PYROLYSIS PRODUCTS OF POLYTETRAFLUOROETHYLENE AND POLYFLUOROETHYLENEPROPYLENE WITH REFERENCE TO INHALATION TOXICITY

Abstract

Analysis of pyrolysis products of polytetrafluorocthylene (PTFE) and polyfluore ethylenepropylene (PFEP) and the influence of pyrolysis conditions on the pyrolysis products were investigated to evaluate the inhalation toxicity of those pyrolysis products. Both polymers were pyrolysed at various temperatures in a flow of nitrogen and air, either dry or humid. The pyrolysis products wcre analysed by infrared spectrometry and combined gas chromatographymass spectrometry. In pyrolysis of both polymers in a nitrogen stream, octofluoroisobutylene was identified in addition to the main products such as tetrafluoroethylene, hexafluoropropylene and octofluorocyclobutane. The main pyrolysis products of both polymers in an air stream were carbonyl fluoride and trifluoroacetyl fluoride. Tetrafluoroethylene and hexafluoropro pylene were far less in quantity but octofluoroisobutylene was found only with PFEP. Perfluoroalkanes were produced by oxidative pyrolysis of PTFE at high temperature. Effect of water vapour in the gas flow on the product formation was significant only in oxidative pyrolysis. In the presence of water vapour, carbonyl fluoride was converted into hydrogen fluoride and carbon dioxide, while trifluoroacetyl fluoride was converted to trifluoroacetic acid and hydrogen fluoride.