Self-healing modified liquefied lignocellulosic cross-linked bio-based polymer for controlled-release urea

Alkali-hydrolyzed lignocellulose was liquefied into polyols by acid-catalyzed dissolution, and then cross-linked with castor oil to prepare bio-based cross-linked polyurethane. Then, bis (2-hydroxyethyl) disulfide (SS) with self-healing function was used to reduce foaming in the curing process of polyurethane coating. Afterwards, disulfide bond modified cross-linked bio-based polyurethane coating (BCSPU) was applied to controlled-release urea (CRU). The results of excitation-emission matrices indicated that SS made the coating smoother and denser and preventing the release of non-film-forming substances. Cross-linking modification technology significantly extended the controlled release longevity of CRU by 77.3%, and the self-healing modification further prolonged the nitrogen release longevity by 61.5%. In addition, modified coating materials were non-toxic to wheat seeds and easily biodegradable in the soil. Cross-linking, self-healing modified controlled-release urea has enormous application potential in sustainable agriculture.