Current manual sampling and analysis methods

such as refractive index measurement

chromatography

etc.

have complex operations

time lags and human errors.Therefore

they cannot be used to evaluate the esterification process in polyester production in real time and determine the clear point of the reaction.In this article

an online Raman analysis system with 1 064 nm as the laser wavelength was set up to collect continuously the spectra of the esterification reaction between terephthalic acid(PTA) and 1

3-propanediol(PDO) to create poly(tri methylene terephthalate)(PTT)

while using Savitzky-Golay algorithm to make baseline correction on the collected spectra.The principal component analysis was used to extract the spectral information.Based on the principle of esterification process

a qualitative analysis method was established to determine the clear point by using the area ratio for Raman characteristic peaks of benzene loop located near 1 604 cm-1 and ester group located at 1 720 cm-1.Results showed that the developed Raman spectroscopy could accurately reflect the clear point in the esterification process of polyester prodction

With the advantages of good real time performance

simple operation and rapid analysis

it provides a reference for the process control and product quality control of polyester production.