Hydrofluoroethylene Polymers in a Vacuum!

Te fl on and tetrafluoroethylene photopolymers, on py rolysis in a vacuum at 423.5 0 to 513.00 C, yield almost J 00 perce nt of monom er. The rate of formation of monomer at a n.,· given tem perat ure fo llows a first-order react ion and is independent of t he method of prepa ration of poly mer or its initial average molecu lar weight. The activation energy was determined by a pressure method and a weigh t met hod, and a value of 80.5 kcal was found b.'· both methods . A prelimina ry heating of Teflo n in air a t 400 0 to 470 0 C did not change appreciably its rate of degradation into monomer when it was subsequently heated in a yacuum . Polyvinyl fluorid e, 1,I -polyv in y li dene fluoride, and polytrifluoroethylene were pyrolyzed in t he range 372 0 to 5000 C. The volatiles consisted in all cases of HF and a wax-like mate rial consist ing of chain fragments of low volatili ty. Polyvinyl fluoride and polyt rifl uoroethylene degrade to complete volatilization, whereas 1,1-poly vinyli dene fluoride becomes stabilized at about 70-pe rcent loss of weig ht. The rate-of-volat ilization curves indi cate a fi l'st-o rder reaction for polyvinyl fluo ri de, a zero-order reaction fo r t riflu oroethy lene, alld an undeterm ined order for 1,1-polyvinylidene fluoride. The orde r of t hermal s tabili ty for t hese poly mers, as com pared with polymethylene, is as follows: Poly vinyl f1uoride < polymeth,vlene < polyt rifluoroethylene< ] . J -polyvi nylidene f1uor idc < polytetrafluoroeth ylene.