纯溶剂在线性低密度聚乙烯膜中扩散的计算

为了评价和预测密封材料线性低密度聚乙烯(LLDPE)的防渗透性能,结合实验和数学模型2种手段,研究5种化工溶剂在LLDPE薄膜中的扩散性能.采用稳态渗透汽化实验和吸附溶胀实验分别获得各组分的渗透通量数据和平衡吸附量.引入Fujita自由体积模型阐述扩散系数,根据渗透通量实验数据拟合得到各组分的自由体积参数.结果表明,渗透通量的计算值与实验值基本一致.根据模型计算得到5种溶剂的扩散系数随温度变化的曲线.通过求解Fick第二定律的偏微分方程数值解,得到不同时刻5种溶剂在平板膜内部的质量浓度分布曲线.结果表明,LLDPE对5种溶剂的防渗透性能良好.

Calculation of diffusion behavior of pure solvents through linear low-density polyethylene(LLDPE) membrane

The diffusion behaviors of five kinds of pure solvents through LLDPE membrane were investigated by experimental and numerical methods in order to evaluate and predeterminate the anti-infiltration performances of linear low-density polyethylene(LLDPE) sealing material.The permeation flux and equilibrium absorption capacity in the LLDPE membrane were obtained from steady pervaporation experiments and swelling experiments respectively.The diffusion coefficient was described by Fujita free volume theory and the parameters in the model were obtained by fitting a numerical solution of the flux equation to experimental data.The calculated fluxes using the free volume model accorded well with experimental results.The calculated diffusion coefficients for five kinds of solvents in LLDPE at different temperatures were drawn based on the mathematical model.Mass concentration distribution curves for five kinds of solvents in the plate membrane were calculated by numerically solving the partial different equation of Fick’s second law.Results showed that LLDPE material had excellent anti-infiltration performances for five solvents.