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What is EPDM Rubber?

Wednesday, November 11, 2020

Ethylene propylene diene monomer (otherwise known as EPDM) is a high-density synthetic rubber that is made up of ethylene, propylene, and diene monomers. 

The long-term lifespan of EPDM products allows for fewer replacement parts, saving money in the long run.

First and foremost, it is extremely durable. Considered to be the premier weather-resistant synthetic elastomer, EPDM rubber has excellent heat, ozone, UV, aging, and weathering resistance. It also exhibits excellent electrical insulation, good compression set and low-temperature properties. EPDM rubber is resistant to a wide range of fluids including water, ethylene glycol (anti-freeze) and offers good resistance to most water-based chemicals and vegetable-based hydraulic fluids. EPDM is also resistant to many mild acids, liquid fertilizers and synthetic brake fluids.

Where is EPDM typically used?
EPDM rubber is one of the most commonly used and fastest growing synthetic rubbers having both general-purpose and specialty applications. The largest market for EPDMs is the automotive industry. This is mainly due to its flexibility, high heat and weather resistance, and vibration absorbing properties. 
Typical automotive industry applications include:
  • Radiator and heater hoses 
  • Window and door seals
  • Wire and cable connectors
  • Weather stripping
  • Braking system
  • Rub strips
Are there any limitations to EPDM? 
EPDM is not recommended for uses requiring resistance to oil, gasoline, and hydrocarbons. It displays limited compression set resistance and offers poor adhesion to fabrics and metals.
What are the physical characteristics of EPDM?
As you can see, when describing an elastomer (such as EPDM) you will often hear words such as durometer, tensile strength, elongation, compression set, and (along with those) you will hear references to something called “ASTM D2000.” Unless your daily life involves elastomers, you’re probably not going to be familiar with these terms. If you want to understand more about EPDM, then you have come to the right place! 
What is the ASTM D2000 Specification?
In order to provide guidance in the selection of rubber materials, the Society of Automotive Engineers (SAE) and the American Society for Testing and Materials (ASTM) established ASTM D2000. The overwhelming majority of specifications for rubber compounds are based on ASTM D2000, “Standard Classification for Rubber Products in Automotive Application.” Don’t let the title fool you, though. This standard applies to just about all industries (including aerospace, medical, and construction).
Durometer, also known as Shore durometer, is a standardized way to measure the hardness of materials like rubber and plastics. The scale ranges from 0 to 100, and the higher the number, the harder the compound. “70 Shore A” is the standard for EPDM which means that “60 Shore A” is softer and “90 Shore A” is very hard. To be more specific, the ASTM D2000 Specification for EPDM is 70 (+/- 5). However, the full range available for EPDM is anywhere from 30 Shore A to 90 Shore A.
Tensile Strength is the resistance of a material to stretch. Typically expressed as pounds per inch at the breaking point. The ASTM D2000 Specification for EPDM is 2031 psi. The typical range available for EPDM is between 500-2500 psi.
Elongation is the maximum a product can stretch before breaking. It is expressed as a percentage reflecting the size of the product when it breaks vs. its starting point. Typical elongation for EPDM is 600%. While this might be a very important aspect, depending on the end use, there is not a specific ASTM D2000 requirement for elongation.
Compression Set is the amount of permanent deformation that occurs when a material is compressed to a specific deformation, for a specified time, at a specific temperature. The ASTM D2000 requirements for EPDM (using a compression set of 22 hours at 125˚ C) call for a permanent set of 25%. This represents the percentage of the original compression (25%) that is not recovered.
Where can I buy a custom manufactured EPDM product?
The coronavirus pandemic has disrupted the demand and supply chain of many products, including EPDM. This has left many struggling to find a domestic supplier. According to a recent publication from Thomasnet, “One in five companies had production facilities in China, the country first affected in the pandemic.” The same report went on to say that in May/June of 2020, the number of North American manufacturers looking to source domestically skyrocketed to a staggering 69%. 
As a custom rubber manufacturer in the U.S. since 1923, Alliance is equipped to formulate custom EPDM compounds specifically designed for your application. 
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