Fabrication of a porous structure of poly(tetrafluoroethylene) from a mixture with fumaric acid

Porous rods of poly(tetrafluoroethylene) (PTFE) were fabricated by molding PTFE powder and fumaric acid (FA) at room temperature and sintering at 400 °C. The microstructures of the molding mixtures were observed with a scanning electron microscope (SEM). Although rectangular crystals of FA immersed in the fibrous structure of PTFE were observed in the extrudates of PTFE before sintering, open holes were created by the sublimation of FA dispersed in PTFE after heating the extrudates at 310 °C; the open holes remained even after sintering at 400 °C. High-resolution images from SEM revealed that the fibrous structure heated at 310 °C was composed of small particles of PTFE connected with fibrils, and these particles were sintered into grains after heating at 400 °C. Pore size could be controlled by changing the volume fraction of FA. The dimensions of extrudates were measured to determine porosity and volume shrinkage. The mechanism for the formation of the porous structure is discussed on the basis of SEM images, porosity and volume shrinkage. Porous rods of poly(tetrafluoroethylene) (PTFE) were fabricated by molding PTFE powder and fumaric acid (FA) at room temperature, and sintering at 400 °C. The microstructures of the molding mixtures were observed with a scanning electron microscope (SEM). High-resolution images of SEM revealed that the fibrous structure heated at 310 °C is composed of small particles of PTFE connected with fibrils, and these particles were sintered into grains after heating at 400 °C. Pore size could be controlled by changing the volume fraction of FA.