Polysulfone coating with starch addition in CRF formulation Original Research Article

Studies on the possibility of using of polysulfone as a coating for water soluble NPK granular fertilizer were performed. The coatings were formed from the polymer solutions by the phase inversion technique. The polymer concentration in the coating forming solution was 18 wt.%. As the polysulfone coatings are not biodegradable, the starch was added to facilitate the destruction of the polymeric coatings in soil. The influence of starch addition to the film forming solution on the porosity of coatings was examined. It was observed that the addition of modifying agent (starch) to the polymer solution influenced the release rate of NPK from encapsulated granules. The release rates of macroelements rose when the starch concentration in coating was higher. However, it was observed that in the case of multiple coating the polymer layer was thicker and more compact. After 5 h of dynamic test performed with a single coating formed from polysulfone solution with 0.5 wt% of starch it was found that almost 65% of the ammonium ions, 48.3% of phosphates and 40.3% of the potassium ions were released, whereas the test performed with a triple coating prepared from the same film forming solution showed that only 16% of the NH4+ ions, 11.8% of phosphates and 9.3% of the K+ ions were released.