Coating of urea fertilizer with cardanol

Abstract

Controlled release urea coated with cardanol was investigated. Film properties such as drying time, hardness, adhesion, glossiness, water resistant and acid/base resistant of various cardanol based films for example, film prepared from prepolymerization cardanol, prepolymerization cardanol blended with drying oils such as tung oil, linseed oil and cardanol-formadehyde resin were compared. Then the shortest drying time for coating was selected. It was found that a mixture of prepolymerization cardanol and tung oil at ratio 9:1 (w/w) at 80 celcius gave the shortest drying time and it was selected as a coating material. The most suitable amount of coating material was 6 % by weight of fertilizer. Cobalt naphthenate and tertiary butylhydroperoxide at 6 % (w/w) of coating material were used as catalyst. The coated urea had hard coating film, glossy and did not dissolve in water. When the nutrient release was investigated, it was found that coated urea gave lower release rate than uncoated urea. Moreover, the thicker coated film gave slower release rate. The high temperature accelerated urea release while alkaline condition retarded release rate. In addition, it was found that urea release from fertilizer coated with a mixture of prepolymerization cardanol and tung oil at approximate 125 micron thickness could be prolonged to three months.