What is Compression Deflection and Compression Set?

When beginning a new project, PGC engineers consider many factors to determine the best materials for a particular application. Sealing solutions may require elastomeric materials due to their unique ability to compress. Two key characteristics that enable this are the compression deflection and compression set. Compression deflection measures a material's resistance to force applied to a surface area over a controlled distance. Compression set is the amount of deformation of a material after the removal of the force. It's common to use ASTM D2000 when measuring solid rubber materials, while it's best to use ASTM D1056 for cellular rubber materials.

Why is compression deflection and set important?

Understanding how an elastomeric material will behave is essential for selecting the correct material for a specific application. This can be challenging because thousands of elastomers exist in different solid or cellular formats. It is necessary to narrow down the options by understanding the critical properties of each material and knowing which ones will apply best to the application. Another important consideration is the surface on which the material is used, as the performance of a specific material can vary based on how it performs once it's sealed.

Types of Elastomer Materials

There are two main types of elastomer materials: solid rubber and cellular rubber. Solid rubber is not commonly used in sealing applications because it does not change volume when compressed and tends to exhibit cold-flow behaviors, which are unsuitable for long-term sealing performance. Cellular materials are a much better choice for such applications because they can compress more efficiently and offer less resistance to loading.

Choosing the Correct Material

When choosing materials for gasket and sealing applications, it is crucial to select the appropriate thickness. Thicker materials are more costly and increase the risk of developing leaks, while too-thin materials may not provide enough force to seal and resist the pressures encountered by the gasket or seal.

Align your compression deflection requirements with the Technical Data Sheet (TDS) results. This will help optimize the part's ability to exert enough sealing force and prevent the material's compression set behaviors from affecting the part's performance over time. All elastomeric materials compress to some extent over time, so choosing materials that apply sufficient force against the connector while staying below the material's compression set limit is essential. Doing so will ensure that the material can meet your application's performance needs throughout the product's life.