Pyrolysis of polyisobutene (Vistanex), polyisoprene, polybutadiene, GR-S, and polyethylene in a high vacuum

Abstract

amples of polyisobutene, polisoprene, polybutadiene, GR-S, and polyethylene, weighing about 25 to 50 milligrams, wcre pyrolyzed in a vacuum of about 10-6 millimeter of mercury in a specially designed apparatus at temperatures ranging between 300 0 to 475 0 C. The volatile products of pyrolysis were separated into four fractions: (IV) gaseous, volatile at -196 0 C; (IlIA) liquid, at -75 0 C; (IlIB) liquid, at 25 0 C and (II) wax-like fraction , volatile at the temperature of pyrolysis. The gaseous fraction was analyzed in the mass spectrometer and was found to consist in all cast'ls of CH4 The liquid fraction, I lIA, was analyzed similarly and was found to give a mass spectrum characteristic for any given polymcr. A molecular weight determination of the wax-like fraction by the microfreezing-point-lowering method, showed it to vary from 543 to 739, dtlpending on the polymer from which the fraction was obtained. It is shown that the method of pyrolytic fractionation of high molecular weight polymers, in conjunction with mass spectrometer analysis of the more volatile fractions, can serve as a means of identifying the polymers.