ESTIMATION OF CRYSTALLINITY IN POLYETHYLENE BY RAMAN-SPECTROSCOPY

The quantitative determination of crystallinities of polyethylene samples from the analysis of vibrational bands due to delta(CH2) twisting and nu(CC) stretching in the Raman spectra between 950 and 1500 cm-1 was assessed. Several methods based on manual resolution of band envelopes and on computer-derived information using Gaussian and Lorentzian profiles were compared. The major source of error was found to be the estimation of the amorphous and crystalline interphase content, alpha(b). A new method for the determination of sample crystallinity is proposed based on the time-dependent Fourier transform deconvolution of the spectral region between 950 and 1500 cm-1, which takes into account the baseline corrections and the influence of vibrational band shoulders in this region to obtain consistent values of alpha(a), alpha(b) and alpha(c).