was found from the following equation using a contact angle measuring machine ca d made by kyowa interface science co ltd in the equation h height of a spherical water drop and r radius of a spherical water drop heat of crystal fusion was measured using a differential thermal analyzer dsc 7 made by perkin elmer inc under a nitrogen current of 60 cm 3 minute at a temperature increase rate of 20 u00b0 c minute the higher the melting heat is the higher the crystallization degree of ptfe diffuse reflectance was measured according to astm e308 wavelength 400 to 700 nm using mini scan xe plus made by the color management company pressure loss was measured using model 8130 made by tsi co ltd in an air flow rate of 35 9 l minute at a differential pressure of 150 mmh 2 o a porous ptfe membrane was set in filter holder model 8130 made by tsi co ltd the air flow rate of the exit side was adjusted to 35 9 l min by adjusting the pressure and air containing colloid particles having a particle size of 0 3 u03bcm was filtered after measuring the number of permeated particles with a particle counter the collection efficiency was calculated from the following equation collection efficiency 1 concentration of permeated particles in downstream area concentration of particles in air of upstream area u00d7 100 a paste mixture containing 80 parts of ptfe fine powder prepared by emulsion polymerization and 20 parts of naphtha was extruded using an extruder at a reduction ratio of 80 1 to obtain a rod shaped extruded article having a diameter of 18 mm the rod shaped extruded article was rolled in the extrusion direction using a calender roll having a diameter.