In-line sensing of CO{sub}2 concentration in polymeric extrusion foaming process

摘要

An in4ine sensor using near infrared (NIR) spectroscopy was developed for sensing carbon dioxide (CO{sub}2) concentration in molten polymers during the extrusion foaming process. The sensor obtains the CO{sub}2 concentration from the measured NIR absorption spectra. The spectra were acquired in-line through probes equipped at the die of the extruder. The experiments were conducted on three different polymers, polypropylene (PP), low-density polyethylene (LDPE) and polybutylene succinate (PBS), at different flow rates and at different operating temperature. By employing wavelet transforms for analyzing the NIR spectra, the influence of the operating conditions such as operating temperature and flow rate on CO{sub}2 measurement could be eliminated. The regression model derived from the wavelet-treated NIR spectra could successfully estimate the CO{sub}2 concentrations for all three polymers.