Durometer hardness of rubbers

Test method for indentation hardness of rubbers, international hardness Test for Durometer hardness of rubbers... 

The standard test method for measuring the durometer hardness of rubbers according to ASTM D2240-05 [6] is based on the penetration of a specified indentor forced into the material under specified conditions. The indentation hardness is inversely related to the penetration and is dependent on the elastic modulus and viscoelastic behaviour of the material. This method is an empirical test intended primarily for control purposes. No simple relationship exists between indentation hardness determined by this method and any fundamental property of the material tested. 

Durometer - An instrument for measuring the hardness of rubber. The "A" durometer scale is used for flexible materials and the "D" for rigids. 

Natural rubbers, such as pure gum with a durometer hardness of 40 on the Shore A scale, display surprising long life in sliding abrasion. Such linings are used in sand and slurry handling pumps and pipings where particles are in fine size and no grit is present. 

ASTM D2240. 1975. Indentation Hardness of Rubber and Plastics by Means of a Durometer. 

Durometer du- ra-m9-t9r also dyu [L durus hard] (ca. 1879) n. An instrument used for measuring the hardness of rubber, plastic, or protective coatings. 

Carbon black is by far the most important filler and reinforcement agent used in rubber compounding. It is commonly used with processing oil (the black oil balance) to control the durometer hardness of the rubber compound. Carbon black is many times used with oil to reduce the cost of the compound because carbon black and process oil are usually less expensive per pound than many raw elastomers. Also, carbon black is essential for compound reinforcement, for improvement in compound physical properties such as ultimate tensile strength, abrasion, wear, and tear resistance. 

Hardness - Hardness, as applied to rubber products, is the relative resistance of the surface to indentation under specified conditions. Hardness of rubber is usually measured with a small spring-loaded hardness gauge known as a durometer (ASTM D-2240). The durometer may be handheld or mounted on a stand. The measurement is made by pressing the indentor against the sample and reading the scale, which is calibrated in arbitrary units ranging from 0 (soft) to 100 (hard). A Type A durometer is used for most soft rubber products there is also a Type D durometer for hard rubber and plastic-like materials. On the A scale, a gum rubber band would measure around 40, a tire tread 60, and a shoe sole 80. 

The hardness range of this class of materials is from 60 Shore A to 60 Shore D. Hardness, modulus and tensile strength all increase as the PP content increases. (The hardness of rubber compounds is typically measured by the Shore Durometer test an indentor is pressed into the material, under a specified load, and the amount of penetration determines the hardness. A circular tip is used for the A scale and a pointed tip is used for the D scale. D means harder materids.)... 

Recommended Practice for Scleroscopic Hardness Testing of Metallic Materials Test Method for Rubber Property International Hardness Test Method for Rubber Property Durometer Hardness... 

International Rubber Hardness. The International mbber hardness test (ASTM D1415) (2) for elastomers is similar to the Rockwell test ia that the measured property is the difference ia penetration of a standard steel ball between minor and major loads. The viscoelastic properties of elastomers require that a load appHcation time, usually 30 seconds, be a part of the test procedure. The hardness number is read directly on a scale of 0 to 100 upon return to the minor load. International mbber hardness numbers are often considered equivalent to Durometer hardness numbers but differences ia iadenters, loads, and test time preclude such a relationship. 

An instrument for the determination of the hardness of vulcanised rubber. The name is usually, but not necessarily, applied to a pocket-type instrument made by the Shore Instrument and Manufacturing Co. Inc. The use of the term in the sense of hardness (a durometer of 60°) is not recommended. 

Durometer hardness - A value that indicates the indentation or resistance to indentation of the indentor point of a durometer. High values indicate harder materials. See ASTM D2280-Test Method for Rubber Property-durometer Hardness. 

Standard test method for rubber property Durometer hardness Shore A and Shore D hardness testing of rubber Physical testing of rubber Part A57... 

Durometer hardness is measured on tests specimens that meet specific standards for shape and thickness. Durometer hardness is usually measured using the Shore A scale, which measures relative hardness on a scale of 0 to 100 units. Most rubber components for medical use are found in the 35-60 range with 40-50 typical for rubber vial stoppers. Durometer Hardness may be measured on some actual components if they have a sufficiently large flat surface and thickness, i.e., 28-32 mm IV stoppers. 

