and ultimate elongation are made on specimens that have not been prestressed where md and amd mean designate machine draw and against machine draw respectively since the vinyl product is extruded it is tested both parallel to the direction of the draw md and against the direction of the draw amd tensile stress and tensile strength are based on the original cross sectional area of a uniform section of the specimen measurement of tensile set is made after a previously unstressed specimen has been extended and allowed to retract by a prescribed procedure measurement of tensile set after break is also used the tear is calculated pursuant to astm d 624 86 standard test method for rubber property tear resistance approved mar 27 1986 this test method uses three independent specimen shapes namely a razor nicked crescent specimen die a a razor nicked crescent specimen with tab ends die b and an unnicked 90 u00b0 angle specimen die c to determine the tear resistance valve again the designation md is in the machine draw direction of the material and amd is the against machine draw direction of the material the hardness is calculated pursuant to astm d 2240 86 standard test method for rubber property durometer hardness approved mar 27 1986 this test method covers type a durometers used for testing softer materials and the procedure for determining the indentation hardness of homogeneous materials ranging from soft vulcanized rubber to some plastics this test method permits hardness measurements based on either initial indentation or indentation after specified periods of time or both each of the above identified standard test methods namely astm d792 86 astm d 747 86 astm d 792 86 astm d 412 87 astm d 624 86 and astm d 2240 86 are incorporated.