Polyurethanes Compression Set
The compressibility of elastomeric materials often makes them an ideal choice for many applications that require sealing or significant pressure. However, not all materials will behave the same. Many elastomeric materials tend to lose their elastic memory on impact, making it difficult to spring back and perform appropriately after experiencing compressive forces. Understanding the compression set requirements of your product design may help shape your material selection. In this post, we will discuss the compression set of thermoset polyurethanes compared to other materials.
What is Compression Set?
A compression set is a material’s ability to withstand compressive forces. For example, silly putty displays high compression as it can replicate any object or fingers once squeezed or poked – losing their ability to recover to its original shape. Products with low compression, like foam bumper pads or mattresses, can display much greater recovery.
How to Measure Compression Set
Compression set values are usually measured by the percentage loss in thickness caused by the compressive force. This process typically involves a material specimen compressed between two objects for a set time, then released and left to recover. Measurements are often performed after a specific period to calculate the material’s compression set. The lower the percentage, the greater the material can resist permanent deformation and offer extended performance. Test results may differ from the actual load a product will experience in application but will provide comparative data to inform your design decisions. For accurate results, there are standardized testing methods, such as ASTM D395, often employed in lab environments to measure compression sets.
Polyurethane Compression Set Compared to Other Materials
A material’s compression set can vary based on several factors, including but not limited to its molecular chemical structure, environmental conditions, and applied force. However, materials like thermoset polyurethanes can offer product designers controlled results and unlimited design freedom. Due to their adaptable chemistry, thermoset polyurethanes can be custom formulated to meet specific compression set requirements. For example, this unique material can display high or low compression sets without sacrificing other key physical properties. This is often a major restriction for other traditional materials, such as rubbers and thermoplastics. Moreover, thermoset polyurethanes can typically display improved compression sets for extended performance and wear. If you are curious in learning more about what thermoset polyurethanes have to offer your product design when compared to plastics, rubbers, and metals - download our white paper here.
How to use Compression Set in your Design
When considering compression set in your design, it is important to understand your product's function and overall performance requirements. Take seals and gaskets as an example. The intended function of these types of products is the use of compressive forces to create tight closures. If a material with a high compression set is employed, the material's ability to seal properly would remain permanently deformed over time - creating undesirable leaks or significant damage. Applications, such as leak tests, automotive, and fitness & recreation to name a few, frequently rely on low compression materials for extended performance. To avoid any catastrophic failures, thermoset polyurethanes should be considered for their customizable properties and design freedom to meet exact compression set requirements.
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