Morphological characteristics of carbon/polytetrafluoroethylene films deposited on porous carbon support

The effect of polytetrafluoroethylene (PTFE) content on morphological characteristics of carbon/PTFE films deposited on porous carbon support was investigated by mercury-porosimetry, scanning electron microscopy (SEM) and a.c. impedance spectroscopy. The microstructure of the film was affected by the content of fluoropolymer. The layer has two distinctive pore distributions with a boundary of about 0.35 mu m. The polymer coated the pores with size higher than 1 mu m (carbon interagglomerate pores), while the pores with size lower than 1 mu m were not influenced by the presence of PTFE. Above 40 wt% PTFE, a further supply of polymer did not fill the pores, but increased the thickness of the sample. The presence of cracks, increasing in number and size with PTFE content, was also revealed. (C) 1998 Chapman & Hall.