Vacuum pyrolysis, PTFE

PTFE decomposes to TFE with first-order kinetics and a 347.4-kJ/mol activation energy under vacuum pyrolysis conditions It is extremely flame resistant and does not bum in air Its limiting oxygen mdex (LOR, the muumum oxygen content of an atmosphere under ambient conditions that sustams combustion, is 96%, which means that it requires almost pure oxygen for combustion... 

In the vacuum pyrolysis of PTFE, the mass spectrum (Fig. 37, bottom trace) appears nearly identical to that of the monomer (Fig. 36, bottom trace) but different from that of the perfluoro-n-alkanes (Fig. 36, top and middle traces). This agrees with the known fact that pyrolysis generates almost the monomer fragments [36]. 

Lewis and Naylor reported the first results on the pyrolysis of PTFE in 1947 [26], At a temperature of 600°C yields of up to 91% TFE were obtained under vacuum (7 x 10 Pa). Under an atmospheric pressure of 1.103 x 10 Pa this yield dropped to only 16%, whereas the yields of HEP and C-C4F8 were increased. 

Evaporating solid polymeric particles (accompanied by considerable pyrolysis) and codepositing the volatile products (mostly radicals) with the metal vapor are used less often. This technique is employed for the formation of 10-mn-diameter copper islets in a polyethylene matrix. The explosive evaporation of a metal wire coated with a polymer and pulsed mechanochemical interactions (of the Bridgeman anvil type), etc. are the modifications of this method. Recently, interest has been shown in the ionic spraying of metals onto polymeric surfaces. Studies of the vacuum deposition of Au and Zn on PE and PTFE should be noted. " ... 

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