The miscibility of blends of styrene butadiene rubber (SBR) and polyethylene (PE) has been invistigated using positron annihilation lifetime spectroscopy (PALS). The effect of weight percentage of rubber added to pure and waste PE of low and high density (LDPE&HDPE) was investigated. It has been found that, a large hole volume size and concentration in SBR forms a miscible blend with PE, The average ortho-positronium lifetime tau (3) and its intensity I-3 of the blends show a negative deviation from the linear relationship of initial polymers, This could be interpreted in terms of segmental conformation and packing between dissimilar polymers, In addition, a negative correlation between the free-volume parameters (size & concentration) and the electrical and mechanical properties of the prementioned samples has been established as a function of weight percentage of waste PE.