ASTM D395 Standard Test Methods for Rubber Property-Compression Set

    What is ASTM D395?

    ASTM D395 provides test methods for the compression set of rubber materials. The processes involve compressing the rubber specimen under specific conditions and then measuring the permanent deformation after the compressive force is removed. The standard specifies different methods and test conditions for compression set. The methods assess the permanent deformation that remains in the rubber specimen after compression and conditioning. There are three test methods described in ASTM D395: A-Compression Set Under Constant Force in Air; B-Compression Set Under Constant Deflection in Air; and C-Compression Set Under Constant Deflection in Air Considering Material Hardness. The choice of test method depends on the requirement; however, B is the most commonly used method. Laboratories use ASTM D395 (Standard Test Methods for Rubber Property—Compression Set) to determine the recovery of rubber materials after compression and to support comparisons of rubber materials, quality control, and product development. Engineers use the results to determine a rubber material’s ability to recover from long-term or controlled compression.

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    Get Certified ASTM D395 Testing for Reliable Rubber Compression Set

    Rubber parts are often under compression during use. Therefore, the compression set test helps engineers determine whether a rubber material will retain its shape and sealing properties when compressed. ASTM D395 (Standard Test Methods for Rubber Property—Compression Set) is a standard method for measuring permanent deformation following compression. These results aid in the selection of materials, quality control, product development, and the comparison of rubber formulations.

    What is the Scope of the ASTM D395 Test Standard?

    ASTM D395 measures the compression set of vulcanized rubber and thermoplastic elastomeric materials. It measures the permanent deformation after a specimen is subjected to specified compression and conditioning. The ASTM D395 standard-

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    • Measures compression set (defined) of rubber materials.
    • Assesses permanent deformations after compression.
    • Carries out compression and conditioning processes as required.
    • Enables assessment of rubber recovery.
    • Assists in comparing rubber formulations.
    • Assists in the quality control of rubber products.
    • Assists in the assessment of materials for compression-service applications.

    What are the Uses of ASTM D395 Testing?

    Laboratories use ASTM D395 testing to assess the resiliency of rubber materials after compression. Engineers use the results to compare materials and determine their suitability for situations where they are under constant compression. This standard-

    • Determines compression set.
    • Evaluates permanent deformation.
    • Assists in comparing rubber materials.
    • Helps in gasket/sealing-material evaluation.
    • Assists in evaluating material recovery.
    • Assists in the development and quality control of products.
    • Provides information for material selection.

    Which materials can be tested under ASTM D395?

    ASTM D395 is applicable to vulcanized rubber and thermoplastic elastomeric materials that can be tested in accordance with the compression-set procedures specified. Materials can be assessed in various forms, provided they meet the applicable specimen requirements. The test method and conditions depend on the material being evaluated and the purpose of the evaluation.

    Why is ASTM D395 Important?

    Permanent deformation of rubber after compression is evaluated by ASTM D395. This property helps engineers determine a material’s potential performance under compression during service. The results can also help manufacturers compare different formulations and choose rubber materials for applications that require recovery and dimensional stability.

    ASTM D395 Equipment and Sample Preparation Guide

    ASTM D395 specifies compression fixtures and controlled conditioning equipment appropriate to the test method used. Rubber samples with the specified dimensions are prepared in the laboratories prior to compression.

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    Sample and Specimen DetailsRepresentative rubber specimens are prepared in accordance with the applicable ASTM D395 method and specimen requirements and tested in the laboratories.
    Specimen PreparationTechnicians prepare specimens with smooth, uniform surfaces and measure their initial dimensions before compression testing.
    Specimen DimensionsTechnicians select specimen dimensions according to the ASTM D395 method and applicable specimen configuration.
    InstrumentationCompression fixtures, spacers, thickness-measuring equipment, oven or controlled-temperature chamber, and suitable dimensional measurement equipment support the test.

    Testing Procedures and Requirements for ASTM D395

    ASTM D395 is a compression test that compresses rubber samples by a specific amount and then places them under controlled conditions. Technicians remove the specimens after the conditioning period required and measure recovery; the complete procedure is as follows-

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    Initial MeasurementThe specimen thickness is measured before compression.
    Specimen CompressionThe operator inserts the specimen into the compression fixture with the given deformation.
    ConditioningThe specimen is compressed and held for the specified time and temperature.
    Recovery MeasurementTechnicians remove the specimen from compression and, after an appropriate recovery period, measure its thickness.
    Result ReportingThe compression set is calculated as a percentage, and the report includes test conditions and specimen information.

    ASTM D395 Testing Process and Data Collection

    Analysts take rubber samples and select the most suitable ASTM D395 method and appropriate conditioning conditions. Next, technicians measure the initial specimen thickness, then place each specimen in the compression fixture. The operator then compresses the specimen as specified and keeps the specimen at the specified temperature and time. Technicians remove the specimens from conditioning and allow them to recover for the specified period. Finally, technicians measure the recovered thickness and compression set, and analysts calculate the results. Several samples may be tested to check the uniformity of the rubber material.

    This image shows rubber specimens compressed in a fixture for evaluating compression set according to ASTM D395.
    ASTM D395 Compression Set Testing of Rubber

    Common Challenges and Troubleshooting

    Accurate ASTM D395 results require consistent specimen dimensions, controlled compression, stable temperature, and accurate thickness measurements. Measuring permanent deformation can be influenced by improper compression/conditioning. Technicians should verify the compression fixtures and specimen dimensions before testing. Laboratories also need to obtain reliable results with consistent conditioning and accurate recovery measurements.

    ASTM D395 Analysis Results and Interpretation

    The report summarizes the permanent set of the rubber specimen after the specified compression and conditioning. Laboratories report compression set as a percentage of the original specimen deformation.

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    • ASTM D395 yields compression-set values instead of a single strength value.
    • The compression set is expressed as a percentage (%).
    • A lower compression-set value is generally a sign of better recovery following compression.
    • The laboratory records the test method, temperature, conditioning time, and specimen information.
    • Several specimens can be used to determine the material’s consistency.
    • Laboratories can provide reliable results if they compress and condition at the same conditions every time.

    Link to ASTM D395

    FAQ

    Where can I get the astm d395 tested?
    You can share your astm d395 testing requirements with MaTestLab. MaTestLab has a vast network of material testing laboratories, spread across the USA and Canada. We support your all material testing needs ranging from specific astm d395 test to various testing techniques.
    Please contact us for a detailed quote for your astm d395 testing needs. Cost incurred to carry out different astm d395 testing methodology depends on the type of raw material; number of samples, coupons, or specimens; test conditions, turn around time etc. Costs of some ASTM testing methods start from $100 and the final value depends upon the factors listed above. Please contact us for the best and latest prices.
    The required number of samples or specimens should comply with the procedure given in the astm d395 standard. However, the MaTestLab operations team can assist you for your special requirements once you share your testing details with us.
    MaTestLab has a vast testing laboratory network, hence we bring you the best testing facilities in a cost-effective way. We offer considerable discounts (15-20%) to our returning customers based on test volume and frequency.
    The turnaround time for astm d395 test methodology depends upon the test procedure mentioned in the standard test document. However, we at MaTestLab understand your research requirements and hence try to get your test completed within the least possible time.
    Gokula Srinivasan Selvam
    About Author
    Gokula Srinivasan Selvam
    Gokula Srinivasan Selvam is a Material Testing Associate at MaTestLab Inc. and holds a postgraduate degree in Ceramic Engineering from IIT (BHU), Varanasi.
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