Characterization of ethylene in EP and in iPP/EP systems by deconvolution of IR spectra

Abstract

ABSTRACT:The purpose of this study is to propose a correlation between IR spectra and molecular structure of ethylene-propylene (EP) copolymers possibly blended with isotactic polypropylene (iPP). The method is based on the deconvolution of the spectrum in the CH 2 -rocking range, i.e., 800 -680 cm Ϫ1, where the bands of interest overlap. The six bands present in this region were signal averaged in position and width. The spectra were then deconvoluted (curve fitted) assuming a Lorentzian shape for the bands. The band at 1167 cm Ϫ1 (with a shoulder at 1156 cm Ϫ1 ) corresponding to a CH 3 vibration is considered as an internal standard. The method was checked by varying some fitting parameters. In order to realize some quantitative measurements, calibration curves were established with some EP samples, characterized by 13 C NMR, which were used as standards. The amounts of total O(CH 2 OCH 2 )O units (ethylene units), isolated ethylene and structural defaults in PP were determined for different iPP/EP blends. Ethylene crystallinity has also been determined. A good correlation was evidenced between infrared and 13 C NMR measurements.

NMR, differential scanning calorimetry, and Fourier transform infrared characterization of the crystalline degree and crystallite dimensions of ethylene runs in isotactic polypropylene/ethylene-propylene copolymer blends (iPP/EP)

“…As described in the preceding paper,7 the ethylene crystallinity can be determined from FTIR spectra using a suitable calibration curve. Results thus obtained are summarized in Table II together with data from DSC experiments.…”

“…The iPP/EP samples were prepared at Solvay by a two‐stage polymerization. Their compositions were determined by 13 C‐NMR in 1,2,4‐trichlorobenzene solution 7. The ethylene content and triad distribution were calculated according to Ray et al8 The n 2+ parameter is defined as the number‐average sequence length for methylene sequences containing two carbons at least.…”

“…The ethylene content and triad distribution were calculated according to Ray et al8 The n 2+ parameter is defined as the number‐average sequence length for methylene sequences containing two carbons at least. It was derived7 according to Randall 9…”

“…A full characterization of the same series of samples, including ethylene content and ethylene distribution, has been performed using deconvolution of IR spectra. The results were reported, and compared with those from a parallel solution 13 C‐NMR characterization, in a previous paper 7…”

NMR, differential scanning calorimetry, and Fourier transform infrared characterization of the crystalline degree and crystallite dimensions of ethylene runs in isotactic polypropylene/ethylene–propylene copolymer blends (iPP/EP)

“…7 The ethylene content and triad distribution were calculated according to Ray et al 8 The n 2ϩ parameter is defined as the numberaverage sequence length for methylene sequences containing two carbons at least. Their compositions were determined by 13 C-NMR in 1,2,4-trichlorobenzene solution.…”