90A Hardness: Your Guide To Durometer Ratings

Hey guys! Ever wondered what those numbers and letters mean when you're looking at wheels, bushings, or other polyurethane parts? Let's dive into the world of durometer ratings, specifically focusing on 90A hardness. This is your ultimate guide to understanding what 90A hardness means, how it's measured, and why it matters for various applications. Whether you're a skater, engineer, or just curious, this article will break it down in a way that's easy to understand. So, buckle up and let's get started!

What is Durometer?

Before we zoom in on 90A hardness, it's essential to understand what durometer is in general. Durometer is the measure of a material's resistance to indentation. In simpler terms, it tells you how hard or soft a material is. The durometer scale was invented by Albert Ferdinand Shore in the 1920s, and it has since become an industry standard for measuring the hardness of polymers, elastomers, and rubbers. This measurement is crucial because it helps engineers and manufacturers select the right materials for specific applications. A material's hardness directly impacts its performance, durability, and overall suitability for its intended use. Without a standardized way to measure hardness, it would be incredibly difficult to ensure consistency and quality across different products and industries.

The durometer scale isn't just one single scale; there are several, each designed for different types of materials. The most common scales are the Shore A and Shore D scales. The Shore A scale is used for softer, more flexible materials like rubber and soft plastics, while the Shore D scale is used for harder materials like hard plastics and some types of hard rubber. When you see a durometer rating, it will usually be followed by either an 'A' or a 'D' to indicate which scale was used. Other scales exist, such as Shore OO, which is used for very soft materials like gels. Understanding which scale is being used is crucial because a 90A hardness rating is very different from a 90D rating. The numerical value represents the material's resistance to indentation, with higher numbers indicating greater hardness. By using the appropriate scale and understanding the numerical ratings, manufacturers can ensure they are using materials that meet the specific requirements of their products, enhancing both performance and longevity.

Breaking Down 90A Hardness

Now, let's specifically talk about 90A hardness. When you see a material rated as 90A, it means that, on the Shore A scale, it has a relatively high level of hardness. Materials with a 90A durometer rating are firm but still offer some flexibility and resilience. This makes them suitable for a wide range of applications where a balance between hardness and flexibility is required. Think of it as being harder than a typical rubber band but not as rigid as a hard plastic like a Lego brick. The 90A rating indicates that the material will resist indentation under moderate pressure but will still be able to deform and recover to some extent. This balance is crucial in applications where the material needs to withstand wear and tear while also providing some level of cushioning or shock absorption. It's a sweet spot that combines durability with a degree of pliability.

To put 90A hardness into perspective, let's compare it to other common durometer ratings on the Shore A scale. Materials with lower durometer ratings, such as 60A or 70A, are much softer and more flexible. These are commonly used in applications like soft rubber seals or flexible gaskets where a high degree of pliability is needed. On the other end of the spectrum, materials with higher durometer ratings, such as 95A or higher, are much harder and more rigid. These are often found in applications like hard plastic rollers or durable wheels where minimal deformation is desired. A 90A rating sits comfortably in the middle, offering a balance that makes it versatile for various uses. For example, skateboard wheels with a 90A durometer provide a good grip while still allowing for smooth rolling on various surfaces. This balance is what makes 90A such a popular choice in many different industries.

Applications of 90A Hardness

90A hardness is a versatile rating that finds its way into numerous applications across various industries. Its unique balance of durability and flexibility makes it a go-to choice for components that need to withstand wear and tear while still providing some level of cushioning or responsiveness. Let's explore some of the most common and significant applications where 90A hardness plays a crucial role.

Skateboarding Wheels

One of the most well-known applications of 90A hardness is in skateboard wheels. Skateboard wheels need to be hard enough to provide good speed and roll efficiently, but also soft enough to offer some grip and absorb vibrations. Wheels with a 90A durometer rating strike an excellent balance, making them popular among street and park skaters. They provide a smooth ride on a variety of surfaces, from smooth concrete to slightly rough asphalt. The hardness allows for controlled slides and tricks, while the slight give ensures that the skater doesn't lose control on uneven surfaces. This makes 90A wheels a versatile choice for skaters who need a reliable wheel that can perform well in different conditions. The 90A hardness ensures that the wheels wear well over time, providing a long-lasting and consistent performance.

Bushings

Bushings, small components used in various mechanical systems, frequently utilize 90A hardness polyurethane. In skateboarding, bushings are crucial for the turning mechanism of the trucks. A 90A bushing offers a medium level of resistance, allowing for responsive and controlled turning. This hardness provides stability at higher speeds while still allowing for tight turns when needed. Beyond skateboarding, 90A bushings are used in automotive suspensions, industrial machinery, and other applications where controlled movement and vibration damping are required. The 90A hardness ensures that the bushings can withstand constant stress and compression without deforming or breaking down, providing long-term reliability and performance.

