ISO 812:1991 pdf download – Physical testing of rubber
1.1 This International Standard specifies a method for determining the lowest temperature at which rubber materials do not exhibit brittle failure when impacted under specified conditions. Brittleness temperatures thus determined do not necessarily relate to the lowest temperatures at which the material may be used, since brittleness will be modified by the conditions of contact and especially by the rate of impact. Data obtained by this method should therefore be used to predict the behaviour of rubbers at low temperatures only in applications in which the conditions of deformation are similar to those specified in the test.
1.2 Two procedures are described: procedure A, in which the brittleness temperature is determined, and procedure B, in which the test piece is impacted at a specified temperature. The latter procedure is used in the classification of rubber materials and for specification purposes. NOTE 1 A similar test for rubber-coated fabrics is described in ISO 4646:1989, Rubber- or plastics-coated fabrics — Low-temperature impact test.
The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.
Remove the metal guard from around the solenoid. Spread open the rubber bumper (see Figure A.2) and insert it around the armature. Replace the solenoid guard, insert a typical test piece into the specimen holder of the tester. Raise the striking mechanism by hand until the end of the stroke is reached. It is essential that, with the striking mechanism raised to its maximum height, the striker bar of the tester is in contact with the test piece but that the bar is not in the plane of the test piece. If the striker bar is not in contact with the test piece, the rubber bumper shall be removed and replaced by a thinner bumper. Conversely, if the striker bar moves into the plane of the test piece, the bumper shall be replaced by a thicker one.
A.1.2.3 Placement of ball and measuring tube Place a 19 mm diameter steel ball on the ball holder. (In theory, the upward flight of the ball is independent of the mass of the ball. However, if the mass is too large, the motion of the striker bar may be impeded.) Clamp a glass or clear plastics tube with a minimum inside diameter of 25,4 mm in a vertical position directly over the ball. The tube should contain a scale divided into 5 mm intervals. The zero position on the scale should be aligned with the top of the ball when the ball is at the top of the stroke of the striker mechanism.