Preparation And Characterization Of Biodegradable Polymeric Membranes For Controlled-release Fertilizers

Cellulose Acetate (CA), starch and polyvinyl- alcohol (PVA),which are cheap and can be easily found were chosen to prepare one kind of membrane for coating the soluble granular fertilizer. It was investigated that the influences of many aspects on the membrane properties, and the method"dissolution rate in water" was used to study the nutrient controlled rlease effect of the two coated fertilizers. The results are as followed:(1) The CA envelope stuff was made with the L-S way. The envelope stuff's slow-release capacity to the fertilizer nutrient has a close relation to the membrane's aperture , porosity, the loosen degree within the aperture was indicated by experiment . The ideal conditions in making membranes is that: the mass compose of the solution which is used for making membranes:the polymer/the solvent=15/55, the content of the additive should not be over 20%. The evaporation time of the solvent should be 5-30min. The gel temperature should be 25℃. The nutrients preliminary solubility and the differential solubility of coated fertilizers is 14.1% and 2.36%,respectively. Cumulative nutrient releaseing can be described quantitatively by the first-degree reaction dynamic equation..(2) Starch and polyvinyl- alcohol (PVA) were chosen to prepare one kind of membrane for coating the soluble granular fertilizer. The controlled release fertilizerd with a better release diffusion performance could be prepared, when the ratio of the content of starch and PVA is 7:3, the content of formaldehyde is limited to the range of 10wt%. The XRD results shows that the crystal structure of PVA was changed after being cross-linked with starch, whose vice-bond was broken ,crystal was destroyed. The FT-IR explores the starch was linked with PVA by chemical binding,the cross-linking reaction results in an improvement of compatibility of the starch/PVA blend films. The AFM results show that the films' surface became level and smooth due to the cross-linking reaction with the application of formaldehyde. The starch/PVA blend films could biodegrade in the soil environment. The nutrients preliminary solubility and the differential solubility of coated fertilizers is 12.4% and 2.1%,respectively. Cumulative nutrient releaseing of two coated fertilizers can be described quantitatively by the first-degree reaction dynamic equation. The control release rate of starch/PVA coated fertilizer is better than those of cellulose acetate coated fertilizer.