THERMAL AND CATALYTIC BEHAVIOR OF GRAFTED POLYTETRAFLUOROETHYLENE (PTFE) PRETREATED WITH SOME TRANSITION-METAL NITRATES

A hydrophobic PTFE solid material has been grafted with acrylic acid ( AAc) via exposure to a dose of 20 kGy gamma radiation. The obtained hy drophilic solid (PTFE-g-PAAc) was impregnated with a solution containi ng a known amount of nitrate of cobalt, copper, ferric or nickel. The extent of loading of metal species was fixed at 16 wt.-%, expressed as metal oxide. DTA, XRD, LR and catalysis of CO-oxidation reaction with oxygen have been carried out on the various prepared solids. The resu lts obtained revealed that PTFE melts at 355 degrees C, PAAc in the gr afted PTFE melts at 230 degrees C. The presence of cobalt or copper sp ecies considerably modified these temperatures; as a result of their c omplete participation in metal-polymer complexes formation. This effec t was much less pronounced in the case of nickel and iron cations. Ver y strong exothermic peaks were detected in the DTA curves at 260-290 d egrees C for Fe, Co, Cu species and at 340 degrees C for Ni species. T hese strong peaks characterize the thermal decomposition of the metal polymer complex with subsequent formation of free amorphous metal oxid e. The catalytic activities measured at 200 degrees C for different so lids heated in vacuum at 240 degrees C have been found to vary in the following sequence: Co > Cu much greater than Fe > Ni. These results w ere attributed to the extent of different transition metal cations inv olved in the metal-polymer complex formation, their thermal stability, and the specific activity of the produced corresponding metal oxides.