Comparison of Three Spectroscopies for the Determination of Composition of LDPE/PP Blend with Partial Least-Squares
CHEN Ru-huang, JIN Gang*
National Engineering Research Center of Novel Equipment for Polymer Processing, The Key Laboratory of Polymer Processing Engineering of Ministry of Education, South China University of Technology, Guangzhou 510641, China
摘要： 分别利用中红外(mid-infrared, MIR)、近红外(near-infrared, NIR)和拉曼光谱(Raman)采集了31种不同比例的低密度聚乙烯/聚丙烯(LDPE/PP)共混物样本的光谱，利用偏最小二乘法(partial least-square, PLS)建立了光谱数据与LDPE含量的模型，研究了不同光谱范围和预处理方法对模型准确性的影响，并比较了三种光谱定量测量的准确性。结果表明，对于光谱差异小、存在噪音或基线干扰的谱图，预处理方法和光谱范围对模型的准确性均有较大的影响;经过三种预处理以及选择合适的光谱范围建立的模型决定系数(R2)分别从未处理前的0.887 6，0.849 3和0.875 7提升到0.990 6，0.997 3和0.997 2，校正均方根误差(root mean square error of calibration, RMSEC)则分别从10.15，11.75和10.67降低到2.941，1.561和1.598;三种光谱在经过预处理之后均能够较好地定量测量LDPE的含量，NIR和Raman模型准确性更高，由于两者的测量速度快，因此尤其适合于进行快速、准确的定量测量。
关键词：中红外;近红外;拉曼;预处理方法;光谱范围;定量;准确性
Abstract：This paper presented an application of mid-infrared (MIR), near-infrared (NIR) and Raman spectroscopies for collecting the spectra of 31 kinds of low density polyethylene/polyprolene (LDPE/PP) samples with different proportions. The different pre-processing methods (multiplicative scatter correction, mean centering and Savitzky-Golay first derivative) and spectral region were explored to develop partial least-squares (PLS) model for LDPE, their influence on the accuracy of PLS model also being discussed. Three spectroscopies were compared about the accuracy of quantitative measurement. Consequently, the pre-processing methods and spectral region have a great impact on the accuracy of PLS model, especially the spectra with subtle difference, random noise and baseline variation. After being pre-processed and spectral region selected, the calibration model of MIR, NIR and Raman exhibited R2/RMSEC values of 0.990 6/2.941, 0.997 3/1.561 and 0.997 2/1.598 respectively, which corrsponding to 0.887 6/10.15, 0.849 3/11.75 and 0.875 7/10.67 before any treatment. The results also suggested MIR, NIR and Raman are three strong tools to predict the content of LDPE in LDPE/PP blend. However, NIR and Raman showed higher accuracy after being pre-processed and more suitability to fast quantitative characterization due to their high measuring speed.
陈如黄，晋 刚* . 基于偏最小二乘法的三种光谱定量测定LDPE/PP共混物组分含量的比较研究 [J]. 光谱学与光谱分析, 2015, 35(08): 2147-2153.
CHEN Ru-huang, JIN Gang* . Comparison of Three Spectroscopies for the Determination of Composition of LDPE/PP Blend with Partial Least-Squares . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2015, 35(08): 2147-2153.
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