Project Description

Rubber Compression Set Test Apparatus

Compression set of Rubber Silicone EPDM

Rubber Compression Set Test Fixture is used to determine the deformation rate of vulcanized rubber, thermoplastics silicone subjected to the specified compression deflection at room temperature, low temperature and high temperature after a certain period of compression time. When the rubber is compressed for an extended period of time, it will lose the ability to return to its original thickness. This loss of resiliency is also called permanent set.

Compression Set Testing can determine the capability of rubber to go back to its original thickness after the prolonged compressive force at a specified temperature and deflection.  Because the rubber material loses its capability to return to its original thickness once subjected to compression, this loss of resiliency might decrease the functional performance of an elastomeric gasket, seal or cushioning pad over an extended time.

This is an indispensable device to conduct the compression deflection test. Compression set outcomes are expressed as a percentage figure. The lower the percentage figure, the better the product resists permanent contortion under a given deflection and temperature range.

Test Principle

Place the standard rubber test specimens on the parallel steel plates, then put the steel spacers with the required percentage of compression to control their thickness while compressed. Nuts on the surface of the top plate are screwed in succession to compress the specimen uniformly to a specified height(test specimens and spacers can’t contact each other while compressed). Place the assembled compression device with samples in an aging oven and store it at a given temperature for a specified time, then take it out for cooling for 30 min. Measure the final thickness to calculate the permanent deformation rate by means of the given equation.


Test Standards

ASTM D395, Method B Compression Set Under Constant Deflection in Air
GB/T 7759, JIS-K6262, JIS-K6301, DIN ISO-815, DIN 53517, CNS-3560, CNS10487, etc.

Main Technical Parameters

Model AT-R7020
Type Rectangle
Specimen Type A Diameter: 29 ± 0.5 mm | Height: 12.5 ± 0.5 mm
Specimen Type B Diameter: 13 ± 0.5 mm | Height: 6.3 ± 0.3 mm
Heights of the Spacer 4.5 mm, 5 mm, 7.6 mm, 8.9 mm, 9.5 mm, 10.2 mm, 12.5 mm or user’s choice
Plate Dimension 200 mm ( W )  x 120 mm ( D ) x 15 mm ( H )
Plate Material Stainless steel
Steel Plates 3 pcs (2 layers)
Weight 15 kg

Rubber Compression Set Apparatus Features

  • It consists of parallel steel plates, spacers, fasteners made of premium steel.
  • The fixture complies with ASTM, JIS, DIN, etc., international standards.
  • Compatible with ambient temperature, low temperature and high temperature.
  • Different sizes of the spacer are available to match different types of specimens.
  • Three different steel plates form a 2-layer testing area.


  • Rubber Thickness Gauge and Laboratory Air Oven need to be purchased extra for completion of this test.
  • Compression time is 24h, 72h, 168h or the integral multiples of 168h. It’s best to choose 24h or 72h for low temperature.

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