Determination of total short-chain branching in polyethylenes by computerized data processing of infrared spectra



A computer method is described to determine the short-chain branching of polyethylene from IR spectroscopic data. The shape of the band at 1378 cm−1 (characteristic to the methyl side groups) was calculated by using first a deconvolution procedure (Ishige method) for the envelope curve of the overlapping peaks in the region of 1300-1400 cm−1, followed by a convolution calculus applied only to the deconvoluted points of the peak in question. The results were in good agreement with values determined by Willbourn's compensation method.