All-Natural Plant-Derived Polyurethane as a Substitute of a Petroleum-Based Polymer Coating Material

The development of efficient, biobased polyurethane controlled-release fertilizers from sustainable and eco-friendly biomaterials has received increased research attention, owing to concerns regarding global food security and environmental sustainability. Most previous studies focused on replacing petroleum-based polyols with biopolyols; however, the other main raw material, isocyanate, remained a petrochemical product. Herein, all-natural, plant-derived polyurethane-coated urea was successfully developed using castor oil and biobased isocyanate, and the performance of the coating shell before and after modification was compared. The results showed that the incorporation of a low dose of lauric acid copper into the coating material simultaneously enhanced the hydrophobicity and elasticity of the all-biobased polyurethane membrane, which prolonged the nitrogen release longevity from 3 to 112 days. In addition, the modified membrane showed excellent biodegradability in a soil environment. The novel all-biobased polyurethane coating material and modification technique provide insight for developing sustainable and eco-friendly controlled-release fertilizers.