Structure and properties of bio-based polyurethane coatings for controlled-release fertilizer |
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Authors: | Yun Liao Bing Cao Li Liu Xiandong Wu Sheng Guo Changhui Mi Kaiwen Li Meng Wang |
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Affiliation: | 1. School of Chemistry and Chemical Engineering, University of South China, Hengyang, China;2. Institute of Plant Nutrition and Resource, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China;3. School of Nuclear Science and Technology, University of South China, Hengyang, China |
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Abstract: | Two kinds of bio-based polyurethane coatings for controlled-release urea were prepared by in-situ polymerization used castor oil and liquefied starch as raw materials, respectively. Scanning electron microscopy (SEM) showed that the section morphology of castor oil based polyurethane (Castor-PU) coating was uniform and dense, and that of liquefied starch based polyurethane (Starch-PU) coating had certain proportion of microporous. Infrared spectroscopy (IR) showed that the two coatings had typical urethane characteristic structure, but the difference was that the Starch-PU had obvious unreacted isocyanate structure. Differential scanning calorimetry (DSC) showed that the glass transition temperature of the two coatings was around 58°C, but the Castor-PU had a crystallization domain with obvious crystallization melting peak at 130°C. Thermogravimetric analysis (TG) showed that the thermal stability of Castor-PU was significantly higher than that of Starch-PU. The controlled-release property test showed that when the coating ratio was 2.8%, the nutrient release longevity of urea coated with Castor-PU was 49 days and that of urea coated with Starch-PU was 14 days. The reasons for the poor controlled-release performance of Starch-PU were analyzed, which probably caused by concentrated sulfuric acid and hydrophilic dispersant added in the liquefied starch. |
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Keywords: | applications biopolymers and renewable polymers surfaces and interfaces structure-property relationships polyurethane |
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