Design of self‑healing biodegradable polymers

A biodegradable thermoplastic polymer has been formulated by solubilizing Murexide (M) salts in a commercial biodegradable vinyl alcohol copolymer (HVA). The Murexide has been employed as a self-healing fller with the aim to impart the auto-repair ability to the formulated material. Three diferent percentages (1, 3, and 5 mass%) of fller have been solubilized in HVA to evaluate the efect of the fller concentration on the thermal and self-healing properties of the resulting polymeric materials. The samples have been thermally characterized by Diferential Scanning Calorimetry (DSC) and Thermogravimetric Analyses (TGA), while their self-healing ability has been evaluated through the estimation of the storage modulus recovery, measured by Dynamic Mechanical Analysis (DMA). The results of DSC analysis have highlighted that the increase of the amount of Murexide anticipates the thermal events such as glass transition, crystallization and melting. TGA measurements have evidenced that, although there is a reduction of thermal stability of the materials in the presence of a high concentration of M, the polymer still remains stable up to 270 °C. Healing efciency higher than 80%, at a temperature beyond 60 °C, has been detected for the samples loaded with 3 and 5 mass% of Murexide, thus confrming the efcacy of this compound as an auto-repair agent and the relationship between the self-healing efciency and its amount. For a temperature lower than 70 °C, the healing tests, carried out at diferent values of tensile deformation frequency, have highlighted a frequency-dependent healing efciency. This dependence becomes negligible at higher temperatures for which the healing efciency approaches the value of 100%.