Polyurethane-Coated Urea Fertilizers Derived from Vegetable Oils: Research Status and Outlook

Polymer coated fertilizers (PCFs) play a crucial role in the sustainable development of precision agriculture. However, conventional petroleum-based coating materials for PCFs are non-degradable and depend on non-renewable resources. Thus, biobased coatings, particularly those derived from vegetable oils, are promising alternatives. This review presents an innovative classification of vegetable oils based on their chemical structure, specifically whether they contain natural hydroxyl groups or require hydroxylation modification. By leveraging data from the Web of Science database, we systematically analyze the research progress of vegetable oil-based polyurethane coated urea from 2005 to 2024. Hydroxyl modification strategies for vegetable oils lacking natural hydroxyl groups are explored. Preparation processes and controlled-release properties of polyurethane coated urea made from both types of vegetable oils are included. Furthermore, aiming at potential coating defects, various modification strategies and their practical effects are evaluated in detail. These insights provide a systematic reference for raw material selection and formulation optimization of vegetable oil-based coated urea. While summarizing the key research achievements, this review comprehensively describes the future challenges faced by the practical application of vegetable oil-based polyurethanes in this field, and proposes potential breakthrough paths based on material innovation and process optimization.