Biodegradability of renewable waterborne polyurethane modified with vinyl-grafted gelatin by UV curing

Waterborne polyurethane (WPU) prepolymer with acrylate terminal was prepared by using hydroxyethyl acrylate as an end-capping agent. Modified gelatin (mGH) was prepared by grafting vinyl groups which were obtained from hydrolysis and condensation of vinyl trimethoxysilane onto the renewable natural polymer material cold-water fish skin gelatin. Due to the excellent biodegradability and mechanical properties of cold-water fish skin gelatin, mGH was introduced into the WPU backbone by covalent bonding to improve WPU comprehensive property. The vinyl groups in mGH and the acrylate ends in the WPU prepolymer were connected by UV curing to prepare biodegradable and renewable mGH/WPU chemical hybrid materials. The test results showed that the film-forming properties, the water resistance and thermal stability of WPU were improved by covalent bonding. Water contact angle increased from79.6° to 96.5°, and the maximum thermal degradation rate temperature increased from 340 to 400 °C. In addition, incorporation of mGH with high modulus improved the moduli and yield strength of WPU, in which the yield strength increased from 11.3 to 18.2 MPa. The degradation performance of mGH/WPU chemical hybrid materials was also evaluated that the degradation rate reached 68% in 0.6% lipase PBS solution and 56% in soil after 60 days. The study provides a novel polymerization method for preparing high biodegradable decorative coatings and prints of specialty metals, polymer plastics and certain types of woodware as well as medical scaffold materials. Graphical abstract