Effect of the High-Pressure Hydrogen Gas Exposure in the Silica-Filled EPDM Sealing Composites with Different Silica Content oleh Hyun Min Kang, Myung Chan Choi, Jin Hyok Lee, Yu Mi Yun, Jin Sub Jang, Nak Kwan Chung, Sang Koo Jeon, Jae Kap Jung, Ji Hun Lee, Jin Hong Lee, Young Wook Chang, Jong Woo Bae