固相缩聚PET相对分子质量及其分布研究

RELATIVE MOLECULAR MASS AND RELATIVE MOLECULAR MASS DISTRIBUTION OF SOLID-STATE POLYMERIZED PET

建立了 PET固相缩聚反应的数学模型 ,对相对分子质量及粒子内部相对分子质量的梯度分布的模拟与实验结果相符。实验假定粒子内任一微小体积元内聚合物的相对分子质量服从 F lory分布 ,计算产物相对分子质量多分散系数 MWD ,发现粒子内相对分子质量的梯度分布对产物相对分子质量分布的加宽无明显的贡献。认为相对分子质量分布的加宽是由于晶区被排除在反应体系以外造成的 ,且反应条件越苛刻 ,相对分子质量分布越宽。

A mathematical model for solid\|state polycondensation (SSP) of poly(ethylene terephthalate) (PET) was developed. The relative molecular mass at different reaction times and the gradient of average molecular mass along the radius that were predicted by the model were validated with experimental data. In addition, assuming that the normal MWD holds locally for each different depth in a planar particle, the relative molecular mass distribution MWD of the entire particle was calculated. The calculation demonstrated that the MWD increase little during SSP process. The broadening of the molecular weight distribution is attributed to the mechanism that the crystalline fraction was excluded from the reactive system, but not to the gradient of average molecular weight. The stricter the reaction conditions, the wider the relative molecular mass distribution.