FOURIER-TRANSFORM INFRARED SPECTROMETRIC DETERMINATION OF POLYETHYLENE-GLYCOL IN HIGH-DENSITY POLYETHYLENE

A direct infrared method using Fourier transform infrared spectrometry has been developed for rapidly determining the low relative molecular mass polyethylene glycol (PEG), Carbowax 400, in high relative molecular mass, high-density polyethylene. The PEG analytical band at 1110 cm-1, due to the C-O-C linkage, is first isolated from the overlapping polyethylene bands by spectral subtraction; the integrated absorbance (1000-1170 cm-1) per unit thickness then gives a measure of the PEG concentration in the resin. The method eliminates the tedious and time consuming solvent extraction of PEG from polyethylene. The detection limit is about 0.02% m/m, and the analysis time is 10 min excluding sample preparation which involves melt-pressing the sample into 0.25-0.38 mm plaques. The speed and simplicity of the analysis make the method suitable for quality control laboratories.