Low Hardness Urethanes — Harkness Industries’ Softer Side

When looking for ultra-low hardness in urethanes, it’s tough to find materials that perform without “sweating.” Since 2003, Harkness Industries has used a unique process to produce more than 55,000 urethane sheets, tubes and rods at hardnesses from 10A to 50A.

What’s does 10A to 50A indicate? And what is wrong with “sweating?”

Urethane hardness is measured on two different scales —the “A” scale and the “D” scale. The “A” scale goes from 0 to 95 and the “D” scale goes from 45 to 85. While there are some plastics that are harder than 85D, urethanes max out in hardness at 80 to 85D.

When low hardness urethanes are formulated to a hardness below 60A, the most common approach is to add a plasticizer and what’s known as low durameter urethanes are created. When a plasticizer is added to a urethane it causes the hardness to drop. The more you add, the lower the hardness becomes. A plasticizer will not react with the urethane, it is basically filler. Adding more plasticizer makes it more difficult to keep the plasticizer from “bleeding out.” Once you get below 30A hardness, the plasticizer comes to the surface like sweat. The urethane begins to increase in hardness because it is losing the chemical that made it softer in the first place.

Unable to solve the “sweating” or “bleeding out” issue, many urethane parts suppliers will not go below a hardness of 30A. Harkness does not back away from this challenge. We produce 55,000 urethane sheets, tubes and rods at hardnesses from 10A to 50A for the last 10 years.

Low durometer urethane elastomers find many industrial uses including roll covers, grommets, bushings and vibration isolators.

This is what Harkness offers to meet this unique material need

  • 10A to 50A precision cast 48” x 48” sheets from thicknesses of 1/32” up to 3” in standard natural or black with custom colors upon request.
  • Rod sizes are available from ¼” to 10” diameter in lengths of 36” to 48”
  • A huge variety of 36” and 48” long tubes by mixing and matching inside diameter (ID) and outside diameter (OD) beginning with diameters of ¼” up to 10”.

Harkness strives to meet any material request. Our variety of different sized IDs and ODs is unmatched in the industry. If we don’t have it, we’ll go buy the ID/OD combination you need.

If you are in search of this type of personal customer service, all you need to do is call 203-272-3219 and start building a relationship.

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