基于改性天然橡胶的保水型缓释复合肥料：制备与应用评价

In view of the problems existed in the Gansu province of drought, less precipitation and low utilization rate of fertilizer, to solve current problems of slow-release fertilizers of hard-degradation, unitary function and complicated technology, this program designed two kinds of modified natural rubber(MNR) and applied in slow-release fertilizer with the function of water retention. Natural rubber graft super absorbent resin was planned to prepare and used as coating of fertilizer. Natural rubber/super absorbent resin semi-IPN amphoteric superabsorbent was planned to synthesize and employed to prepare slow-release fertilizers by adsorption of ammonium and phosphate. The modified natural rubber materials and prepared slow-release fertilizers were to characterize. Degrable properties of MNR, slow-release properties and properties of water adsorption and water retention of the above mentioned slow-release compound fertilizers were to test. Further studies were to investigate effects of material structures on slow-release properties and properties of water adsorption and water retention. Explore controlled release mechanism of fertilizers and reveal the relationship between material structure and degradation, water adsorption, water retention properties. In order to creat a comprehensive evaluation mechanism, a potato pot experiment was to conducted to investigate the effects of slow-release compound fertilizers. Through the potted plant experiment and the empirical analysis, relationship between fertilizer and increasing crop yield was to study. The study results will provide a new theory and new way for MNR applied in controlled/slow-release fertilizers. The achievement of this research will develop the controlled/slow-release fertilizers technology of degradable, muti-function and industrial prospect.

针对甘肃地区降水少，旱地多，肥料利用率低的特点，解决当前缓释肥料难降解、功能单一、生产工艺复杂的问题，本项目拟通过接枝技术、半互穿网络聚合物技术对可完全降解的天然橡胶改性，使天然橡胶具备吸水保水性能，制备高吸水树脂接枝改性的天然橡胶以及天然橡胶/高吸水树脂半互穿网络聚合物材料。利用上述两种改性天然橡胶材料，分别采用包膜法、吸附法制得包膜型、吸附型保水缓释复合肥料。测试材料的降解性能，深入研究材料结构对其降解性能、缓释肥料的缓释性能及吸水保水性能的影响，揭示材料结构与性能的关系。将该缓释复合肥料应用于马铃薯盆栽试验，参考盆栽实验结果探讨肥料与作物增产关系，建立综合评价机制，筛选性能最佳的保水型缓释复合肥料。研究结果将为改性天然橡胶材料在缓释肥料中的应用提供一定的理论基础和关键制备技术，为开发可降解、多功能、有工业应用前景的缓/控释肥料提供新的思路。

天然橡胶是聚异戊二烯为主要成分的天然高分子，它具有较强的疏水性且易于成膜，是包膜化肥的理想材料。针对甘肃地区降水少，旱地多，肥料利用率低的特点，解决当前缓释肥料功能单一、生产工艺复杂的问题，本项目利用化学手段对天然橡胶分子进行改性，使其不但保留天然橡胶强度好、利于成膜等优点，又具有高吸水树脂的吸水保水特性，并将改性天然橡胶应用于肥料制备，获得多功能缓释复合肥。.首先，采用自由基溶液聚合法，制备了天然橡胶接枝丙烯酸（NR-g-PAA），优化了反应条件，提高了NR-g-PAA的吸水性能。通过一系列表征和测试，确定了NR-g-PAA的结构、形貌、热性能和生物降解性。用尿素、KH2PO4和凹凸棒土通过圆盘造粒制备了复合肥料内核。然后，以NR为内层包膜，NR-g-PAA为外层包膜，制备了包膜复合肥。研究了复合肥在土壤中的缓释行为。结果表明，NR-g-PAA具有纤维网络结构，其最大吸水率为744.00±14.38%，在酶存在的缓冲溶液中35天可降解29.94±0.65%。包膜肥料30天内N、P和K的释放率分别为54.35±1.49%、51.18±2.15%和44.37±1.38%， .其次，以天然橡胶胶乳为模板，设计合成了一种以天然橡胶接枝聚丙烯酸-丙烯酰胺[NR-g-P(AA-co-AM)]网络和线性聚二烯丙基二甲基氯化铵(PDADMAC)为基础的半互穿聚合物网络水凝胶NR-g-P(AA-co-AM)/PDADMAC。测定了水凝胶的结构、形貌、热性能、生物降解性能和吸水保水性能。并用水凝胶吸附铵制备多功能缓释肥料。研究了水凝胶的吸附行为以及肥料在土壤中的缓释特性。结果表明，水凝胶的结构和性质受PDADMAC含量影响，其吸水率最大为112.04±6.55g/g，此时材料具有薄孔壁的多孔聚合物网络结构。同时，在土壤中1.5%（质量分数）水凝胶时，土壤保水率可达115.62±2.08%。水凝胶对NH4+的最大吸附量为13.02mmol g-1。在土壤中包埋30天后，缓释肥料的氮含量剩余34.95±0.16%。.结果表明，本项目制备的缓释肥料的营养元素的释放可以持续30天以上，具有良好的缓释性能。项目研究开发了天然橡胶全新的应用途径，为改性天然橡胶材料在缓释肥料中的应用提供一定的理论基础和关键制备技术。项目首次提出并应用的天然橡胶乳液模板法，也为高分子材料合成提供了新的思路。