关键词:

无限稀释扩散系数, 小分子溶剂, 聚乙烯粒子, 反相气相色谱

Abstract:

Based on the classical theory of linear and non-equilibrium chromatography process, the infinite dilution diffusion coefficients of dichloromethane, tri-chloromethane, tetra-chloromethane and n-hexane in nascent polyethylene particles were measured in the temperature range from 323.15 K to 358.15 K with inverse gas chromatography (IGC). Polyethylene particles, as obtained from the polymerization reactor, were directly used to prepare packed columns without any change of the polymer morphology. The effects of diffusion temperature, molecular weight of different solvents and polyethylene crystallinity on diffusivity were investigated. It was shown by the IGC results that the diffusion coefficients increased with rising temperature for a particular polymer/solvent system, while decreased with increasing molecular weight of diffusing solvent for homologue solvents, such as dichloromethane, tri-chloromethane and tetra-chloromethane. The crystallinity of semicrystalline polyethylene also affected the diffusion coefficients significantly in the way that higher crystallinity corresponded to lower diffusion coefficients for both dichloromethane and n-hexane. The measured diffusion coefficients were compared with model predicted values and good agreement was found, indicating the reported IGC method in this work had good reliability.

Key words:

无限稀释扩散系数, 小分子溶剂, 聚乙烯粒子, 反相气相色谱