Fabrication of self‐healable thermoplastic polyurethane by masterbatch technology

This paper reports development of self-healable thermoplastic polyurethane (TPU) compound through the mixing of masterbatches of TPU and EVA (poly [ethylene-co-vinyl acetate]) (EVA) having various mole compositions. The aim was to promote a limited chemical interaction between TPU and EVA in the pristine compound that can enhance viscoelastic flow across the cut surface for autonomic healing. The healing was externally stimulated through microwave irradiation and the healing efficiency was determined from changes in tensile properties and complemented by image analysis. Infrared spectroscopy was used to detect TPU-EVA crosslinking in the TPU compound, which was further delineated from viscoelastic and swelling results. Tensile properties demonstrated a drop in tensile modulus, strength, and elongation at break than original TPU on increasing EVA concentration, but those, at the same time, were retained until the fifth healing cycles with higher EVA concentration in the masterbatch. The healing mechanism was attributed to the destruction of the hard domain in TPU leading to a marked increase in viscoelastic mobility at the interface of the cut section. The pristine TPU modified with higher amount of EVA in the masterbatch exhibited the highest range of healing efficiency (sample CC0-93%, sample BB0-97%, respectively)), reinstated the hypothesis of mixing a higher amount of EVA to promote autonomic healing. EVA based TPU compounds with superior self-healing property makes them an ideal candidate for applications in cable insulation and shape-memory devices.