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Lots of ions were observed in the spectra of polyethylene heated in the ion source of a mass spectrometer for the temperature range of 150-330°C. With elevation of temperature, the rate of ionic yield displayed a stage of slower increase(Process I), followed by a steeper uprise(Process II). For two brands of commercial polyethylene, Marlex and Hostalen, it was found that the values of activation energy for the latter stage appeared to be 34.0kcal/mol for Marlex and 24. 7kcal/mol for Hostalen. On the other side, the values for Process I were found to be 6. 5± 1.2kcal/mol for both samples. According to the mass spectra and the values of activation energy, it was concluded that Process II is corresponding to the stage of thermal degradation, which is presumed to be caused by some of the weak-links in the polymer molecule, while Process I would be explained by the presence of a stage of evaporation of lighter components contained originally in polyethylene. Thus the possibility of analyzing the structure of high polymers is suggested by regarding these volatile components as a miniature model of polymers.

shitsuryou bunseki/shitsuryo bunseki

Mass Spectrometric Study on the Structures and the Degradation Reactions of High Polymers. I. Preliminary Investigation on the Volatile Components in Commercial Polyethylene by Utilizing the Ion Source for Gas Alnaysis