Pyrolysis gas chromatography of poly (2, 6-dimethyl-1, 4-phenylene ether)

Abstract

An analytical method for determining the composition of polystyrene-modified poly(2, 6-dimethyl-1, 4-phenylene ether) was investigated by means of curie point pyrolysis gas chromatography.
Using pure polystyrene and poly(2, 6-dimethyl-1, 4-phenylene ether) prepared by the well established method, the dependence of the pyrogram on the pyrolysis temperature and heating period was investigated. Among temperatures studied the optimum one was 590°C considering the simplicity of the pyrogram and the amount of the polymer pyrolysed. The pattern of the pyrogram was a function of the heating period, and then the period was fixed for 4 seconds.
The ratio of the peak area of styrene/2, 6-dimethyl-phenol, (y), on the pyrogram under these conditions, i. e., at 590°C for 4 sec, was plotted against the weight ratio of polystyrene/poly(2, 6-dimethyl-1, 4-phenylene ether), (x), within the range of 30/7070/30. By means of the method of least squares in the regression analysis it was found that the regression line of y on x was y=4.794x+0.150 and that the error variance, V_yx, was 0.084. Linear relationships were also obtained between the ratios of styrene/o-cresol, styrene/2, 4-dimethylphenol, and styrene/2, 4, 6-trimethylphenol peak areas and the weight ratio of polystyrene/poly (2, 6-dimethyl-1, 4-phenylene ether).
In practice it is necessary to investigate the effects of the additives and molecular weight of polymers blended on the pyrolysis pattern. It has been reported in the case of polystyrene with molecular weight higher than 20000 that the yield of styrene on the pyrogram is nearly constant under the same conditions. In this paper two kinds of pure poly (2, 6-dimethyl-1, 4-phenylene ether), i.e., ηinh=0.63 and 1.38 in which range commercial ones have their inherent viscosities, were chosen and blended with the same polystyrene (50/50 weight ratio). Differences in the ratios of the peak area were 5 per cent at most in these two cases. On the other hand, the additives showed differences above 10 per cent. It was found possible to determine the composition of polystyrene-modified poly(2, 6-dimethyl-1, 4-phenylene ether), the effect of the additives being eliminated and a gas chromatograph being operated continuously to minimize the variation from the elaspe of time.