Effect Of C₃₆ Polyol On Controlled-Release Property Of Vegetable Oil Coating Material

In order to study effect of dimeric fatty acid polyol(namely C₃₆ polyol)on controlled-release property of vegetable oil coating material named C₁₈ polyol,the C₁₈polyol was used as base coating material and C₃₆ polyol as additives to produce modified coating materials.The static water incubation was used to test the release rate and longevity of the coated fertilizers before and after impacting treatment to evaluate the controlled release property of the C₃₆ polyol and to discuss influences of the ratios,dosages and optimal formula of the base and additives on controlled-release properties of coated fertilizers.The main research results were as followings.1.The slow and controlled-release effects of the coated urea was significantly affected by both of the proportion of C₃₆ to C₁₈ applied to produce coated urea.When the ratio of C₃₆ to C₁₈ was 2 to 3,no significant differences in preliminary solubility rate and differential solubility of coated urea were observed compared to control?PCU1?,and the appearances of the coated urea was glossy and scattering without caking.Furthermore,the coated urea fertilizer swelled after absorption of water,diameter of the coated urea increased with out burst and the surface area of coated fertilizer PCU3 raised by 23%after incubation compared to PCU1.That was to say,the C₃₆ was significantly increased the flexible of the coating layer.2.The authors of the paper proposed the longevity retention rate?t _R?of coated fertilizer,expressed as longevity of the coated fertilizer after impacting divided by the longevity of the coated fertilizer without impacting.The t _R was applied to evaluate the ability of maintain the longevity of coated fertilizer under condition of strong crashing.The research results suggested that rational application of C₃₆ polyol to C₁₈ with a ratio of 2:3could significantly improved the property of flexibility of the coating layer,and the longevity retention rate?t _R?of coated urea by use of the modified coating materials could be as high as 88%,which was 2.5 times higher than that of the control?PCU1?.3.The controlled-release property of the coating compound fertilizer was significantly affected by both of the proportion of C₃₆ to C₁₈ and the amount of the modified coating materials applied to produce coated compound fertilizer.When the ratio of C₃₆ to C₁₈ was 2to 3,and the integrality of the coating and longevity of coated compound fertilizer were optimal compared to the ratio of C₃₆ to C₁₈ was 1 to 2 and 1 to 1.The long effectiveness of the coated compound fertilizer increased with the increase of coating material.When the amount of coating materials was 3%,no significant differences in preliminary solubility rate and differential solubility of coated compound fertilizer were observed compared to control,but the longevity was less than the control.When the amount of coating materials was 4%,the slow controlled-release property was no significant differences.However,when the amount of coating materials increased to 5%,preliminary solubility of vegetable oil coated compound fertilizer modified by C₃₆ polyol was less than the control one,and differential solubility was no significant differences between the two coating,but the longevity of the former was 96.5 d,which was 13 d prolonger than that of the control.4.The slow and controlled-release property of C₃₆ polyol with C₁₈ polyol according to the ratio of 2:3 mixed and polymerized to produce coated urea was significantly affected by the synthesis condition of C₃₆ polyol.Orthogonal design test results showed that the B5formula was best formula,and preliminary solubility rate and differential solubility of B5applied to produce coated urea were minimal,coated complete,the longevity longest.5.Between 2.5%and 5.0%of the coating materials,preliminary solubility and differential solubility of B5 coating material applied to produce coated urea were significantly less than the control,the longevity?32.71⁹2.65 d?was significantly greater than of the control?13.78⁸0.78 d?.While,when B5 coating material reduced by 0.5%coating,the coating material could be applied to produce coated release fertilizer as coated by vegetable oil.The surface area of coated fertilizer compared with coated by B5 coating material increased and no burst.When the amount of coating materials was 5%,the surface area of coated fertilizer after swelling was increased by 44%in average compared to that of the control.The longevity retention rate?t _R?of B5 coating material coated urea after impacting was from 86.88%to 93.80%and significantly greater than that of vegetable oil coating material?from 46.15%to 89.58%?.The results showed that the modified coating materials of optimal B5 had good toughness and possessed ability to maintain the original longevity of the coated fertilizer after impacting.6.Among four kinetics equations of Richards equation,Logistic equation,Bertalanffy equation and first order kinetics equation,Richards equation fitted to describe the nutrient release characteristics of the coated control fertilizer with the highest correlation coefficient r and lowest standard error S.E.The correlationship was not affected by modified coating materials C₃₆ and coated thickness.Meanwhile,four characteristic parameters of the Richards equation could accurately and detailedly describe nutrient release properties and controlled-release property of the coated fertilizer.Therefore,Richard equation was the most suitable one to fit nutrient release trait curve of coated fertilizer by use of modified coating materials.