Preparation And Properties Of Coated Materials Used For Controlled Release Fertilizer

How to improve the utilization rate of fertilizer to prompt the sustainable development of agriculture has become the current hot spot. More and more people devote themselves to the study of slow/controlled release fertilizers. The research emphasis of this thesis is polymer coated materials, starting from the structure of the polymer membrane, explored the relationship between the stucture of polymer and penetration of fertilizer, so as to control the release of fertilizers by changing the membrane structure. The main contents contain:(1) Through solution and emulsion polymerization, a series of polymers with different functional groups, different contents of functional groups and different crosslinking degrees were polymerized using styrene, butyl acrylate as main monomers; hydroxyethyl acrylate, acrylamide, acrylic acid as functional monomers; divinyl benzene and N-methylol acrylamide as crosslinking monomer. Optimizing the processing technic of emulsion polymerization. The optimum conditions are seeded emulsion polymerization. Take continuous drip addition of monomers. The dosage of initiator is 1.0% of monomers(mass fraction, the same as below), the dosage of emulgator is 4%, the dosage of NaHCO3 is 0.25%, the dosage of 1-dodecanethiol is 0.2%. The best reaction temperature is 82℃, and best adding time of monomers is 3 h. Emulsion polymerized in these conditions can remain stable in a long time. The gel rate is 0, solid content is about 32%, and monomer conversion rate is more than 96.6%. The results of tensile tests show that elongation is between 104.5% and 107.5%. The toughness of membranes can meet the practical needs.(2) Using membranes with good surface topography and same thickness, urea slow-release experiments were carried out. Under the same combination of monomers, Urea’s accumulative releasing ratio got from membranes made by emulsion polymerization are much bigger than membranes made by solution polymerization. The introduction of functional monomer can change controlled release performance of membrane materials at some level. In emulsion polymerization, when the dosage of hydroxyethyl acrylate increase from 2% to 10%, urea’s accumulative releasing ratio rise from 31.08% to 38.07%. When the dosage of acrylamide increase from 2% to 10%, urea’s accumulative releasing ratio rise from 31.18% to 42.61%. when the dosage of acrylic acid increase from 2% to 10%, urea’s accumulative releasing ratio rise from 33.73% to 46.80%. When the dosage of N-methylol acrylamide increase from 0 to 5%, urea’s accumulative releasing ratio reduce from 30.95% to 6.56%. The introduction of hydroxyl, acylamino or carboxyl can change nutrient release rate and meet the requirements of different crops, as well as the changing of crosslinking degree.