Preparation Of Vegetable Oil Based Controlled-release Urea Fertilizer And Study On Its Controlled-release Characteristic

Polyol with high hydroxyl value was prepared using epoxy ring opening.A novel bio-based polyurethane(PU)was synthesized by using isocyanate and vegetable oil based polyol for controlled-release fertilizers(CRFs).Soybean oil(SBO)and waste frying oil(WFO)based PU was modified by silicone and epoxy resin(EP)respectively for improving the controlled release characteristic.The modification aimed to expose hydrophobic silicon atom on the membrane surface through silicon modifying soybean oil based PU,and form a crosslinked interpenetrating network structure by using EP modifying waste frying oil-based PU.Many coated controlled-release urea were prepared by controlling the film thickness and modifier dosage.The shell and its controlled-release properties were tested.The main results are as follows:1.Soybean oil and waste frying oil can be successfully prepared into oil based polyol with high hydroxyl value through epoxy ring opening,and the reaction conditions are mild,low energy consumption and high efficiency.When the molar ratio of double bond,H2O2,CH3 COOH is 1:2:1.5,the reaction temperature is 65 oC,the rotation rate speed is 200 rpm,the reaction time is 4 ~ 5h.2.FTIR and SEM measurement showed that silicone was successfully grafted on soybean oil based PU in this experiment.Silicone can improve the thermal stability of the coating,reduce the porosity and improve water contact angle of coating,the water contact angle of soybean oil based PU modified by 0,10,20 and 40% silicone respectively were 64,90,104 and 112 o,while the corresponding porosity is respectively 16.07,12.33,11.18 and 10.08%.The N release characteristics of the PU-coated ureas(PCUs)in water were determined at 25 ±0.5oC.Experimental results showed that the presence of HTMS in the PUs slowed the nutrient release from the PCUs.When the amount of coating material was increased from 3% to 7%,and the amount of silicone was increased from 0% to 10%,the release longevity increased from 7.5 to 70 days.3.EP can increase cross-linking chain and the crosslinking density of frying oil based PU significantly,reduce the proportion of hanging chain proportion,the crosslinking density of 10,20% E44 modified PU were increased 82.5 and 77.9% than unmodified PU,respectively.The SEM showed that surface of the EP/PU coating was more compact,more smooth.EP can significantly affect the water absorption rate of the film,the absorption rate(third days)of 10% E44 modified PU decreased from 12.3% to 6.5%.Porosity of 0,5,10,20,50 and 80% E44 modified PU were 10.0,8.5,7.2,7.9,10.4 and 15.3%.The cumulative N release curves for EP-modified PCUs showed an “S” shape,more consistent with the need of crop fertilizer needed for growth.4.The vegetable oil-based polyurethane films are biodegradable.The degradability of 0,10 and 20% EP modified PU were measured.The weight of 0,10 and 20% EP modified PU coatings reduced by 31.2,29.1 and 20.3% after 210 days of degradation in soils,respectively.As can be seen from SEM,large holes of coatings were gradually formed in the degradation process,which may be due to some chemical bonds of polymers can be fractured in the soil environment.