Study On Preparation And Properties Of Slow-Release Fertilizer

This thesis mainly researched slow-release fertilizer which was prepared matrix of starch/PVA blends and urea. Control degradation in the environment of starch and PVA in order to control the rate of fertilizer into the environment and absorption by plants. It achieved purposes which did not pollute the environment, and improved fertilizer use efficiency.It was based on blending technology, and glycerol, polyethylene glycol (PEG) and water as plasticizers. It investigated the effect of type and addition of plasticizer on mechanical properties, flow performance and the cumulative release rate of urea of slow release fertilizer.For the slow-release fertilizer using glycerol/water as composite plasticizer, it mainly studied of the effect the amount of water of glycerol/water complex plasticizer, ratio of glycerol/water composite plasticizer, ratio of starch/PVA and the amount of urea on rheological properties, mechanical properties and the slow release properties. The results showed that, as PVA content increased, the tensile strength and rheological properties of slow release fertilizer both increased. With the increase of water content, the tensile strength decreased, and rheological properties of slow-release fertilizer increased. The optimal formula is starch50phr, PVA50phr, glycerol20phr, water20phr, urea50phr.For the slow-release fertilizer using PEG/water as composite plasticizer, it studied the effect molecular weight of PEG, the amount of PEG/water composite plasticizer on rheological properties and the slow release properties. The results showed, with PEG molecular weight increasesed, the tensile strength increasesed, elongation at break of slow release fertilizer decreased, and shear viscosity and cumulative release rate increasesed. While increased the amount of composite plasticizer, the tensile strength of the sample firstly increased and then decreased, and the cumulative release of slow-release fertilizer rate decreased. When the PEG molecular weight was1500, the amount of composite plasticizer was40phr, the comprehensive performance of slow-release fertilizer was excellent.For slow-release fertilizer adding clay, it adjusted the release effect by changing the clay quantity and adding method in the slow release fertilizer. The result showed that with the content of clay increasesed, the tensile strength firstly increased and then decreased. Adding method of ultrasound blend was reasonable.In this study, the structures of slow-release fertilizers were characterized by scanning electron microscopy.