Category Archives: Prototypes

Modulus of Elasticity for Rubber Sealing Compounds – The Tensometer

Tensile Strength | Ultimate Elongation | Modulus of Elasticity

Rubber Compound Data sheets usually display a number of physical properties as recorded from standard test methods. Among the most common are three measured on the Tensometer:

  1. Tensile Strength (at break)
  2. Ultimate Elongation
  3. Modulus of Elasticity

The Test

Picture of TensometerThe Tensometer stretches a specimen, or dumbbell, cut from a sheet of rubber, until it breaks. During the test, the force required and length of the gauged section are measured continuously. These measurements are used to calculate the various results, which considers the actual dimensions of the test specimen.

While Tensile Strength and Ultimate Elongation are pretty well understood by most, Modulus is not as well understood. Unlike the other two, the Modulus values are not usually reported at break, but rather at various elongation percentages as recorded during the test. Modulus is reported in pounds per square inch (psi) or Megapascals (MPa) at a given elongation percentage as below:

Modulus @ 100% Elongation: 610 psi 4.2 MPa

The Results

You might ask, “What does knowing the Modulus do for me?” While Modulus and Durometer are somewhat related, there can be a pretty large variance in modulus values between two compounds of the same durometer. In an application that requires a rubber seal to be stretched into place, a low modulus compound might be considered to make assembly easier. On the other hand, a firmer compound would be preferable in an application where stretchiness is not desirable. In this case, a high modulus compound would be superior. Higher modulus is also a good indicator of a compound’s ability to resist extrusion in high pressure sealing applications.

This article is not intended to explain at length, the technical aspects of tensometer testing and resultant properties.  To see an actual test performed on an 80 Durometer EPDM, look below:


The original article can be found on Precision Associates website.

Gallagher Fluid Seals is a preferred distributor for Precision Associates. For more information, or if you have a custom engineering question, please contact our Engineering Department.

VIDEO: Extruded Profiles & Parts

Gallagher has long been a top Parker Distributor.  The Parker TechSeal Division designs and manufactures custom elastomer products using extrusion, precision cutting, and fabricating technologies. The extruded rubber products can be supplied in multiple forms such as cut parts, long lengths, bulk footage, or fabricated gaskets and seals. The video below provides an insight into TechSeal’s day to day operation including manufacturing, material development, and design assistance.

Continue reading VIDEO: Extruded Profiles & Parts

VIDEO: Freudenberg Xpress Rapid Production Cell

Customers often come to Gallagher Fluid Seals with the need for very short lead times for a seal.

Whether it is a piece of equipment that is down or a need for quick prototypes, Gallagher can assist you in developing the required seal profile and material for your application. We can have parts in your hands within 24 hours if necessary.

Our work is made possibly by the help of valued partners such as Freudenberg Sealing Technologies.

Watch the video above to learn more about the capabilities of Freudenberg Xpress cell.

Continue reading VIDEO: Freudenberg Xpress Rapid Production Cell