Preparation And Evaluation Of Controlled Release Fertilizer Coated By Polyurethaane

With the exponential growth of the global population, the agricultural sector is bound to use more and more fertilizers to increase grain production. Traditional urea fertilization, not only leads to the low utilization ratio, but also causes environment and climate change. It is reported that the coated urea can effectively deal with this problem and the polymer is the favoring coating material. The direction and goal of the current research aims to reduce the cost of polymer coated urea and ensure the controlled release properties, to meet the utilization of plant at different growth stages, as well as minimize the harm of coating material on the soil environment.Here two different modification methods were used to optimize the polyurethane coating, such as composite with mesoporous silicas and swapping coating of different types of polyurethane. SBA-15 mesoporous silicas with four morphologies were synthesized and characterized by XRD, SEM, TEM, BET and FTIR. Polyurethane/SBA-15 composites were prepared via an in-situ reactive-layer spray technique on urea granules. The effects on SBA-15 on structure and controlled release performance of coating were elucidated and compared to n-SiO2. The results showed that rod-like calcined SBA-15 with an average particle size of 700 nm extremely improved the release properties of PU at the filler loading of 1%. The release duration can be doubled to 70 days from 35 days of pure polyurethane coating.Polyurethane coated urea with polyester/polyether type polyurethane swap films was prepared. The wet ability, thermal stability and morphology of the obtained films were characterized by contact angle, TG and SEM methods. The results show that the hydrophobicity of polyester type polyurethane is lower that of polyether type polyurethane but the thermal stability is higher. Coating order of polyester type and polyether type polyurethanes exactly has impacts on the controlled release performance of the coated urea, when polyester type polyurethane is used as outer and polyether type polyurethane is used as inner, the controlled release property is more excellent. When the coating ratio of polyester type and polyether type polyurethane is 1.5:1.5, the release duration is as long as 84 days.