Selecting the correct polyurethane durometer for your application can make the difference between a successful seal and a crumbly coupling. In today’s article, we will guide you through the effect that durometer has on other polyurethane properties, how it’s measured, and how to choose the right one for your specific needs- with a helpful tool at the end.
The Significance of Polyurethane Durometer
Polyurethane is a versatile material used in various industries, from automotive to medical devices. The hardness of polyurethane can significantly affect its performance characteristics, such as flexibility, durability, and resistance to wear and tear.
Applications of Different Polyurethane Durometers
- Extra Soft Polyurethane (Shore OO 25-40): Best for low-pressure applications to cushion impacts or create an airtight seal.
- Soft Polyurethane (Shore A 20-40): Ideal for applications requiring high flexibility and cushioning, such as seals and gaskets.
- Medium Polyurethane (Shore A 50-70): Suitable for parts that need a balance between flexibility and durability, such as wheels and rollers.
- Hard Polyurethane (Shore A 80-95 or Shore D 30-50): Used in applications requiring high wear resistance and load-bearing capacity, such as bushings and industrial components.
The Shore Hardness Scale Explained
The Shore Hardness Scale is a standardized method to measure the hardness of materials, particularly elastomers and polymers. Named after its creator, Albert F. Shore, this scale quantifies the resistance of a material to indentation with a numerical value that represents its hardness. That numeric value is what’s referred to as the durometer of an elastomeric material like polyurethane.
Types of Durometer Scales
There are several hardness scales, each suited for different types of materials. The most commonly used scales for polyurethane products are:
- Shore OO: Measures the softest elastomers.
- Shore A: Measures softer elastomers and flexible plastics. Most polyurethane products fall within this scale.
- Shore D: Measures harder plastics and rigid materials.
The choice between Shore OO, Shore A, and Shore D depends on the specific application and the material’s required mechanical properties. For more info about how the Shore Hardness Scale works, check out our blog post, Understanding The Shore Hardness Scale.
You don’t have to become a polyurethane expert. That’s our job. Speak with our team today to get started on your next polyurethane project.
Factors to Consider
Selecting the right durometer involves considering various factors to ensure the material meets the application’s requirements.
Mechanical Properties
The mechanical properties of polyurethane, such as tensile strength, elongation, and tear resistance, vary with hardness. Higher durometer materials generally offer higher tensile strength and lower elongation, making them suitable for load-bearing applications.
Environmental Conditions
Environmental factors, such as temperature, humidity, and exposure to chemicals, can affect the performance of polyurethane. Softer polyurethanes may become more pliable at high temperatures, while harder polyurethanes may become brittle at low temperatures. Chemical exposure can also degrade the material, so selecting a durometer that can withstand the environmental conditions of the intended application is important for long-term success.
Load-Bearing Requirements
The load-bearing capacity of polyurethane is directly related to its hardness. Harder materials can support greater loads without deforming, making them ideal for applications involving significant mechanical stress.
Application-Specific Requirements
Consider the specific requirements of your application, such as the need for cushioning, impact resistance, or abrasion resistance.
Soft vs. Hard Materials
When comparing soft and hard durometers, there are key differences that will make one choice more suitable than the other for certain applications:
Soft Materials
Due to their low density, soft materials are more flexible and have higher elongation properties than hard materials. This makes them ideal for applications like cushioning and impact resistance. On the chemical side of things, soft materials may be more susceptible to chemical degradation due to their softer nature. These materials can experience better longevity in applications where exposure to chemicals is minimal to avoid material degradation.
Hard Materials
Hard materials offer higher hardness and stiffness, providing excellent wear resistance and load-bearing capacity. These are suitable for applications requiring high wear resistance, such as bushings and industrial components. For the most part, hard materials demonstrate better resistance to harsh chemicals like solvents, oils, and other industrial fluids, making them suitable for applications where chemical exposure is a concern.
Although these properties are generally true for soft and hard materials across the board, our urethane engineers are capable of creating a unique formula that includes a mix of your ideal properties for a given application. Our DrainProtector II is a shining example of a formula that’s an exception to the rule, displaying excellent chemical resistance despite being one of our softest material offerings.
Not all needs fit neatly into one box- and meeting those complex needs is where our team excels. Chat with us to discover what we can do for you.
Practical Examples
To illustrate the importance of choosing the right polyurethane durometer, consider the following examples:
Automotive Bushings
Automotive bushings require a material that can withstand high loads and provide damping to reduce noise and vibration. A medium to high durometer polyurethane (Shore A 70-90) is typically used to balance flexibility and durability, especially with the risk of being exposed to oil and other automotive fluids.
Medical Device Components
Medical devices, such as tubing or seals, require materials that are biocompatible and flexible. Soft polyurethane (Shore A 20-40) is often chosen for these applications to ensure patient comfort and optimal device functionality.
Industrial Rollers
Industrial rollers used in manufacturing processes need to be wear-resistant and capable of handling heavy loads. Hard polyurethane (Shore D 30-50) provides the necessary durability and load-bearing capacity for these applications.
Choosing the right polyurethane durometer is a critical decision that can significantly impact the performance and longevity of your product. By understanding the Shore Hardness Scale, considering the mechanical properties, environmental conditions, load-bearing requirements, and application-specific needs, you can make an informed choice that ensures your product meets its intended function.
The best part is, we have an online tool which helps you narrow down the ideal range for your application. If you already know what your desired application is, you can use our Durometer Reference Calculator to find the ideal starting point for your next project. Of course, every instance is different, but this tool will give you a ballpark estimate that can be further refined with your polyurethane manufacturer.
The PSI team is happy to provide our polyurethane insights for your next project. Talk to us about your application needs today.
