High-density polyethylene (HDPE) is a thermoplastic made from petroleum. Deterioration of HDPE materials takes long time due to high molecular mass. In this study, neat HDPE and 5-50% calcium carbonate (CaCO3) reinforced HDPE materials were exposed to different environments for aging. Aging was done in pure water, mineral oil, conventional unleaded gasoline, ammonium hydroxide (NH4OH) and marine conditions. Exposing time of the samples under different liquid medium has been planned for 2, 4 and 6 month periods.