the invention pertains to electrical insulation formed from a normally solid , linear olefin polymer containing from about 1 to about 20 percent by weight of chlorine chemically combined therewith , said polymer having a bulk density of from about 22 to about 36 pounds per cubic foot and wherein the individual polymer particles are predominantly in the range of from about 300 to about 800 microns in size , a melt index of from about 0 . 05 to about 2 as determined by astm test no . d1238 , procedure a and a tensile yield strength of greater than about 1000 p . s . i . the specified polymers have enhanced processability as compared to conventionally used nonchlorinated or highly chlorinated olefin polymers and may be effectively dry blended with additives such as stabilizers , blowing agents and fillers . electrical insulation formed from such polymers is characterized by smooth surfaces , high stress crack resistance and excellent electrical properties as well as unexpectedly improved response to cross - linking by exposure to atomic radiation , with resultant high resistance to thermal and / or oxidative - induced degradation .