Preparation And Characterization Of Organic And Inorganic Complexed Material With Water/Fertilizer Bifunctional Controlled-release Ability

Retaining agent, also known as super absorbent resin, is a kind of functional polymer materials. It is able to absorb to thousands of times its own weight water retention due to its structural reasons at the same time it also has the function of absorb fertilizers. Water and fertilizer are indispensable factors to increase agricultural production. Therefore, the research of water-retaining agent preparation and combine with fertilizer technology is of great significance for the sustainable development of agriculture in China.This thesis adopt the natural substances starch, and add a certain amount of the inorganic mineral soil and sodium carboxymethyl starch, use the acrylate monomers to synthesize composite water-retaining agent. Then take the envelope method to combine water-retaining agent and urea to make a kind of multi-functional fertilizers with water retaining and slow-release character. Systematically investigated starch gelatinization, reaction temperature, amount of monomer, amount of crosslinking agent and inorganic mineral soil dosage and then optimization. The polymer were characterized by infrared and SEM. Moreover, their various properties were investigate, such as liquid absorption, thermal stability, water retention ratio, repeat number of liquid-absorbent and so on. Urea coated with the retention absorbent and got optimization coating process with the sustained-release performance as the main indicator. The coating layer use infrared and electron microscopy to characterize and tested various properties. The main conclusions are as follows:1. Determined the conditions of starch gelatinization, obtained the composite water-retaining agent the best preparation process. The distilled water absorption ratio is1195.4g·g-1,0.9wt.%(weight percent) physiological saline absorbencies than90g·g-1.2. Water absorption rate, absorbencies, water retention capacity, thermal stability and other indicators were studied. The experiment results showed that when the pH value is between four and eight, water retention agent has good water absorbency. Calcium and magnesium ion have great impact on the absorbencies. When potassium chloride and ammonium chloride concentration at0.5mol·L-1, it’s absorbencies above60g-g"1. Water absorption has little change in the100℃temperature range. When the heating temperature reaches180℃, the water retention agent began to appear carbonization phenomenon. Water retaining agent after six times of repeated water absorption, the absorption rate for the first time in50%, has the capability for repeated use.3. Obtained the best envelope process of selection bentonite as inorganic coating materials, the amount of bentonite quality urea70%to100%, the amount used is5%to10%of the urea quality. The release properties of the coated urea the release rate is50%within12hour.