C36多元醇改良C18多元醇包膜肥料缓控释性能

为探讨C36多元醇(简称C36)对C18多元醇(简称C18,对照)包膜材料缓控释性能的影响,该文以C18为对照膜材,将C36与C18分别按照质量比1:2、2:3、1:1共混聚合制备成3种新型包膜材料,在相同工艺下依次制造成包膜厚度均为2.5%(膜材占核芯肥料的百分比)的包膜尿素,分别记作PCU1、PCU2、PCU3、PCU4,其中PCU1为对照。通过坠落撞击前、后包膜尿素的释放率评价C36作为包膜材料的效果。研究结果表明:C36与C18共混聚合包膜尿素的外观及耐撞击性能明显优于对照处理的,表现为包膜层光泽明亮、膜质均匀、膜层韧性好,同期静水培养的颗粒表面积较对照的增加了23%。该文提出了肥效期保持率(tR)的概念,并用其评价包膜肥料耐撞击性能。共混聚合物C36:C18比例为2:3时,包膜尿素耐撞击性能最优,受撞击后肥效期保持率tR可高达88%左右,为对照处理的2.5倍以上。该处理包膜尿素的初期溶出率、微分溶出率最小,与对照PCU1处理的无明显差异。C36嵌入C18共混聚合生成的新包膜材料对包膜尿素肥效期的影响与两者的比例和包膜材料的用量有关,当C36:C18为2:3,包膜材料用量(2.5%)小于常规用量(3%~4%)时,虽然包膜尿素的肥效期没有延长,但是包膜完整、膜层均匀、韧性强,在包膜肥受到强烈撞击的情况下能够很好地保持原有肥料的肥效期,即能保持包膜肥料的缓控释性能。因此,在C18多元醇嵌入适量C36多元醇是改良C18多元醇包膜材料,增加其包膜肥肥效期保持率的有效方法。

Slow and controlled-release property of C18 polyol coated urea modified by C36 polyol

Abstract: In order to study the slow and controlled-release properties of dimeric fatty acid polyol (namely C36 polyol) on C18 polyol (considering as conventional coating material consisting of castor oil and soybean oil) and its potential application value as coating material, C18 polyol was used as co-coating material mixed and polymerized with C36 polyol by 1:2, 2:3, 1:1 proportion to produce three kinds of new C36 coating materials (NC36). Three kinds of NC36 and the conventional coating materials were used to manufacture four types coated urea as slow and controlled-release urea, named PCU1, PCU2, PCU3 and PCU4. The PCU1 was the control. The average coating thickness is 2.5%, calculated by mass percentage of coating material out of substrate. The pure water incubation and refractive index method was used to test the release rate and longevity of the slow and controlled-release urea before and after impacting test to evaluate the controlled release property of the C36 polyol. The results showed that the appearances of the coating for the three NC36 were homogeneous and smooth, and the coating exhibited more flexible compared to the coating of the conventional coating material (PCU1). Furthermore, the surface area of coated fertilizer particle of PCU3 after incubation was increased by 23% in average compared to PCU1. The longevity retention rate (tR) of coated fertilizer, expressed as longevity of the coated fertilizer after impacting 20 times divided by that without impacting, was applied to evaluate the controlled release property of the new coating material. The longevity retention rate(tR) of coated urea by use of the new material could be as high as 88%, which was 2.5 times higher than that of the control. When the ratio of C36 to C18 was 2 to 3 (PCU3), no significant differences in preliminary solubility rate and differential solubility of coated urea were observed compared to control, and coated urea possessed the best ability to resist the impacting to reduce the longevity under this condition. However, when the ratio of C36 to C18 beyond 2 to 3, the initial and differential release rate of coated urea were lower than that of control. The nutrient release period or the longevity of the coated urea was significantly affected by both of the proportion of C36 to C18 and the amount of the new coating material applied to produce coated urea. Although the initial and differential release rate of the controlled release urea was not influenced by adding C36 to C18 with a ratio of 2:3. The coating layer of the mixture polymerid coating material was homogeneous and more flexible shown by significant increase of diameter of the coated urea exposed to water. However, the longevity was not lasted when the amount of coating material applied was less than conventional 3% to 4%. The research results suggested that rational application of C36 polyol to C18 with a ratio of 2:3 could significantly improved the property of flexibility of the coating and maintain the longevity of coated fertilizer under condition of strong crashing. It could be concluded that combination of C36 with C18 was an effective measure to improve the controlled release ability of the C18 and maintain longevity of coated urea when the fertilizer suffering strong impacting.