rubber component may be incorporated into the nitrile containing polymer by any of the methods which are well known to those skilled in the art e g direct polymerization of monomers polyblends grafting the acrylonitrile monomer mixture onto the rubber backbone etc especially preferred are polyblends derived by mixing a graft copolymer of acrylonitrile and comonomer on the rubber backbone with another copolymer of acrylonitrile and the same comonomer generally such rubber component may comprise from 0 to about 25 and preferably up to about 10 by weight of the nitrile polymer composition the manner in which the polyethylene modifier is added to the nitrile polymer composition is not critical and it may be added to the polymer in bead or powder form and may also be added in combination with other additives such as formaldehyde compounds as disclosed in u s pat nos 3 870 802 and glycerol or sorbitan ester modifiers as disclosed in 3 931 074 the following examples are set forth in illustration of the present invention and are not to be construed as limitations thereof a nitrile composition comprising 90 by weight of methacrylonitrile and 10 styrene was compounded with 440 ppm of polyethylene having a molecular weight of about 9000 the compounded composition was then extruded in a c w brabender 3 4 inch extruder at a melt stock temperature of 250 u00b0 c an.