Hardness
Hardness is one of the most widely measured properties to characterise rubber. There are 2 scales against which hardness is measured – the IRHD (International Rubber Hardness Degree) scale and the Shore scale. A variety of instruments exist for both scale types, including bench mounted and hand held, of which Ultratest are able to offer both types – please see details below.
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Work has been done looking at these 2 scales and each features its own merits. The IRHD method is often preferred for its non-destructive nature; the Shore method for its significantly shorter test time.
The IRHD method is based on the use of dead loads (usually weights) whilst the Shore Method uses calibrated springs. The IRHD method consists of applying a primary load for 5 seconds which provides a datum point from which to measure the indentation from the secondary load, which is applied for 30 seconds. In contrast, the Shore Method uses a presser foot to contact the sample and the indentation depth is recorded after a pre-set time of typically 1 or 3 seconds.
A variety of instruments exist for both scale types, including bench mounted and hand held, of which Ultratest are able to offer both types – please see details below/alongside.
The IRHD method features both a dead load model and a scaled down micro version for testing thinner samples. The Shore method features a range of scales to test a wide variety of rubber, plastic and sponge samples. Typically, the most commonly used within the rubber industry are the Shore A, Shore D (for hard rubber and plastics) and Shore M (for thin sections). A selection of the instruments that Ultratest offer can be found above, but please contact us to discuss your specific testing requirements.
Hardness testers may be used to check a specially prepared sample of a defined thickness or they can be used to test the hardness of final products. When testing final products, such as O-rings, it is important to test at the top dead centre so that a true hardness value is achieved. In order to make this easier, it is possible to purchase an O ring clamping device to hold it accurately in the correct location for testing, details of which may be found alongside each of the hardness testing instruments.
It is recommended that testing machines are calibrated annually and as such Ultratest offer on–site service and calibration. In addition, it is recommended that instruments are checked regularly using certified test blocks.
The IRHD method is based on the use of dead loads (usually weights) whilst the Shore Method uses calibrated springs. The IRHD method consists of applying a primary load for 5 seconds which provides a datum point from which to measure the indentation from the secondary load, which is applied for 30 seconds. In contrast, the Shore Method uses a presser foot to contact the sample and the indentation depth is recorded after a pre-set time of typically 1 or 3 seconds.
A variety of instruments exist for both scale types, including bench mounted and hand held, of which Ultratest are able to offer both types – please see details below/alongside.
The IRHD method features both a dead load model and a scaled down micro version for testing thinner samples. The Shore method features a range of scales to test a wide variety of rubber, plastic and sponge samples. Typically, the most commonly used within the rubber industry are the Shore A, Shore D (for hard rubber and plastics) and Shore M (for thin sections). A selection of the instruments that Ultratest offer can be found above, but please contact us to discuss your specific testing requirements.
Hardness testers may be used to check a specially prepared sample of a defined thickness or they can be used to test the hardness of final products. When testing final products, such as O-rings, it is important to test at the top dead centre so that a true hardness value is achieved. In order to make this easier, it is possible to purchase an O ring clamping device to hold it accurately in the correct location for testing, details of which may be found alongside each of the hardness testing instruments.
It is recommended that testing machines are calibrated annually and as such Ultratest offer on–site service and calibration. In addition, it is recommended that instruments are checked regularly using certified test blocks.