聚合物包膜尿素溶出动力学特征及其与包膜层通透性的关系

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

通过聚合物包膜尿素(PCU)在30℃纯水中的溶出试验,精确描述了PCU尿素溶出的动力学特征。将PCU尿素溶出过程分成4个阶段:滞后阶段、溶胀阶段、稳定阶段和衰退阶段。同时,基于Fick扩散第一定律,确立了PCU尿素溶出速率与包膜层通透性的关系方程,并根据此方程,推断出PCU尿素溶出过程中包膜层通透性的变化情况。结果表明,在溶胀阶段,溶出速率系数K(包膜层通透性的量度)逐渐变大;在稳定阶段,K为一稳定值;在衰退阶段,K随时间t变化可以用公式K=mt^(n-1)表示(式中m和n均为常数)。当n>1时,包膜层的通透性逐渐增大,肥心尿素溶出加快;当n=1时,包膜层通透性稳定,肥心尿素以一级动力学方式溶出;当n<1时,包膜层通透性逐渐减小,肥心尿素溶出变慢,导致明显的“尾留效应”。

The release experiment of polymer coated urea (PCU) was carried out in pure water at 30C to give a precise description of the release kinetics of urea from PCU. The processes of urea release from PCU could be divided into four stages: lag stage, swell stage, steady stage and decay stage. Meanwhile, the relationship between urea release rate from PCU and the penetrability of its coating layer was obtained based on the first Fick' s diffusion law. According to the relationship, variation of coating layer's penetrability with urea release from PCU was evaluated. The results showed that, at swell stage, the release rate coefficient K, a measure of coating layer' s penetrability, gradually increased; at steady stage, K value was almost not variable; at decay stage, the response of K to time ?could be described by the e-quation K = mtn-1(where m and n are constants), when n > 1, the penetrability of coating layer was gradually increased , and urea release from PCU was accelerated; When n = 1, the penetrability of coating layer was steady, and urea release from PCU coincided first-order kinetics; when n < 1, the penetrability of coating layer was gradually decreased, and urea release from PCU was delayed, which would result in a significant 'tailing effect .