The pyrolysis and nonflaming oxidative degradation of poly(vinylfluoride)

Abstract

AbstractThe thermal degradation of poly(vinylfluoride) (PVF) was studied under slow heating conditions to 1000°C with and without the presence of air. The degradation products, classified as low‐boiling volatiles, high‐boiling volatiles, and nonvolatile residues, were analyzed quantitatively by gas chromatography—mass spectrometry and several spectroscopic methods. Initial stages of degradation begin at 420°C with the evolution of HF and benzene and rapidly reach a maximum in sample weight loss by 450°C. One‐third of this weight loss was in the form of hydrofluoric acid (HF) and at least 70 low‐boiling volatile compounds that consisted of substituted aromatics, unsaturated hydrocarbons, and multiple‐ring compounds, many of which contained a fluorine atom. The high‐boiling volatile fraction contained compounds with more aliphatic but less aromatic character than the low‐boiling. The nonvolatile residue retained 4% of the original fluorine content and exhibited strong unsaturated character. In the presence of oxygen HF, CO, and H2O were the major constituents of the low‐boiling volatiles; the organic fraction was essentially unchanged in composition but reduced in overall concentration. The overall weight‐loss process was bimodal in air and produced a thermally resistant residue that degraded by 650°C. A comparison of degradation products from poly(vinylchloride) with this work demonstrates that PVF forms more lower‐molecular‐weight, halogen‐containing compounds, whereas the former produced more HCl and nonvolatile residue containing a lower halogen content.