Determination of acid end group in Polybutylene Terepthalate using Fourier Transform near-infrared (FT-NIR) spectroscopy and chemometrics

A robust quantitative method for the determination of acid end group (AEG) in Polybutylene Terepthalate (PBT) pellets using near-infrared (NIR) diffuse reflectance spectroscopy and chemometrics is presented in this paper. A set of 66 calibration samples were used to develop a multivariate calibration model based on partial least-squares (PLS) regression. The AEG in the calibration samples varied from normalized concentration of 20-90 meq/kg. To minimize non-chemical spectral variations, the acquired NIR spectra were preprocessed using standard normal variate (SNV). Spectral range selection was explored in order to identify optimal spectral regions that were required to generate a robust PLS regression model for AEG. The performance of the optimized PLS model was evaluated on a set of 219 independent validation samples. The optimized calibration models exhibited RMSEP of 2.87 meq/kg.