利用拉曼光谱检测乙丙共聚物中乙烯含量

通过分析不同乙烯含量的聚丙烯样品的拉曼光谱,并结合偏最小二乘法(PIS),对聚丙烯中的乙烯含量进行了研究.对比聚乙烯和聚丙烯的拉曼光谱,分析了 50～600,600～1 600及2 700～3 100 cm-1 等三个特征谱段的拉曼光谱谱图;建立了乙烯含量的 PLSI 回归模型,发现利用 50～3 600 cm-1 全谱段拉曼光谱建立的乙烯含量模型的预测效果最佳,与近红外光游(NIR)的检测值结果相近,与真实值间的线性相关系数(r)、平均相对误差(RAI))和均方根误差(RMSE)分别为0.995,2.65%和0.319.对50～3 600 cm1 范围的拉曼光谱进行 PLS 分析,发现第一项 PLS 成分的载荷分布能够反映乙烯含量与聚丙烯分子结构间的关系,即与 CH2 的数量成正相关,而与CH3,C-H 和 C-C 键的数量成负相关.研究表明,利用拉曼光谱可实现乙丙共聚聚丙烯中乙烯含量的快速检测.

Measurement of ethylene content in polypropylene by Raman spectrum

Ethylene content in polypropylene was studied by Raman spectrum, combined with partial least squares (PLS) method. The comparison between Raman spectra for polyethylene and polypropylene was carried out, and the spectra between 50 and 600, 600 and 1600, and 2700 and 3100 cm(-1) were analyzed respectively. The models for ethylene content prediction were built, while the model based on 50-3600 cm(-1) spectra gave the best performance. The experiment indicated that Raman spectrum gave the similar predictive results as the near infrared (NIR) spectrum; the values of correlation coefficient (r), relative average deviation (RAD) and root mean square error (RMSE) between predictive results and actual values were 0.995, 2.65% and 0.319, respectively. According to PLS analysis, the loadings of factor 1 could reflect the relationship between the composition of polypropylene molecular chain and ethylene content, and ethylene content had a positive correlation with CH2 content, but a negative correlation with content of CH3, C-H, and C-C. The results indicated that it was feasible to detect the ethylene content in polypropylene by Raman spectrum.