstract

The preparation of self-healing polymers for use following mechanical failure using commercial, bio-based polymers without complex synthesis and expensive healing reagents has been very rare. In this study two commercial, bio-based polymers, natural rubber (NR) and polycaprolactone (PCL), were melt-blended to form NR/PCL blends. To increase the healing efficiency via supramolecular hydrogen bonding interactions, various amounts of acrylic acid were grafted onto the PCL. The results showed that the healing efficiency of the blends in the self-healing test at 80°Cwas higher than for blends at 60?°C due to higher molecular mobility/diffusion resulting from the molecular motions above the melting temperature of PCL which was near 55?°C in all cases. The highest healing efficiency, 62.8%, was attained for the NR/PCL-g-4AA (40/60) blend containing 4 phr PCL of AA. In addition, with the application of the shape memory-assisted self-healing (SMASH) mechanism, the healing efficiency increased further, up to 79.9%. The high shape recovery ratio (>90%) helped the crack to close faster when the sample was heated to trigger the shape memory process, leading to the increased healing efficiency in comparison with the sample without the shape memory process triggered by heating. To the best of the authors’ knowledge, there have been no similar works in the preparation of self-healing, bio-based polymer blends through the current approach so far. We suggest the synergistic effects of both the physical and chemical processes applied to commercial, bio-based polymers provide the chance of expanding the applications of these green polymers with additional functionality.