The Influence Of Polymer Structure On Slow Release Performance Of Urea

Sharp growth of world population makes the increasing demand of food. In order to increase grain prodduction, using a lot of fertilizers has become one of people’s choices. Howerve, utilization ratio of conventional fertilizers is very low, and overuse of fertilizers will do great harm to environment. As to solve these problems, developing new types of fertilizer is ergent. Slow/controlled release fertilizer is one of the research hotspots.The release performance of polymer coated slow/controlled release fertilizers is closely related to the structure of polymer. This thesis mainiy discussed the structural factors’ effect on release performance of polymer coated slow/controlled release fertilizers, including crystalline properties, hydrophobic/hydrophilic character, flexibility of macromolecular chains. The main contents contain:(1) The influence of crystaline to the slow release performance of urea is studied. Taking polylactic acid as the research object, using different methods to film. It is found that the membranes made by tape casting using 200 mesh nylon filter cloth as upholder have no apparent pores and cracks, and the surface topography is good. Polylactic acid membranes with different crystallinity were made by controlling the time and temperature of heat treatment. Using homemade fertilizer release measurement device to test release performance of urea of polylactic acid membranes with different crystallinity. The result shows that crystallization is against to the release of urea. The quantitative relationship between crystaline of polylactic acid and accumulative releasing ratio of urea is got by fitting. The equation is Qw=a*tb+6.64334×t0.79776. "a" and "b" is related to crystalline "X". Set "X" as X-axis, "a" and "b" as Y-axis respectively, afer fitting, equations were got. Equations are "a=-0.07148X-3.30037", "b=1.71998*10-4X3-0.01382X2+0.38051X-3.05255".(2) The infiuence of hydrophobic/hydrophilic to the slow release performance of urea is studied. Polymers with different contents of hydroxyl or carboxyl were polymerized by solution polymerization method taking n-butyl methacrylate as main monomers. The results of urea slow-release experiments show that the introduction of hydroxyl and carboxyl make urea accumulative releasing ratio bigger. When the hydroxyl and carboxyl contents are the same, the carboxyl is more conducive to the release of urea, which shows that the increase of hydrophilic is beneficial to the release of urea. We can get different slow-release effect by change polymers’hydrophobic/ hydrophilic.(3) The influence of flexibility to the slow release performance of urea is studied. Polyacrylate with different contents of hydroxyl, carboxyl, ester group or phenyl were sytheised, making them have different chain flexibility. The results of urea slow-release experiments show that polyacrylate with longer, smaller lateral group is benifit to the release of urea. Relative to monosubstitution, asymmetric replace is not conducive to the release of urea. The decrease of flexibility go against to the release of urea, so we can control the release rate of urea by change polymers’flexibility.