Release Kinetics of Urea from Polymer Coated Urea and Its Relationship with Coating Penetrability

• 作 者: ZHANG Hai-jun WU Zhi-Jie CHEN
• 机 构: Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China
• 出 处: 城市道桥与防洪
• 发表日期: 2004年期
• 关键词: Polymer coated urea Urea release kinetics Coating penetrability Fitting

Four kinds of polymer coated urea (PCU) were put in distilled water at 30C to determine the variation of coating penetrability and give a precise description of the urea release kinetics. The urea release from PCU could be divided into four stages: lag stage, swell stage, steady stage and decay stage. The release rate coefficient K, a measure of coating penetrability, was linearly increased at swell stage, but almost not variable at steady stage. At decay stage, the relation of K to time t could be described by the equation K＝ mtn-1(where m and n are the coefficients). When n＞1, the coating penetrability was gradually increased, and the urea release from PCU was accelerated; when n＝1, the coating penetrability was steady, and the urea release from PCU obeyed the first-order kinetics; and when n＜1, the coating penetrability was gradually decreased,and the urea release from PCU was delayed, resulting in a significant "tailing effect".