Preparation of a Novel Economically Efficient and Environment Friendly Controlled Release Urea from Liquefied Corn Straw and Castor Oil

Because of the renewable nature of castor oil, it has been widely used in the production of bio-based polyurethane (BPU) coated controlled-release fertilizer. However, although castor oil (CO) is a natural material, the polyurethane prepared from castor oil is still a product difficult to degrade. In order to further improve the degradability of castor oil-based polyurethane, six different BPU coated controlled-release urea were prepared using liquefied corn straw (LCS)-based polyols, castor oil, isocyanate as raw materials, glycerol and acrylamide as crosslinking agents. The surface morphology, hydrophobicity, thermal stability, release characteristic curve, degradation related functional groups, colony, soil micro plastic content and other indicators of controlled-release urea were determined, and then six different controlled-release urea were comprehensively evaluated. The results showed that the release time of LCS based polyurethane coated urea was shorter than that of CO based polyurethane coated urea, but the degradation was better. The crosslinking structure significantly improved the hydrophobicity of BPU and prolonged the release period of controlled-release fertilizer. When 30% castor oil was replaced by liquefied corn straw, the release period remained unchanged, but the degradability was improved, which made the content of microplastics in soil decreased. In a word, the partial replacement of castor oil with liquefied corn straw and its application in the production of coated controlled release fertilizer have high environmental benefits.