Scission Products and Molecular Weight Effects on the Combustion of Polyethylene
Erika NAKASHIMA, Tomonaga UENO, Masao YUKUMOTO and Kunihiko TAKEDA
Abstract:The mutual relations between the flame positions during the vertical combustion test and the thermal degradation of polyethylene (PE), polypropylene (PP) and polybutene (PB) as polyolefin and polystyrene (PS) were studied. The flame developed downward for PE and upward for PS. The flames of PP and PB remained in the middle. The combustion of polymer materials has been thought to occur on the surface of the material after having been ignited. However, from the result of the vertical combustion test, it was understood that a flame exists on the surface of the material that drips from PE. The vaporization of the sample is not thought to occur in the primary degradation, but in the secondary degradation phase, when it reacts with oxygen. In order to analyze the phenomena, the scission products of those polymers were measured by Py-GC-MS. When the combustibility of PE of different molecular weight was evaluated by the vertical combustion test, PE of lower molecular weight did not burn where as PE of higher molecular weight did. PE of the lower molecular weight only melted without ignition. Even if the Bunsen flame of the burner was applied to the thinly dripping melted material, it would not ignite. It was then concluded that PE with lower molecular weight does not degrade and vaporize in the secondary degradation. Key Words:Polyethylene, Combustion, Degradation, Molecular weight, Mass spectrometer