This book studies the mechanical properties (hardness and wear)and physical properties (thermal conductivity and water absorption) for HDPE/Al2O3, HDPE/TiO2 composites and HDPE/l2O3/ TiO2 hybrid composites with different weight percentages of fillers prepared by hot pressing method.Hardness test results had shown that hardness increase with increasing the weight percentages of fillers and the results showed that the hardness of hybrid composites HDPE/Al2O3/TiO2 were higher than HDPE/Al2O3 and HDPE/TiO2 composites.Wear results showed that the wear rate of composites decrease with the increasing the weight percentages of fillers, hybrid composites have less wear rate compared to other composites. The thermal conductivity results showed that the thermal conductivity of the composites increases with increasing the weight percentages of fillers, and thermal conductivity of HDPE/Al2O3composites was higher than the other of the composites. Water absorption and diffusivity for the prepared composites, the results show an increasing in water absorption and diffusivity with increasing in the weight percentage, highest values in absorption and diffusivity were recorded for HDPE/Al2O3 composites.