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Compression Set (CS)
The Compression Set of elastomers is the deformation that remains when the applied force is removed. When elastomers are compressed over a period of time, they cannot retain their initial thickness.
CS tests can measure the ability of a rubber sample to return to its initial thickness after compression pressure is applied at a set temperature and deflection.
Importance
CS is important for sealing functionality and achieving long term sealing. CS measurements are also critical to determine the quality of the elastomeric material. Take the example of a shock isolation pad, where the ability to protect a dropped unit could be compromised as the CS measurement becomes more important.
Compression Set Measurement
A rubber sample that has zero CS will return to 100% of its initial thickness, whereas the sample that has 100% CS is the one that does not return to its initial thickness.
The CS (ASTM D395) of a sample is determined by using one of two tests.
1) Test Method A
CS under continuous force in the air usually applies 1.8kN force to the sample for a set temperature and time.
2) Test Method B
CS under continuous deflection in the air can compress the sample to 25% of its initial height for a set temperature and time.
CS tests A and B can be defined as the percentage of initial sample thickness after it has been subjected to normal conditions for at least 30 minutes.
O-ring CS testing is conducted using the ASTM D1414 B method.
Calculating Compression Set
Measuring the CS for a sample can be achieved using specific formulae, ideal for each testing method.
O-ring CS testing is conducted using the ASTM D1414 B method.
1) Test Method A
CA = [(to – ti) / to] * 100
Where,
CA – Compression set A
to – Initial sample thickness
ti – Sample thickness after testing
2) Test Method B
CB = [(to – ti) / (to – tn)] * 100
Where,
CB – Compression set B
to – Initial sample thickness
ti – Sample thickness after testing
tn – Sample thickness during testing
Compression Set (CS)
The Compression Set of elastomers is the deformation that remains when the applied force is removed. When elastomers are compressed over a period of time, they cannot retain their initial thickness.
CS tests can measure the ability of a rubber sample to return to its initial thickness after compression pressure is applied at a set temperature and deflection.
Importance
CS is important for sealing functionality and achieving long term sealing. CS measurements are also critical to determine the quality of the elastomeric material. Take the example of a shock isolation pad, where the ability to protect a dropped unit could be compromised as the CS measurement becomes more important.
Compression Set Measurement
A rubber sample that has zero CS will return to 100% of its initial thickness, whereas the sample that has 100% CS is the one that does not return to its initial thickness.
The CS (ASTM D395) of a sample is determined by using one of two tests.
1) Test Method A
CS under continuous force in the air usually applies 1.8kN force to the sample for a set temperature and time.
2) Test Method B
CS under continuous deflection in the air can compress the sample to 25% of its initial height for a set temperature and time.
CS tests A and B can be defined as the percentage of initial sample thickness after it has been subjected to normal conditions for at least 30 minutes.
O-ring CS testing is conducted using the ASTM D1414 B method.
Calculating Compression Set
Measuring the CS for a sample can be achieved using specific formulae, ideal for each testing method.
O-ring CS testing is conducted using the ASTM D1414 B method.
1) Test Method A
CA = [(to – ti) / to] * 100
Where,
CA – Compression set A
to – Initial sample thickness
ti – Sample thickness after testing
2) Test Method B
CB = [(to – ti) / (to – tn)] * 100
Where,
CB – Compression set B
to – Initial sample thickness
ti – Sample thickness after testing
tn – Sample thickness during testing
NEED HELP?
Speak with a human to filling out a form? call corporate office and we will connect you with a team member who can help.
