Studies On Preparation And Properties Of Polyurethane-based Nanocomposite Coated Fertilizers

Fertilizers play an important role in ensuring food security.Traditional chemical fertilizers are quickly dissolved in water and cannot meet the fertilizer requirements of various growth and development stages of crops,resulting in low utilization rate of fertilizers.Therefore,improving fertilizer utilization is related to major issues of food security.The emergence of coated controlled release fertilizers overcome the above problems,which not only improve the utilization rate of fertilizers,but also effectively reduce the volatilization and loss of chemical fertilizer leaching,and economize fertilizer resources.The aim of this study was to synthesize a novel coated controlled release fertilizers,which was prepared by the addition nanomaterials into the conventional polyurethane coating material.The nanomaterials used in this paper are low cost,degradable nano-montmorillonite（MMT）and nano-polytetrafluoroethylene（PTFE）with excellent water resistance.MMT and PTFE were separately incorporated into polyurethane coating to synthesize polyurethane-based nanocomposite coating material,and the fertilizers were coated by solution soaking to obtain polyurethane-based nanocomposites with good controlled release properties.The coated controlled release fertilizer was characterized by a series of infrared spectroscopy,thermal properties,nutrient release properties and scanning electron microscopy for the properties and microstructure of the coating material.（1）The coating materials were synthesized by modified PTFE polyurethane to improve the properties of the coating material,and the fertilizer particles were coated to obtain the polyurethane/PTFE nanocomposite coated controlled release fertilizers.The chemical structure and microstructure of the prepared samples were determined by SEM,EDS and FTIR.The nutrient release rate of polyurethane/PTFE nanocomposite coated controlled release fertilizers in water was studied.The results show that compared with PU,the water absorption of the PTFE modified polyurethane-based nanocomposite coating material（PPU30）was reduced by 68.2%,the porosity of the coating material was reduced by 37.6%,and the thermal stability of PPU30 was increased by 27.6℃(T_50%).The water contact angle of the material surface was also increased by 15.7°.In addition,PPU has a better nutrient release characteristics than that of PU,and PPU30 has a 3.5-fold longer nitrogen release longevity than that of PU.Therefore,PPU30 provides a new method for the development and application of new coated controlled release fertilizers in agriculture and garden production.（2）The MMT,PM-200 and polyether polyol were used to synthesize the coating material,and the fertilizer granules were coated to obtain the polyurethane/MMT nanocomposite coated controlled release fertilizers.MMT was used to improve the performance of coating materials and improve fertilizer utilization.The MPUs coating materials were characterized by SEM,EDS,FTIR,XPS,TEM and XRD to analyze chemical structure and observe morphology.The nutrient release properties of polyurethane/MMT nanocomposite coated controlled release fertilizer was determined.According to the analysis results,compared with PU,the water contact angle of the surface of the MMT modified polyurethane-based nanocomposite coating material（MPU5）was increased by 20.1°,the porosity of the coating material was decreased by 30.0%,and the water absorption of the film material was decreased by 65.7%.The thermal stability was improved by 13K(T_max).In addition,MPU exhibited better nutrient controlled release properties than that of PU,especially MPU5 has a longer nitrogen release longevity than that of PU.Therefore,MPU5 with excellent controlled release performance can provide ideas for the development of novel nanocomposite coated controlled release fertilizers.