The surface properties of plastics containing silicones or of silicone-based thermoplastics are modified in several ways. for example, by conventional compounding, extrusion or coextrusion (blown or cast extrusion). Through varying the silicone-based GENIOMER^® content in the extrudate or coextrudate, the silicone nature of the surface can be tailored to produce the required degree of release, hydrophobicity or haptics.