Preparation of Slow-Release Coated Urea Based on C8-Maleic Anhydride Copolymer-Cured Epoxidized Soybean Oil

• Published in: Industrial & engineering chemistry research 2022-11, Vol.61 (45), p.16593-16601
• Main Authors: Zhai, Jiaxin, Zhang, Chen, Zhao, Changwen, Yang, Wantai
• Format: Article
• Language: English
• Subjects: Applied Chemistry
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/acs.iecr.2c01968

Coated fertilizers have the advantages of high nutrient utilization efficiency, long release duration, and low environmental pollution, which play an important role in sustainable agricultural development. Organic polymers are commonly used coating materials of coated fertilizers, but still have limitation of high cost and nondegradability. In this work, a method to prepare coated urea (CU) with slow nutrient release characteristics by curing biodegradable epoxidized soybean oil (ESO) with low-cost C8-maleic anhydride copolymer (C8-MA) was developed. The effects of curing temperature, anhydride/epoxy group ratio, and imidazole content on the curing reaction were investigated. The coating material (CME) prepared with the molar ratio of anhydride to epoxy of 1:1 and 5 wt % imidazole at 100 °C exhibited a contact angle of 81.9°, which is more hydrophobic than that of C8-MA (68.1°). The water absorption and coating porosity of the CME was 5.9% and 2.5%, respectively, implying an excellent water resistance property. Scanning electron microscopy images of CU showed that the urea granules were completely wrapped by the CME, which had intact structure and smooth surface. The CU showed a sustained release behavior and the steady release can last a period of >28 days.