Rubber

Rubbers and elastomers are polymers that exhibit a degree of viscoelasticity and possess the ability to undergo large deformation while under stress and still be able to return to their original shape when the material is unloaded. Because of their unique characteristics elastomers and rubbers have a wide range of uses including but not limited to seals, belts, restraints, bands, stoppers, coatings, and vibration dampeners. These products are often used in the automotive, medical and other similar industries due to their flexibility and strength.

Rubber and Elastomer Testing Goal:

Testing rubber and elastomer determines whether they may be used in specific applications. Normally rubber is used in situations that require a product capable of large amounts of deformation and still be able to return to their original shapes afterwards. To test for this characteristic the materials are tested in tension, compression, adhesion and impact to determine the elastic modulus, the tensile and compressive strength, the elongation or reduction of area at break, how it will respond to shock forces and the adhesion force between the elastomer and reinforcing material. These characteristics define the expected limits of the material samples tested, which gives a depiction of how the rubber or elastomer will behave under stress.

Common Rubber Test Methods:

Rubber and elastomers are tested using various tension, compression, and adhesion tests. These tests are similar to those performed on other materials, but the key difference is in the control of the environment. The properties of rubber and elastomers change sometimes significantly depending on their temperature, ozone and fluid exposure and age. It is very important to test these materials under the proper conditions as the measured values may be different from those that the material will exhibit during its application. For example some elastomers will crystallize at low enough temperatures, which will result in the nature of the material changing from very ductile to very brittle and will significantly lower its tensile strength and elasticity.

Rubber and Elastomer Testing Specimens:

Test samples made from rubber and elastomer can take many different shapes but are usually formed by either using a die cutter to cut the sample from a sheet of the material like using a cookie cutter or by using a mold and pouring or pressing the material into the desired shape. The shape these test samples can take range from dog bones for tensile testing to butterflies for tear testing to spheres or cylinders for compression and impact testing among many others. Once the specimens have acquired the proper shape they must be prepared according to the required specifications of the test procedure. This generally involves heating or cooling the sample to a desired temperature, allowing it to age, or exposing it to a predetermined amount of air, sunlight, or fluid. These variables are used to alter the characteristics and properties of the test specimen in order to properly observe the reaction the material will show during the conditions of its application.

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Applicable Standards

• ASTM D1229 Rubber Compression Set Test Equipment
• ASTM D1414 Tension testing and tension set of Rubber O-Rings
• ASTM D1871 Adhesion Between Tire Bead Wire and Rubber
• ASTM D2229 Adhesion Between Steel Tire Cords and Rubber Test Equipment
• ASTM D395 Compression of Rubber in Air or Liquid Test Equipment
• ASTM D412 Tension Testing for Rubber and Elastomers
• ASTM D413 Peel Adhesion of Rubber to Flexible Substrate
• ASTM D429 Rubber to Metal Adhesion Test Equipment
• ASTM D575 Compression Test of Rubber
• ISO 34-1 & ISO 34-2 Tear Strength of Rubber, Vulcanized or Thermoplastic - Trouser
• ISO 6133 Rubber Tear and Adhesion Strength