invention is calcium stearate the radiation exposure may be from for example co 60 gamma radiation or lower level radiation such as that from e beam radiation the radiation exposure may be that used in sterilization techniques for medical or food handling applications the materials of the invention may have application where radiation exposure is usually in the range of 1 6 mega rads mrads ziegler natta catalysts also useful in the preparation of isotactic polypropylene are typically derived from a halide of a transition metal such as titanium chromium or vanadium with a metal hydride and or metal alkyl typically an organoaluminum compound as a co catalyst the catalyst is usually comprised of a titanium halide supported on a magnesium compound ziegler natta catalysts such as titanium tetrachloride ticl 4 supported on an active magnesium dihalide such as magnesium dichloride or magnesium dibromide as disclosed for example in u s pat nos 4 298 718 and 4 544 717 both to mayr et al and which are fully incorporated herein by reference are supported catalysts silica may also be used as a support the supported catalyst may be employed in conjunction with a co catalyst or electron donor such as an alkylaluminum compound for example triethylaluminum teai trimethyl aluminum tma and triisobutyl aluminum tibai ziegler natta catalyst systems incorporating diethers and succinates may also be used with the invention the isotactic polypropylene used in the present invention may be a propylene homopolymer which may be prepared from either ziegler natta or metallocene catalyst useful in preparing istotactic polymers as used herein u201c homopolymer u201d shall mean those polymers having less than about 0 1 by weight of polymer of other comonomers the isotactic polypropylene component employed will typically have a meso dyad content as.