Study On In-line Measurement And Characterization Methods Of Binary Polymer Blend During Extrusion Using Raman Spectroscopy

The component content and content uniformity of polymer blends are two critical parameters,which have an important effect on the performance of products.At present,the two physical parameters are measured by off-line methods,such as chromatograph and electron microscope.However,off-line methods which are hysteresis,destructive,and unrepresentative for the whole sample.Therefore,in this article,Raman spectroscopy as an in-line measurement technology is applied for real-time detection and characterization of the component content and content uniformity during polymer blending and modification,which is helpful to deeply understand the process of polymer blending and modification,promote application of Raman spectroscopy as an in-line measurement technology in the field of polymer processing,and has a scientific and practical significance.In this article,at first,the self-developed in-line measurement system of Raman spectroscopy was constructed,and the main hardware and software of the system were checked in the aspects of perfoemance and reliability.Then,the system was applied to in-line measurement of the polystyrene(PS)content of a series of extruding polypropylene(PP)/PS with varied proportions.And different pretreatment and multivariate calibration methods were used to develop the optimal PLS model of PS which was compared with the optimal PLS model of PS based on off-line infrared spectroscopy.What’s more,the self-developed in-line measurement system of Raman spectroscopy was successfully applied to measure PS content variation from 80 Wt.% to 50 Wt.% then to 20 Wt.%.Finally,by means of the optimal PLS model of PS based on in-line Raman spectroscopy,the content uniformity of PS in extruding PP/PS with a proportion of 70:30 at different screw speed were obtained and compared with the content uniformity of PS acquired by off-line scanning electron microscope(SEM).Research results showed that compared with PS content acquired by off-line infrared spectroscopy,PS content acquired by in-line Raman spectroscopy showed comparative accuracy and potential,which was achieved exhibiting calibration results that coefficient of determination(R2)/root mean square error of cross validation(RMSECV)turned out 0.9998/0.438 Wt.%,and prediction results that R2/root mean square error of prediction(RMSEP)turned out 0.9993/0.725 Wt.%.The coefficient of variation of PS content at 30 rpm,60 rpm,90 rpm,120 rpm,and 150 rpm was respectively 10.95 %,7.24 %,6.43 %,5.54 %,and 5.03 %,which was in agreement with the coefficient of variation of PS content characterized by SEM.All of the above suggested that the self-developed in-line measurement system of Raman spectroscopy was able to accurately measure the component content and content uniformity of PS during blending and modification of PP/PS.