Study On The Extrusion Of PLA/PBL With In-line Near Infrared Spectroscopy

Blending is one of important polymer modification methods. Compositions and their dispersions of blend are two critical parameters, which have great influence on the performance of materials and quality of products. However, those two parameters are not easy to monitor in real-time during the process of blending due to the lack of an in-line monitoring technique and corresponding equipment. For this reason, a solution, appling in-line near infrared spectroscopy(NIR) monitoring technique and developing an in-line NIR monitoring system, was proposed to monitor the process of polymer processing combined with chemometrics.In this study, the self-developed in-line NIR monitoring system was introduced, of which the main hardware of the system, namely sensor, was tested in terms of performance and reliability. Then, this system was used to in-line measure the poly(lactic acid)(PLA) compositions of a series of extruding poly(lactic acid)/poly(butylene adipate-co-terephthalate)(PBAT) with varied proportions. The spectra collected were firstly qualitatively analysed with principal component analysis(PCA) and then imported to develop principal component regression(PCR) quantitative models and partial least squares(PLS) quantitative model. The optimal PLS calibration model for PBAT composition was achieved after comparsion, which exhibited coefficient of determination(R2)/root mean square error of calibration(RMSEC) value of 0.9989/1.053 Wt. % with validation results of R2/root mean square error of prediction(RMSEP) valued of 0.9954/2.059 Wt. %. Those results showed comparative accuracy and potential of prediction with the reuslts based on the off-line spectra of extruded PLA/PBAT blends. Finally, using this optimal PLS model for PBAT composition based on in-line spectra, PBAT dispersions of extruding PLA/PBAT with a proportion of 50:50 at different processing temperatures were measured, of which results were in agreement with results characterzised by scanning electron microscope(SEM). All above suggested that the developed in-lin NIR monitoring system was able to accurately measure the PBAT composition as well as dispersion during the process of extursion of PLA/PBAT combined with chemometrics.