A separator was composed of the particle mixtures wish polymer(UHMWPE, HDPE), process oil(mineral oil), silica carbon black and BHT. Two kinds of separators extracted process oil, and process oil and silica with PR(polymer g/process oil g) were prepared, and then their properties were investigated. The specimen which was extracted by nonpolyar organic solvents extracted process oil of nearly 98%. The extracted amount of silica showed slowly the weight loss of specimens with the lapse of 30 min in sodium hydroxide solution. The resistance of specimens against sulfuric acid showed the weight loss of specimens of nearly less than 1 % with the increase of PR(polymer g/process oil g) ratio. As the PR ratio was increased, the tensile strength was increased but the electrical resistance of specimens showed the high resistance value. The isotherm by N₂ gas adsorption-desorption method exposed the increase of the surface area with the increment of process oil having hysteresis regions of capillary condensation. In the result of SEM analysis, the micropores within PE layers was well distributed as the amount of process oil was increased.