Prepare an oriented polymer composition that is cavitated, has cross sectional dimensions all at least three millimeters and at least one de-oriented surface layer having a thickness of at least 80 microns and at least 50 microns less than half the thickness of the oriented polymer composition, the de-oriented surface layer having a lower degree of polymer orientation than a 100 micron thick portion of the oriented polymer composition adjacent to and below the de-oriented surface layer by sufficiently heat treating a surface of a cavitated oriented polymer composition.