A new UV-curable biodegradable waterborne polyurethane-acrylate based on natural rubber blended with cassava starch

An ecofriendly UV-curable biodegradable waterborne polyurethane acrylate (WPUA) was synthesized using hydroxy telechelic natural rubber (HTNR), gelatinized cassava starch (GCS) hexamethylene diisocyanate, hydroxymethyl propionic acid and 2-hydroxyethyl acrylate and Darocur 1173 (photo-initiator) for coating, adhesive applications, and so forth. WPUA thus prepared with a total solid content of about 20% had a good storage stability with a pot-life of 3 months. The UV-curable WPUA/GCS films showed superior photosensitivity with an irradiation time of 60 s. With increasing GCS content of the WPUA/GCS films, its transparency increased and surface gloss decreased. Scanning electron microscopic micrographs indicated good miscibility with strong interactions between WPUA and GSC in the matrix leading to high tensile strength and surface free energy with enhanced thermal degradation. Increasing the GCS content up to 75 wt% in the film accelerated its degradation under weathering aging, and showed complete disintegration in soil after 7 days. This work provided a new environmentally friendly pathway to prepare WPUA based on HTNR and GCS with good biodegradability.