HAAS - CATALOG 7.5 Strana 356
Nabídka komerčních zákazníků **Nejlépe prodávané z Otto Haas
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RUBBER MATERIALS Determination of degree of hardness hardness grade Applications area acc. to Shore A Product groups Valid test specifications are for Germany DIN 53505, for England British Standard Hardness B.S. 903:19: 1950, for USA ASTM-Hardness 314-39 as well as ASTM D 531-49. Definition 30 ± 5 Printing rollers (Printing house) Rolling rings of driven material 40 ± 5 Rubber bands Sealing rings In rubber technology, hardness means the relative resistance of a sample surface against the penetration of a precisely dimensioned needle under a certain load. As a rule, it is measured for soft rubber according to Shore A grades. The scale ranges from 0-100, where 0 is extremely soft and 100 is extremely hard. This scale almost covers the applications occurring in the soft rubber region. For a better understanding of the following explanations, we give in a table some common hardness values according to Shore A. 50 ± 5 Boil down rings Fermenting cap Bathing cap Pneumatic tire-hoses 60 ± 5 Car- and truck tire running surface Conveyor band Profile Execution of the measurements 70 ± 5 Hoses-Upper rubber Form-soles Full rubber 80 ± 5 Car mats Door buffer Soles and heels Full rubber-tires 90 ± 5 Rubber mallet Floorings Typewriter rollers The standard stipulates that the test shall be carried out on samples which were not subjected to mechanical stress, the test areas (of at least 30 mm diameter) having to be smooth and flat. The thickness of the sample should be at least 6 mm for soft rubber and at least 3 mm for hard rubber. Furthermore, a test should be carried out at about 23 ± 3 ° C and at the earliest 16 hours after vulcanization. It is recommended that at least 3 measurements are taken at different location on the test specimen and the result is determined. The reading of the hardness value shall be made 3 seconds after the surface contact is made. If the rubber article to be measured based on shape or size are not suitable for a flawless Shore hardness measurement (e.g. round, profiled or very thin articles), it is advisable to supply the customer with shaped heated plates from the same mix batch at certain intervals. On these boards, the consumer can carry out technically faultless checks. It is also important that German, American and English standards based on a long practical experience provide for manufacturers and consumers for ± 5 Shore hardness tolerances are binding. This means that a Shore A hardness of 70 (measured with controlled equipment) is required by the user have to be minimum 65 and maximum 75. Statement value of the hardness test according to Shore The most striking feature of the measuring method with a pocket device is that it can be carried out almost quickly on every vulcanizate, that the handset can be carried with it at any time and that the measuring object is not damaged during the measurement. But the simplicity and the enforceability of messure the hardness at any time often lead to an overvaluation and overestimation of the hardness value, whereby the condition of the plane bearing surface of 30 mm diameter is often overlooked. There are sprayed profiles, molded articles, conveyor belts, tire treads, cable coating, rubber membranes, air springs, etc., e.g. together have a Shore hardness of 60 ± 5. This common hardness stands compared with the other attributes, across from many other oppositeness. Abrasion, elasticity, damping, resistance to swelling, tear propagation resistance, etc. may or must be different within these articles. The formulations of the rubber qualities used have little in common, because the special requirements of the application strongly differ from one another. Alone the knowledge of the Shore hardness of an article does not allow for any prediction for the later behavior. Notes for daily practice: • No tighter tolerance than ± 5 Shore hardness points. The inaccuracies associated with the measurement procedure and the irrelevance in the statement value advise to. • Molded and free heated articles of the same quality usually have different hardness values. The articles heated in forms are usually higher by a few points of hardness. • Rubber articles with very different wall thicknesses can Derived statutory units also have different degrees of hardness in themselves. (Insofar as they are modified by the introduction of the SI units and are important for material characterization) The same applies to articles Force Newton N 1 N = 1 kg*m / s2 1 kp = 9,81 N N which, form- and partly are Mechanical Pascal Pa 1 Pa = 1N / m2 1 kp/m2 = 0,0981 Mpa 1 Mpa = 1 N / mm2 free heated. tension • The Shore hardness measureJ Energy Joule J 1 J = 1 kg *m2 / s2 1 kWh = 3,6 MJ ment allows comparative values but does not permit conWork 1 J = 1 Nm 1 erg = 10 –7 J clusions to be drawn about Heat flow volume 1 J = 1 Ws 1 cal = 4,1868 J other elastic properties of the quality. It says nothing or little Power Watt W 1W=1J/s 1 PS = 0,7355 kW kW about the suspension characDensity kilogram by Mg/m3 oder g/cm3 kg/m3 1 g * cm3 { 1000kg/m3 teristics or the compression 3 1 Mg/m cubic meter set. Illustrations, dimensions and descriptions are not binding. We reserve the right to make technical changes! Rubber materials 6
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