Improved thermal stability of crosslinked PTFE using fluorine gas treatment

Crosslinked PTFE (XF) samples were fluorinated at 293-593 K under 0.7-101 kPa F-2 and for I h to 7 days to improve its thermal stability. Because the weight uptake which may be caused by the fluorine addition was detected at room temperature, C=C bonds in XF can be fluorinated and the fluorine content was saturated after 72 h. Weights of all samples increased more than that of original XF through additional fluorination of C=C bonds, whereas it decreased by the chain-scission to form gaseous fluorocarbons such as CF4. The intensity ratio in IR spectra of the peaks correspond to the double bond (-CF=CF2) at 1785 cm(-1) and the characteristic peaks of PTFE at 1794 cm(-1), I-PTFE/I-PTFE was smaller for the fluorinated XF rather than that for XF. Average values of heat of crystallization (Delta H-c) for all fluorinated XF samples were about 2 J/g higher than that of the original XF. The decomposition temperature calculated from the TG curves increased with increasing reaction temperature and reaction time up to 72 h. Thermal stability of XF was improved through fluorine gas treatment. (c) 2008 Elsevier B.V. All rights reserved.