采用分子动力学（MD）模拟方法研究了O2、CO2小分子在不同质量比（90／10、70／30、50／50、30／70和10／90）聚对苯二甲酸乙二醇酯（PET）／聚乳酸（PLA）共混物中的扩散行为，基于Einstein关系式计算了小分子在共混物中的扩散系数。讨论了不同探针半径对自由体积分数（FFV）的影响以及自由体积分数与扩散系数的关系。研究结果表明，探针半径越大，自由体积分数越小；扩散分子的动力学半径越小，在同一比例PET／PLA共混物中的扩散系数越大，与自由体积理论取得统一。当PET／PLA共混物质量比为70／30时共混物的阻隔性能最好。
Diffusion of oxygen and carbon dioxide molecules in polyethylene terephthalate(PET)/polylactic acid (PLA)blends(with mass ratio of 90/10, 70/30, 50/50, 30/70 and 10/90) were investigated by molecular dynamics simulations. The diffusion coefficients were calculated based on Einstein relation. The influence of different probe radii on the fractional free volume, and the relationship between fractional free volume and diffusion coefficients were discussed. The results show that the larger the probe radii is, the smaller the fractional free volume becomes. With the same mass ratio of PET/PLA blend, the smaller the kinetic radius of diffusion molecular is, the larger the diffusion coefficients is, which integrates with the free volume theory. The barrier properties of PET/PLA blend is to be the best when the mass ratio is 70/30.
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