农作物秸秆合成树脂包膜肥料的成膜及控释机理研究

The coating materials from biodegradable polyurethane (PU) synthesized by the wasted crop straw that have the advantages of cost reduction and biodegradability, achieving the sustainable developments of coated controlled release fertilizers. We get straw polyols by liquefaction technology and then by coating technique to spray onto the surface of fertilizers granule, finally we get PU coated controlled release fertilizers with smooth surface and high density in the program. We adjust controlled release ability of the coating materials on fertilizers which release their nutrient contents in accordance with the nutrient requirement of plants by screening the microstructure, thickness of the coating materials, additive types and combination. We discuss the physicochemical property, controlled release ability, and degradation conversion process in soil of PU coating materials by indoor tests, pot、field experiments, integration with polymers analysis technologies including scanning electronic microscope, infrared spectra, and nuclear magnetic resonance. Thus we explicate the filming of PU coating materials and controlled release mechanism of nutrient to further assess their feasibility and safety of agricultural use. The design idea of synthesis of PU coating materials from natural resources exhibits distinctive innovation, which is a new way to study environment-friendly coating materials with controlled release property. This provides a new approach and theoretical support for exploring the coated controlled release fertilizers with low cost and biodegradability.

以废弃的农作物秸秆为主要原料，合成可降解树脂聚氨酯（PU）作为包膜材料，不但能降低成本，而且能生物降解，实现包膜控释肥的可持续发展。本项目拟通过液化技术制得秸秆多元醇，采用包膜工艺将其喷涂到肥料颗粒表面，得到表面光滑、致密度较高的PU包膜控释肥。利用PU膜材料的微观结构、膜厚度以及添加剂种类和添加比例组合的筛选，调控包膜材料对肥料的控释能力，使其养分的释放与作物的需肥规律相吻合。拟采用室内模拟实验以及盆栽和田间试验，结合扫描电镜、红外光谱、核磁共振等高分子分析手段，研究PU包膜材料的物理化学性能、养分控释性能以及残膜在土壤中的降解转化过程，从而明确PU成膜性和养分控释机理，并进一步对其农用可行性和安全性进行综合评价。这种以可再生资源为主要原料合成PU包膜材料的设计思路具有鲜明的创新性，是研究环境友好型控释包膜材料的一条崭新途径，为开发价格低廉、易降解的包膜控释肥提供新思路和理论支持。

农作物秸秆合成聚氨酯（PU）树脂包膜控释肥的研究与开发，对实现包膜控释肥的可持续发展具有重要意义。本研究通过热化学液化技术制得秸秆多元醇，采用包膜工艺将其喷涂到肥料颗粒表面，获得了表面光滑、致密度较高的PU包膜控释肥。本研究采用室内模拟试验、盆栽和田间试验，结合扫描电镜、红外光谱、核磁共振等高分子分析手段，研究了农作物秸秆的液化过程及机理，测定了PU包膜材料的微观结构和性能，阐明了PU包膜控释肥的养分控释特征及机理，探讨了树脂残膜在土壤中的降解及其对土壤性质和油菜生长的影响。结果表明：（1）农作物秸秆在催化剂作用下，首先降解为分子量和分子链都相对较小的小分子化合物，然后再与液化剂发生酯化、醇解等化学反应，制得了秸秆多元醇，并明确了农作物秸秆的液化机理。（2）PU包膜材料具有致密、均匀的结构，优异的成膜性和养分控释性能；PU包膜控释肥在25°C水中的养分释放期为110 d，养分释放曲线呈现“S”型，与土壤中养分释放特征基本相类似。（3）明确了树脂残膜在土壤中降解转化的形貌变化，PU树脂残膜在土壤中具有明显的降解趋势，并且残膜残留对土壤性质无任何影响，且有利于油菜的生长发育。通过对PU包膜控释肥成膜质量、养分控释质量、肥效以及环境效应等进行研究，从而建立PU包膜控释肥综合评价体系，为PU树脂包膜控释肥的开发应用和大面积推广提供理论依据。