Abstract The polyurethane coated urea (PCU) was prepared by coating granular urea with the coating material, which was composed of castor oil, chain extender, polymeric MDI and wax. The wax as the sealant of the porous polyurethane coating was used to regulate the nitrogen (N) release rate of PCU. The test of N release behavior showed that the controlled-release effect of PCU in soil was inferior to that in water. Compare the analysis results of the PCUs in water, in alkaline water and in soil respectively, it showed that the structure of PU coatings was almost unchanged after immersion in water, and alkaline water, but after being buried in soil, the wax was degraded by microorganisms in the soil. The degradation of the wax changed the roughness and hydrophilicity of the coating. Calculation from IR demonstrated a loss trend of wax similar to the N release trends within 30 days, and the wax in the PU coating with 8 wt% wax degradated about 38 wt% after the coating was buried in soil for 40 days. The work shows that the stability of coating materials in water cannot prove his stability in soil. In order to make the PCU supply N slowly for a longer time in soil, wax or sealants with higher stability in soil should be selected and applied to the polyurethane coating.

中文翻译：

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土壤中蜡的降解及其对聚氨酯包膜尿素氮释放行为的影响

摘要 由蓖麻油、扩链剂、聚合MDI和蜡组成的包衣材料对颗粒状尿素进行包衣制备聚氨酯包衣尿素(PCU)。使用蜡作为多孔聚氨酯涂层的密封剂来调节 PCU 的氮 (N) 释放速率。氮释放行为测试表明，PCU在土壤中的控释效果不如在水中。将PCUs分别在水中、碱性水中和土壤中的分析结果进行比较，发现PU涂层在浸泡在水中和碱性水中后的结构几乎没有变化，但埋入土壤后，蜡被降解。土壤中的微生物。蜡的降解改变了涂层的粗糙度和亲水性。IR 计算表明，蜡的损失趋势与 30 天内的氮释放趋势相似，含 8 wt% 蜡的 PU 涂层中的蜡在将涂层埋入土壤中 40 天后降解了约 38 wt%。研究表明，涂料在水中的稳定性并不能证明其在土壤中的稳定性。为了使PCU在土壤中缓慢供氮更长时间，应选择在土壤中稳定性较高的蜡或密封剂并涂在聚氨酯涂层上。