After finding the appropriate type of rubber 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, sponge neoprene, 100% neoprene or blended neoprene. 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 other elastomers. Neoprene durometer is an effective way to measure the flexibility and the pliability of the rubber. This rubber’s array of physical and chemical properties is so valuable that the all-purpose elastomer cannot be limited to just one form!

So what exactly is durometer? Neoprene—and all rubbers, in general—have to be measured for their hardness, which is “a material’s resistance to permanent indentation” according to the Wikipedia definition (http://en.wikipedia.org/wiki/Shore_durometer). In the 1920s, the device was invented by Albert F. Shore; confusingly enough, the device which was named after the very unit of measurement for which it is used to determine. So, a durometer will measure a material’s durometer

The device drives an indenter through a given material at a constant and steady rate. The indentor is then removed, and the depth of the indentation is measured. The depth of that penetration is what will determine the number that is on the reading, from 0 to 100. If the indenter fully penetrates the material, the durometer is 0 (which would be a very soft material); if the indenter does not penetrate at all, the durometer is 100 (a very hard material). It is imperative that the material used to test be at least 1/4”neoprene and have a hard subsurface under the product. Testing 1/4" neoprene or thicker allows for proper results. Thinner material will not have enough “meat” for the test.

When terms like hard or soft are used, we are using comparative terms. On their own they are really useless. 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 as well, so having a grip on the scale is important. The durometer measurement must be viewed in context with the durometer scale that is appropriate to the material. The density of neoprene and any other elastomer determines which scale the material belongs to. Softer materials, like a bicycle gel seat or 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 any harder materials like plastics.

It is important to understand how to read durometer in relation to the durometer scale. As mentioned above, higher durometers generally apply to harder materials (e.g. the 65 durometer of hard neoprene is harder than the 45 durometer of soft neoprene.). However, if hardness is compared across two different scales, one might find themselves scratching their head in confusion. Case in point, sponge neoprene can have a durometer of 60 in the Shore 00 scale, while soft neoprene has a durometer of 45 in Shore A scale. The sponge rubber is clearly less dense and less hard than the sheet neoprene, but being measured by different scales would make it seem as if you were dealing with two very different materials, even when they are very similar to each other. The Shore scale groups and measures materials that are relative to other materials in the same scale. The neoprene durometer metric would then always be followed with a shore like, 70 Durometer Neoprene Shore A. If you do take the measurement, make sure that you do use 1/4”Neoprene or thicker to test.

It’s important to pay attention to the specifications of rubber like compression set, operable temperature range and durometer. Neoprene, in particular, is available in a host of unique combinations of physical and chemical traits, and it is crucial to understand how they fit in with a certain application. Soft neoprene is going to be used for applications in which a pliable material is needed, and 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 which scale is necessary to take the measurement. There are three different scales and they will all produce a different reading for the same product. All these complications are exactly why a highly-technological piece of equipment is needed!