Composition estimation, using Fourier transforms

Principal Component Regression (PCR) was used by Tuchbreiter and MueUiaupt to determine the composition of a number of random ethane/propene, ethane/1-hexene, and ethane/l-octene copolymers [120]. After polymerization, the polymers were characterized by both Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FT-IR) and C NMR and multivariate calibration models using PCR were subsequently developed to estimate the co-monomer content. 

Because the IV is a measure of the relative unsaturation of a compound or sample, other analytical techniques (e.g., gas chromatography of FA composition, AOCS Cd lc-85) can be used to estimate the value. Interest in recent years has focused on spectroscopic techniques for the rapid determination of TV. Fourier transform (FT)-near-infrared, near-infrared, FT-Raman, and H and nuclear magnetic resonance (NMR) spectroscopic techniques have all been investigated (Ng and Gee, 2001). The most promising results have been obtained with FT-near-infrared spectroscopy, which only takes a few minutes to determine the iodine value (Cox et al., 2000). 

The composition of PVDF samples in terms of its different crystallite phases can be investigated by means of XRD (the p-phase exhibits a peak in the XRD pattern at 26 = 20.5°), and of Fourier-transform infrared (FTIR) spectroscopy (for instance, the P-phase shows strong vibration peaks at about 840 cm and 1280 cm ). To give an idea, in order to estimate the fraction, tpp, of the P-phase from FTIR measurements, the following formula is often used, which comes from assuming Beer-Lambert absorption, and related absorption coefficients that are known for both the a- and the P-phases ... 

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