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MPC  Polyurethane Knowledge Center

Rubber vs Polyurethane Seals: Which Material Should You Choose?

Rubber and polyurethane are two types of materials that are commonly employed in leak test seals. While there are many formulations to choose from within these two polymers, each material has its unique physical properties that can improve or weaken the performance of your leak test. To help streamline your material decisions, we will discuss these two commonly employed materials and explore which ones may be best for your application.


What is Rubber?

Rubbers are a family of polymeric materials based on the chemistry of natural rubber latex. While there are many synthetic rubbers on the market, they share a basic chemical composition with natural rubbers. While rubber is a cost-effective solution for many applications, its physical properties often prevent superior performance, especially in extreme environments. 

What is Polyurethane?

Polyurethanes are formed through the chemical reaction between a polyol and diisocyanate. Despite having a complex chemical structure, polyurethanes like thermosets can be custom formulated to meet exact design and performance requirements. As a result, polyurethanes can virtually be found anywhere in applications like medical devices, military & defense, and packaging to name a few. 

Differences Between Rubber & Polyurethane

While rubber and polyurethanes may have a few similarities, there are many distinct differences between the two. As an example, the table below breaks down these variations to help discern between the two sought-after materials:

Benefits of Rubbers Benefits of Polyurethane
Different  grades are available in solid form Solids or foams available at any hardness without sacrificing performance
High elasticity and compression set Customizable  properties to achieve exact performance requirements
Some rubbers are able to withstand temperatures up to 580°F  Highly flexible in various environments, chemicals, & temperatures
Rubber is biodegradable & can breakdown when not in use Longer life, especially in outdoor or extreme environments
Often more cost effective for standard materials & shapes Flexibility to be custom molded into any shape or complex geometry

Which Material Should you choose?

Rubber and polyurethane seals are commonly used for their material selection and physical properties. Depending on its environmental conditions and overall function, one material is usually a better option over the other. For example, leak tests are often an excellent application for polyurethane seals as helium is typically employed during testing. Unlike rubber, polyurethanes can exhibit superior abrasion resistance, tensile strength, and tolerances to greases, oils, oxygen, and ozone. In addition, polyurethanes like thermosets can offer product engineers an endless range of customizable formulations and manufacturing capabilities to achieve complex geometries and better performance for extended wear. Because rubber is biodegradable, it tends to rot and degrade over time with exposure to certain elements - leading to potentially inaccurate test results and frequent seal replacements. For this reason, polyurethanes are often preferred for applications that require very specific physical properties for improved performance. 

If you find custom leak test seals are a key requirement for improved performance, this can easily be tailored by your thermoset polyurethane manufacturer. For material assistance, complete our design tool here, or click the button below to start your custom polyurethane seal today.

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