Hard rubber and high durometer rubber display many of the same characteristics. You could be forgiven for thinking that the terms are interchangeable. While it is true that they share very similar features, there is a specific technical distinction that separates tough rubber from the term “Shore A” rubber. The purpose of this writing is to inform you of the key features that shore a rubber determine specific rubber hardness with the definition of durometer.
First, let us deal with the term “durometer”. Specifically, durometer is the material’s ability to resist permanent physical indentation. It is a unit of measurement that is commonly used in the rubber industry to determine this type of physical resistance. One of the most common types of durometer ratings of a specific rubber is the Shore A classification. The exact Shore A rubber ratings will vary from rubber to rubber, but they generally come from 20 to 90. Generally speaking, the lower the durometer rating, the more flexible and less resistant to permanent indentation a rubber will be. The converse of this is true as the rating goes up in scale.
Essentially, durometer is only a term used to measure the exact degree to how hard and tough rubber materials can be. When people talk about a hard rubber, they are more likely generalizing about the rubber’s durability. They are not specifically referring to the exact level of how durable the product is. Instead, all they know is that the rubber is tough and durable. In such a case, they are more than likely referring to a high durometer rubber.
Hardness is more of a general umbrella term that encompasses a variety of different components. In addition to measuring the resistance against indentation, or durometer, it also refers to the measure of how resilient an elastomer is to fracture or deformation from sharp objects. It can also take into account the elasticity of a specific hard rubber product. Elasticity determines the relative rebound an object would retain after having an object dropped on it. In short, rubber hardness is not only about indentation, but also refers to how difficult the material is to cut and how it reacts to other factors. Hard rubber, while generally of a higher durometer and more difficult to compress, could at times be less difficult to cut.
With this in mind, asking about the durometer and elasticity of a tough rubber material would be much more informative then asking if the rubber is simply “hard”. Similarly, high and low durometer rubber ratings should not be used interchangeably with a material’s resistance to scratches, abrasion, or wear and should not be used alone for material design specifications. There is a strong correlation between rubber hardness and Shore A rubber durometer, but they are not the same exact thing. It is recommended to try to not refer to them as the same concept.
With these distinctions in mind, it is important to note the similarities. Hard rubber and high durometer rubber share enough features that can lead to people confusing them for being interchangeable. They are both resistant to flexure, both are resilient to change when an outside force is applied, and both oppose deformation of their physical structure. However, as mentioned earlier, a high durometer rubber and a hard rubber use different measurements to define and determine the range between high and low durometer and hard and soft.
Next time you are in the market for a durable and tough rubber material, go beyond asking for a simple hard rubber. Instead, look for information regarding the elastomer’s durometer rating, its level of elasticity, how easy it is to cut, and other details along those lines. By asking for those specific details, you can get the best hard rubber and high durometer rubber for your intended application.