Industrial Rollers

In industrial settings, rollers with a 90A hardness rating are used in various material handling and conveyor systems. These rollers need to be durable enough to withstand the constant friction and pressure of moving heavy loads, but also offer some flexibility to prevent damage to the materials being conveyed. A 90A durometer provides the necessary hardness for smooth and efficient operation while also minimizing the risk of marking or damaging sensitive materials. These rollers are commonly used in industries such as packaging, printing, and manufacturing, where reliable and consistent material handling is essential. The 90A hardness ensures that the rollers can maintain their shape and performance over extended periods, reducing downtime and maintenance costs.

Seals and Gaskets

Seals and gaskets made from 90A hardness materials are used in applications where a tight and reliable seal is required. This hardness provides a good balance between flexibility and compression resistance, allowing the seal to conform to irregular surfaces while still maintaining its integrity under pressure. These seals are commonly used in hydraulic systems, pneumatic systems, and other applications where preventing leaks is critical. The 90A hardness ensures that the seals can withstand high pressures and temperatures without deforming or failing, providing a long-lasting and effective sealing solution.

Advantages and Disadvantages of 90A Hardness

Like any material characteristic, 90A hardness has its own set of advantages and disadvantages. Understanding these can help you determine if 90A is the right choice for your specific application.

Advantages

• Durability: Materials with 90A hardness are generally quite durable and resistant to wear and tear. This makes them suitable for applications where the material will be subjected to constant friction, pressure, or abrasion.
• Good Balance of Flexibility and Rigidity: 90A offers a sweet spot between flexibility and rigidity, providing some cushioning and shock absorption while still maintaining a firm and stable structure.
• Versatility: The balance of properties makes 90A hardness suitable for a wide range of applications across different industries.
• Resistance to Deformation: Materials with 90A hardness are less likely to deform under load compared to softer materials, ensuring consistent performance over time.

Disadvantages

• Less Grip Compared to Softer Materials: While 90A offers good grip, it may not be as grippy as softer materials like 70A or 80A. This can be a disadvantage in applications where maximum grip is required.
• Can be Too Hard for Some Applications: In applications where a high degree of flexibility or cushioning is needed, 90A hardness may be too stiff and uncomfortable.
• May Transmit More Vibration: Compared to softer materials, 90A may transmit more vibration, which can be a concern in applications where vibration damping is important.
• Not Ideal for Very Rough Surfaces: While versatile, 90A hardness may not perform optimally on extremely rough or uneven surfaces, as it may not provide enough cushioning or grip.

How to Choose the Right Durometer

Choosing the right durometer for your application involves careful consideration of several factors. Here are some key steps to guide you through the selection process:

1. Identify the Application: Start by clearly defining the specific application for the material. What will it be used for? What are the primary functions it needs to perform? Understanding the application is the most critical step in selecting the appropriate durometer.
2. Consider the Environmental Conditions: Think about the environmental conditions the material will be exposed to. Will it be subjected to extreme temperatures, chemicals, or UV radiation? These factors can significantly impact the performance and longevity of the material.
3. Determine the Required Balance of Properties: Decide what balance of properties is needed. Do you need high flexibility, high durability, good grip, or excellent vibration damping? Prioritize the properties that are most important for your application.
4. Consult Material Data Sheets: Review the material data sheets for different durometer ratings. These sheets provide detailed information about the material's properties, including hardness, tensile strength, elongation, and chemical resistance.
5. Test Samples: If possible, obtain samples of materials with different durometer ratings and test them in your application. This is the best way to determine which durometer provides the optimal performance.
6. Seek Expert Advice: If you're unsure about which durometer to choose, consult with a materials engineer or supplier. They can provide valuable insights and recommendations based on their experience.

By following these steps, you can make an informed decision and select the durometer that will provide the best performance and longevity for your specific application. Remember, choosing the right durometer is crucial for ensuring the success and reliability of your project.

Conclusion

So there you have it! 90A hardness demystified. We've explored what durometer is, what 90A means, its applications, advantages, and disadvantages. Hopefully, this guide has given you a solid understanding of 90A hardness and how it compares to other durometer ratings. Whether you're choosing skateboard wheels, industrial rollers, or seals, understanding durometer is crucial for making the right decision. Now you're armed with the knowledge to choose the perfect material for your needs. Keep this information handy, and you'll be making informed decisions in no time. Happy material hunting!