EXPRESS: Prediction of the Molecular Weight of Polyethylene Using Raman Spectroscopy with Multivariate Data Analysis

In this study, a simple procedure to estimate the molecular weight of high-density polyethylene over a very wide range of molecular weights was investigated using Raman spectroscopy with multivariate data analysis. High-density polyethylene samples with viscosity average molecular weights (Mv) [g/mol] ranging from 0.1 to 7.4 million were synthesized, and their Raman spectra in the 3200 to 100 cm^-1 region were measured. Using multivariate analysis to develop a calibration model derived from each spectrum and molecular weight, a high correlation coefficient was achieved between the predicted and actual values of the model. Thus, this study shows that Raman spectroscopic method can be employed for estimating the molecular weight of high-density polyethylene. Furthermore, Raman spectroscopy can be implemented in optical systems utilizing optical fibers, enabling operation with the measurement point separated from the main device even in harsh process environments, including high temperatures. Consequently, this technique is highly resistant to environmental conditions and is extremely useful as a measurement method applicable in any measurement environment. In practical applications, the spectroscopic technique will be selected according to the purpose and measurement environment, aiming for industrial application of this method.