Preparation and Characterization of Triple Polymer-Coated Controlled-Release Urea With Water-Retention Property and Enhanced Durability

Triple polymer coated with controlled-release water retention fertilizer (TCWF) and enhanced mechanical property was developed by coating polyethylene (first layer), poly (acrylic acid-co-acrylamide) superabsorbent (second layer), and poly (butyl methacrylate) (third layer) consecutively on the granule core urea in the fluidized-bed coater. The inner layer possessed controlled-release property, the middle layer had water absorbent characteristic, and the thin outer layer aimed to protect the fragile layer of the superabsorbent. The relationship between the thickness of coating layer and the nutrient releasing properties was established. The effects of polymerization parameters on the water absorbency of the superabsorbent were studied and optimized as well. The nutrients release behaviors of this triple-coated urea in both water and soil were investigated and compared. The results showed that TCWF not only performed as a good controlled-release fertilizer but also had excellent water retention capacity. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 2103-2111, 2011