高吸水性树脂包膜尿素的结构特征及养分控/缓释性能

 【目的】研究高吸水性树脂包膜尿素的结构特征及养分控/缓释性能。【方法】以不同类型和吸水倍率的高吸水性树脂为包膜材料，以大颗粒尿素和改性矿物包膜尿素为原料肥料，研制出高吸水性树脂单层包膜尿素、高吸水性树脂复式包膜尿素系列产品，利用电子扫描电镜研究了其结构特征，并以水中溶出率法和模拟土柱淋溶法研究其养分释放特性。【结果】高吸水性树脂包膜尿素水中24 h氮素溶出率在18.22%～83.87%之间，土壤中4周氮素累积淋出率在40.91%～65.38%之间，较尿素降低5.21%～40.68%。控/缓释性能与高吸水性树脂的类型、吸水倍率及用量有关。聚丙烯酰胺型高吸水性树脂包膜尿素控/缓释效果好于交联聚丙烯酸盐型高吸水性树脂包膜尿素。随着高吸水性树脂用量的增加，高吸水性树脂包膜尿素的水中溶出率和土壤淋出率均明显下降；扫描电镜图显示高吸水性树脂复式包膜尿素的包膜效果明显优于高吸水性树脂单层包膜尿素，其控/缓释效果还与内膜材料有关。高吸水性树脂包膜尿素的内外膜均是由大小不一形状不规则的包膜材料微粒无序紧密堆积，并由胶粘剂填充空隙胶联而成，包膜叠层间和叠层内有微小孔隙,它们是尿素溶出的通道。【结论】高吸水性树脂包膜尿素兼具吸水、保水和养分控/缓释性能，是具有较好开发和应用前景的保水型控/缓释肥料。

Structure and Nutrient Controlled/Slow Release Characteristics of Super Absorbent Polymer Coated Urea

ObjectiveThe structure and nutrient controlled/slow release characteristics of super absorbent polymer (SAP) coated urea (SAPCU) was studied. Method A series of products of SAPCUs with single membrane of SAP or with duplex membranes of modified mineral inside and SAP outside were developed by using different types and different water absorbent rates of SAPs as coating material,and large granule urea and modified mineral coated urea (ZECU and PRCU) as core fertilizers. The structure of fertilizers was studied by Scaning Electronic Microscopy (SEM),and the nutrient release characteristics were studied using water dissolution rate method and soil column leaching method.ResultThe 24 hours N water dissolution rates of SAPCUs were 18.22%-83.87%,and N accumulated leaching rates in four weeks were 40.91%-65.38%,which decreased by 5.21%-40.68% compared with that of urea under the same experiment conditions. The capabilities in nutrient controlled/slow release were related to types,water absorbent rates and coating rates of SAP. Urea coated with copolymer of polyacrylamide and polyacrylate had greater capabilities than those with polyacrylate. Both of water and soil dissolution rates of SAPCUs decreased obviously along with the increase of SAP coating rate. However,SAPCUs with duplex membranes had much better effects on nutrient controlled/slow releasethan those with single membrane,and the effects were also related to materials of inner membrane. Stereoscan photographs showed that both the inner and outer coating membranes of SAPCUs were formed by different size and shape micro particles of coating materials,which were closely stacked at random. Furthermore,adhesive cemented the particles and filled up the gaps among them,but there were still micro holes,which served as the channels for urea dissolving out,in and between the stacking layers. ConclusionSAPCUs are new types of controlled/slow release fertilizers with the function of water retaining,and have promising prospect of development and application.