Determination of tacticity in polypropylene by FTIR with multivariate calibration

Author(s)

Ozzetti, Rafael A. ^[1] ; Oliveira Filho, Antonio Pedro de ; Schuchardt, Ulf ; Mandelli, Dalmo

Affiliation

^[1] Universidade de São Paulo (USP). Instituto de Química - Brasil

• Document type: Journal article
• Source: Journal of Applied Polymer Science; v. 85, n. 4, p. 734-745, May 2002.
• Field of knowledge: Physical Sciences and Mathematics - Chemistry

Abstract

A method for determination of tacticity in polypropylene (PP) using FTIR associated with multivariate analysis is presented. Blends of PP with known tacticity were prepared with isotactic, syndiotactic, and atactic polymer and analyzed by 13CNMR. The FTIR spectra were recorded and processed through principal components regression (PCR) and partial least-squares regression (PLS), using information from several different portions of the spectra. The method was compared with the classical methods of tacticity determination by FTIR based on the intensities of the bands at 998 cm-1 (isotactic), 868 cm-1 (syndiotactic), and 975 cm-1 (internal standard), which are known to be dependent on the crystallinity of the polymer and, thus, affected by temperature and sample preparation. The models obtained with multivariate calibration, both with PCR and PLS, gave prediction errors up to fivefold smaller than that of the classical methods, and were also shown not to be heavily dependent on the bands that are affected by the crystallinity of the polymer, but rather on the methyl and methylene bendings at 1375 and 1462 cm-1. (AU)