Preparation And Performance Of Waterborne Polyurethane Coated Fertilizer With Modified Castor Oil

Polyurethane has been widely used in coatings,adhesives and other fields because of its excellent mechanical properties,high quality of weatherability and better solvent resistance.However,the traditional solvent-based polyurethane due to the consumption of a large quantity of solvents,resulting in environmental pollution,its application is limited.The water-based polyurethane without solvent participation,greatly reduces the environmental hazards and has been widespread concern.But the water-based polyurethane also has defects of low solid content,long time of curing and film forming,poor water resistance.Castor oil is a kind of non-polar long chain fatty acid with double bond,hydroxyl and other active groups,which can replace polyether or polyester to synthesize water-based polyurethane.The synthetic polyurethane emulsion has stable property,good film-forming performance and potential degradation.Hence,this paper tends to use castor oil instead of part of the polyester to synthesize water-based polyurethane,and to study the properties of synthetic polyurethanes.In this paper,the main raw materials are castor oil(CO),polyethylene adipate diol(PEA),2,4-toluene diisocyanate(TDI).The castor oil based aqueous polyurethane emulsion was prepared by solvent method using 2,2-bis(hydroxymethyl)propionic acid(DMPA)as the hydrophilic chain extender and water as the dispersion medium,with castor oil instead of part of the polyester to participate in the reaction.And the emulsion was cured into film.By single factor experient to study the effects of R value,DMPA content,PEA / CO ratio on the performance of castor oil based waterborne polyurethane.The viscosity test,particle size test,solid content test,centrifugal stability test,water absorption test,infrared spectroscopy,thermal stability analysis and other test methods and characterization methods were analyzed.The results showed that the reaction conditions were as follows: the R value was 3-5,the content of DMPA was 9%-11%,and the ratio of PEA / C.O was 1/2-3/2.The effects of factors such as R value,DMPA content,PEA / C.O ratio and the factors on the degradation rate of castor oil based waterborne polyurethane films were studied by using the single factor experimental results.The results showed that the best reaction conditions were as follows: R value was 3,DMPA content was 9%,PEA / C.O ratio was 1/1.The degradation performance of castor oil based waterborne polyurethane films wasstudied by soil burial method..The results showed that the degradation performance of high humidity soil is higher than that of low humidity soil.The degradation performance of neutral soil is higher than that of acidic soil.The degradation rates of the films in high humidity and low humidity soil environments were 9.9% and 6.4%,respectively.The degradation rates of the films in acidic and neutral soil were 6.7% and 7.0%,respectively.The degradation performance of castor oil based waterborne polyurethane urea coatings was studied by water immersion method and soil burial method.The results of the study are as follows: The study of water immersion method shows that the initial dissolution rate of coated fertilizer is 28.4%,the cumulative release rate of nitrogen is 55.8%,and the cumulative release rate of nitrogen meets the national standard.The results of soil burial research showed that the degradation rate of high humidity soil is higher than that of low humidity soil.The degradation rate of neutral soil is higher than that of acidic soil.The cumulative release rates of coated urea in soils with high humidity and low humidity were 38.0% and 37.0%,respectively.The cumulative release rates of coated urea in acidic and neutral soils were37.0% and 35.7%,respectively.