After finding the appropriate type of rubber—such as neoprene compound—for an application, one of the most important specifications to consider is durometer. Neoprene and other elastomers are available in a number of different combinations to suit any and most uses: such as thin or thick sheets of neoprene, a sponge neoprene roll, 100%-neoprene padding, or a neoprene blend sheet. Using a durometer will allow you to determine whether you need hard neoprene or soft neoprene. Durometer is one variable present in all of different forms of the product, and it is needed to determine the density of neoprene as well as of other elastomers. Neoprene durometer is an effective way to measure the flexibility and the pliability of the material. This synthetic rubber’s array of physical and chemical properties is so valuable most neoprene manufacturers opt to produce this all-purpose elastomer in multiple forms. In this article, we’ll answer the following questions:

• What is a durometer rating of neoprene?
• What is 40-durometer neoprene rubber?
• What durometer is neoprene?
• Are there different grades of neoprene?

What Is a Durometer Rating of Neoprene?

The durometer rating of neoprene is the quantitative measurement of neoprene material’s hardness. To gain a deeper understanding of this concept, let’s ask: What exactly is durometer? Neoprene—and all rubbers, in general—have their hardness measured. Neoprene hardness, according to Wikipedia, is “a material’s resistance to permanent indentation.” In the 1920s, a hardness-measuring device was invented by Albert F. Shore. Confusingly enough, the device was named after the very unit of measurement the device was designed to measure. What this amounts to is a linguistic conundrum that persists to this day: A durometer measures a material’s durometer. Nonetheless, the durometer is a remarkable tool, and it has helped us categorize materials like neoprene rubber into different classes of hardness.

How does a durometer work? The device drives an indenter through a given material at a constant and steady rate. The indenter is then removed, and the depth of the indentation is measured. The depth of the indentation is what determines the number that the device displays—from 0 to 100. If the indenter fully penetrates the material, the durometer will read “0” (which indicates a very soft material). if the indenter does not penetrate the material at all, the durometer will read “100” (indicating a hard material). If one is measuring the durometer of neoprene material, it is imperative that the neoprene block being tested is at least 1/4” neoprene (in terms of thickness) and that there is a hard subsurface under the subject. Testing 1/4" neoprene or thicker (such as 3/8” neoprene, 3/4” neoprene, or 2” neoprene) allows for proper results. Thin neoprene that fails this requirement lacks the sufficient matter for accurate testing.

What Is 40-Durometer Neoprene Rubber?

In short, 40-durometer neoprene rubber is relatively soft. But, notice that when we use terms like hard and soft, we implicitly invoke comparisons. Thus, when we examine a material’s hardness without a reference, the resulting measurement gives us little understanding of how hard the material actually is. For example, hard neoprene would have a durometer of approximately 65 to 75, while soft neoprene would measure at about 45 durometer. There are softer and harder products in the market though, so viewing this matter through a more holistic scope benefits our understanding of neoprene durometer. The density of neoprene and any other elastomer determines which scale the material belongs to. Softer materials, like a bicycle gel-seat or a household sponge, are measured with the Shore 00 scale. Denser materials, like a rubber sheets or skateboard wheels, are measured with the Shore A scale. The Shore D scale is used for even harder materials, such as plastics.

What Durometer Is Neoprene?

It is important to know how to read durometer in relation to the durometer scale. As mentioned above, higher durometers generally apply to harder materials (e.g., 80-durometer neoprene is harder than 70-durometer neoprene). However, if hardness is compared across two different scales (e.g., Shore 00 versus Shore A), you might find yourself confused. By way of example, a sponge neoprene roll might have a durometer of 60 on the Shore 00 scale, while soft neoprene that’s nonetheless solid might have a durometer of 45 on the Shore A scale. The sponge rubber is evidently less dense and less hard than the sheet neoprene; but, being measured by different scales makes it seem as if you’re dealing with two very different materials—even when they are very similar to each other. The Shore scale groups and measures materials relative to other materials in the same scale. The neoprene durometer-metric would then always be followed with an indication of what type of Shore is being used: for example, “60-Durometer Neoprene Shore A.” Again, if you do take the measurement, make sure that you do use 1/4” neoprene or thicker to test.

Are There Different Grades of Neoprene?

Simply put, there are different grades of neoprene, but the demarcations we assign to neoprene rubber are most-often based on durometer, or hardness. One might consider sponge neoprene and solid neoprene to be different grades of neoprene, but this way of distinction isn’t the norm. (We’re better off considering neoprene foam and solid neoprene as different types of neoprene.)

It’s important to pay attention to the specifications of a neoprene rubber sheet, like neoprene compression-set, neoprene temperature-range, and neoprene durometer. Neoprene, in particular, is available in a host of unique combinations of physical and chemical traits, and it is crucial to understand how these differing traits specialize in different applications. Soft neoprene is going to be used for applications in which a pliable neoprene material is needed, whereas hard neoprene will be used for applications in which a rigid, sturdy material is necessary. One must also remember that the density of neoprene will determine the type of Shore by which neoprene durometer is measured. There are three different scales—each will produce a different reading for the same product. Neoprene durometer doesn’t seem so complicated at first, it can get confusing quickly without the right technical expertise. We hope this article gives you more insight into the concept of not just neoprene durometer, but durometer in general.