有机硅改性秸秆合成树脂包膜超大颗粒控释肥养分释放调控机制的研究

Using straw synthetic resin as a substitute for non-renewable petroleum products as coating materials for controlled-release fertilizers provides great option for the development of high-efficiency, low-cost, and environmental-friendly fertilizers. Our preliminary research indicates that extra large fertilizer tablets coated with organic silicon modified straw synthetic resin possess characteristics of excellent controls on nutrient releases and low usage of coating materials. However, the mechanisms of controlling nutrient releases from extra large fertilizer tablets which were coated with organic silicon modified straw synthetic resin are not well understood. The proposal of this application is to (1) characterize the influx of water and the outflux of nutrients through the membrane of the modified straw resin by determining the distribution and state of the hydrophobic organic silicon compound on the membrane surface, within the membrane, and in the micro-pore channels; (2) understand the synergic effects of organic silicon modified straw synthetic resin membrane and extra large fertilizer tablets on the nature and behavior of controlling nutrient releases; and (3) reveal the mechanisms of controlling nutrient releases of extra large fertilizer tablets coated with organic silicon modified straw synthetic resin. The proposed research will ultimately provide both fundamental information and practical technology for the development and optimization of high-efficiency, low-cost, and environmental-friendly controlled-release fertilizers using straw synthetic resin.

利用农作物秸秆合成树脂包膜材料来替代资源不可再生的石化产品类包膜材料是研发高效、低成本、环保型控释肥料的发展方向。本申请在前期研究中明确了利用有机硅化合物改性秸秆合成树脂包膜的超大颗粒控释肥具备优良养分控释性能和节省膜材的特点，但是该有机硅改性秸秆合成树脂包膜超大颗粒控释肥养分控制释放的机理还不清楚。本项目拟通过研究疏水性有机硅化合物在秸秆合成树脂膜壳表面、膜材内以及微孔通道中的分布及存在状态，探讨其对水分进入膜内与养分溶出膜外的作用机制，并研究有机硅改性秸秆合成树脂膜和超大肥料颗粒共同对养分控释性能影响的叠加效应及其调控机制，揭示有机硅改性秸秆合成树脂包膜超大颗粒控释肥养分释放的控释机理，为完善利用农作物秸秆类物质合成树脂膜材，研发高效、低成本、环保型包膜控释肥提供理论与技术指导。

针对控释肥料的包膜材料主要来源于石化产品，存在价格高、资源不可再生、难降解等问题，本课题以生物基材料为原料制备了生物基聚氨酯包膜控释肥料，系统开展了生物基膜材的成膜机理、改性技术研究，取得了五个方面的创新成果：（1）确定了液化技术的最优参数，明确了生物基聚氨酯的成膜机理：经液化的生物基材料含有大量羟基，可与异氰酸酯聚合形成生物基聚氨酯膜材；（2）有机硅与生物基聚氨酯材料交联反应，增强了膜材的致密性和疏水性，减少了膜材孔隙和水分进入，证实了有机硅在膜壳上的存在和分布状态及其对膜微结构的影响；（3）在生物基膜材表面构建超疏水界面，在水和膜壳界面之间形成空气膜，水分子只能以气态扩散的方式缓慢通过膜壳，减缓了养分释放速率，揭示了膜壳表面上的有机硅对水分进入和养分溶出膜外的作用机制；（4）有机硅的疏水链在膜壳内部微孔通道中形成纳米粗糙结构，起到堵孔作用，同时截留空气，形成多层空气膜层，减缓了水分进入和养分释放，揭示了膜内及微孔通道中的有机硅对水分进入和养分溶出膜外的作用机制；（5）高压制备的超大颗粒尿素，比表面积减少三分之二，节省了膜材，探究了超大颗粒控释肥料溶胀和养分跨膜扩散的机理。综上，经有机硅改性的生物基聚氨酯控释肥料，与未改性的肥料产品相比，其膜材达到160°的超疏水状态，养分控释期延长3-4倍。此外，深入研究发现生物基多元醇中存在许多不参与反应成膜的杂质，这些杂质随膜内养分向外释放会被带出膜壳，在膜壳上留下孔洞，进而加快养分释放。因此，针对生物基材料的缺点，本课题还研发了多种改性技术（双改性、弹性增韧、磁性微球、纳米铜），并探究了其养分控释机制。综上所述，本课题为利用资源再生的生物基材料制备缓控释膜材提供了科学依据，为生物基包膜缓控释膜材的改性提供了理论与技术支撑，实现了生物基膜材替代石化类膜材的技术进步，将会促进生物基控释肥料的大规模发展与应用。