Since the flow causes sliding abrasion at a low angle of incidence in the piping, the rubber which can be suggested for this application is a low durometer hardness (40 on the Shore A scale) natural rubber. For lower flow rates at ranges of 1,200 litres per minute up to 4,000 litres per minute, a hard rubber or a semi-ebonite rubber can be used since the abrasive wear of the finely meshed particles will be negligible. 

The Shore A scale, or as it is sometimes called, durometer hardness, enjoys considerable success in North America and in particular is widely accepted by the automotive industry the scale is an integral part of the classification system for elastomeric materials used in automotive applications (ASTM D2000). Shore hardness has also become the industry standard for the rapidly growing thermoplastic rubber sector, where advantage can be taken of the complementary Shore D scale for harder grades and for rubber-modified plastics. Seven Shore scales are described in ASTM D2240, while Shore A and D hardness are also detailed in the international standard for pocket hardness meters. ISO 7619 (BS903. Part A57). The latter also specifies a pocket meter based on the IRHD scale. 

Since most silicone adhesives and sealants are elastomeric in nature, their physical property testing often parallels classical rubber testing approaches. Common tests include durometer, tensile strength, elongation, and modulus. Several methods are available for the measurement of rubber properties, but the most commonly used are the American Society for Testing and Materials (ASTM) D-412, Test Method for Rubber Properties in Tension, and the ASTM C-661, Standard Test for Indentation Hardness of Elastomeric-Type Sealants by Means of a Durometer. These properties vary widely with the product... 

The Lambda series of Medicaflex is a polyurethane-based TPE polymer that exhibits low modulus characteristics with high tear strength and abrasion resistance. Those listed in the tables have passed USP Class VI compatibility tests and have been used as replacements in some natural rubber latex and silicone rubber applications. The polymer has been applied to uses such as catheters, tubing and films where softness, low durometer hardness, low modulus or high elongation are needed (Tables 4.3, 4.12, and 4.13). 

D 1790 Test method for Brittleness Temperature of Plastic Film by Impact D 1938 Test method for Tear Propagation Resistance of Plastic Film and Thin Sheeting by a Single-Tear Method D 2240 Test Method for Rubber Property - Durometer Hardness D 2702 Standard Practice for Rubber Chemicals - Determination of Infrared Absorption Characteristics... 

The resistance of rubber to deformation is known as hardness and is measured by an instrument known as a durometer, made by the Shore Instrument Company. There are several Shore instruments, namely, A, B, C, D, and O. Each is designed to give different readings from soft sponge up to ebonite-type materials. For elastomeric materials Shore A is the commonly used scale with 0 being soft and 100 hard. By comparison a rubber band would have a reading of approximately 35 and a rubber tire tread 70. 

This is an industrial grade of natural rubber with better tear resistance but slightly lower abrasion resistance than natural rubber. It typically has durometer hardness 45-Shore hardness A. Its temperature limit is 82°C (180°F). This form of filled natural rubber is widely used in the industrial, mining, and utilities industries. 

Standard test method for rubber properly-durometer hardness, ASTM Standard, Book of Standards, Vol. 09.01 ASTM D 2240-05, ASTM International, West Conshohocken, PA, 2005. 

Hardness of an adhesive is not important in itself, but for the sealant it may be important because it may be damaged if it is too soft, for instance, when the sealant joint is on the floor and should withstand traffic. Hardness is measured in a classic way as rubber hardness with a Shore durometer. There are of course relationships between hardness, flexibility, stiffness, etc. Hardness may also be used sometimes as an indication of the degree of cure. 

The hardness of plastics (and coatings may be considered to be very thin plastics) is most commonly measured by the Shore (durometer) test or Rockwell hardness test. Both of these hardness methods measure the resistance of plastics toward indentation. This provides an empirical hardness value. Shore hardness most often uses either the Shore A or the Shore D scale. These methods are best used for rubbers or elastomers and are also commonly used for softer plastics such as polyolefins, lluoropolymers, and polyvinyls. The Shore A scale is used for softer rubbers while the Shore D scale is used for harder ones. This method works better for thicker coatings, as with all hardness tests on coatings. The hardness of thin coatings can be influenced by the substrate, that is, an artificially hard measure may be measured. A picture of a durometer is shown in Fig. 2.23. 

---