Hello~! We are SALT CO., LTD. a specialized manufacturer of material testing machines.

Today, we would like to introduce ASTM D395, a standard test method for measuring the compression set of rubber.

What is ASTM D395?

ASTM D395, titled "Standard Test Methods for Rubber Property—Compression Set," describes the test method used to measure the compression deformation characteristics of rubber. 

This test method evaluates the elasticity and permanent deformation characteristics of rubber by measuring how much it recovers when compressed. This standard covers two test methods:

A - Compression set under constant force in air

B - Compression set under constant strain in air

The choice of test method is optional, but consideration should be given to the service conditions where correlation of test results can be found. Unless otherwise specified in detailed specifications, Test Method B should be used. In today's post, we will focus on Test Method B.

Principle of the Test:

Compression deformation rate testing is a commonly of interest when using rubber. 

Compression set is the amount of permanent deformation that occurs when a material is compressed to a specified deformation for a specified time and temperature. 

In the test method described in ASTM D395, the material should be compressed by 25% for a specified period. Measurements are taken after a recovery time of 30 minutes. 

The result is the percentage of the original height that the material fails to recover. For example, 40% compression set indicates that a thermosetting elastomer recovers only 60% of its uncompressed thickness. 

A 100% compression set means that the thermosetting elastomer does not recover at all, remaining in the compressed state.

Comparison between ASTM D395 and ISO 815

Salt's Permanent Compression Set Tester ST-180

Salt's ST-180 Permanent Compression Set Tester

This equipment is used to measure the permanent compression rate by compressing polyurethane and rubber test specimens to a certain height, maintaining them at a specified temperature for a specified time, and comparing the deformed height (length) before and after recovery. The measurement value is expressed as a percentage by calculating the difference between the initial thickness of the test specimen and the thickness after recovery.

Manufactured based on ASTM D395, ISO 815.

Custom orders are available to accommodate various sizes of spacers for different types of specimens.

Made of SKD special steel with minimal thermal deformation, ensuring stability even under high-temperature conditions.

Precision Spacer (Resolution ±0.001mm)

8 spacers provided per set

Salt Co., Ltd.'s all-purpose material tester provides a variety of grips, 

extensometers and test solutions to meet the requirements of physical property testing of various materials.

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