A New Calibration Method for the Accurate Determination of Ethylene Content in Ethylene-Propylene Copolymers by CRYSTEX-IR

Polyolefin Characterization – ICPC 2010. Macromolecular Symposia.
Volume 312, 2012, Pages 157-166.
L. Romero, A. Ortín, J. R. Torres Lapasió, M. C. García Álvarez Coque.
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CRYSTEX is a fully automated instrument for the determination of Xylene Solubles in polypropylene and ethylene-propylene copolymers, providing an excellent correlation with gravimetric methods. The instrument can be equipped with a dual-band infrared (IR) detector to quantify the ethylene weight percentage (C2%) in the amorphous fraction, and in the whole polymer sample. In this work, a new approach based on multiple linear regression (MLR) models is presented, which makes use of two independent IR absorbance signals acquired simultaneously by the detector.

A compromise model to predict directly C2% is proposed, which balances good accuracy and reduced experimental effort. MLR models able to predict the total sample concentration were also developed. The results were successfully validated using copolymer standards in a wide chemical composition range.


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