Research progress of plant oil-based polyurethane coated fertilizer

Polyurethanes, the conventional coating materials used for slow-released fertilizer production, are mainly processed from petroleum-based raw materials. As the high cost and environmental risks of petroleum-based polyurethanes, bio-based polyurethanes have become the alternative coating materials in recent years. Among various bio-based materials, vegetable oil draws attention because of low price, wide source, non-toxicity and biodegradability. In this paper, we summarized the preparation methods of vegetable oil based polyols, the main categories of plant oil based polyurethane coating materials, the modification and application of slow release fertilizers coated with the plant oil based polyurethanes. The often used technologies for the procession of vegetable oil based polyols included epoxy ring-opening, transesterification, ammonolysis, hydroformylation and ozone REDOX. Such raw materials like acrylic ester, epoxy resin, silicone, fluorine modification, nanomaterials, etc. are often used for the modification of plant oil-based polyurethane coating films. Plant oil-based polyurethane coated fertilizer have been proved of advantages of reducing ammonia volatilization and nitrogen leaching, and improving nitrogen use efficiency. How to improve the degradability of plant oil-based polyurethane coating materials and the slow release capacity of fertilizer, increasing the crosslinking density of plant oil-based polyurethane, reduce the production cost, reveal the slow release mechanism and expand the application scenarios in the field trail are the focus of future research.