Introduction
For any Façade or Building - Sunlight and weather elements can drastically reduce the life span of most general purpose sealing elastomers like Neoprene. The natural ability of EPDM (Ethylene Propylene Diene Monomer) to withstand ambient harsh weather, water and temperature extremes makes it an outstanding choice for use in Architectural Profiles, Glazing Gaskets, Weather Seals, Expansion Joints, Waterproofing Membranes and other exterior building product applications.
What is EPDM?
Ethylene-Propylene Diene Monomer (EPDM) is an Elastomer.
Elastomers are made from raw rubbers with various additives. The Elastomers have an open, crosslinked structure. These elastomers are elastic, and after stretching or compressing they reconfigure to their original shape. The crosslinking itself is irreversible; in other words, the shape of an elastomer part that has been crosslinked cannot be permanently changed.
For the Elastomer - EPDM is a primary ingredient in the compound that is used to create these Gaskets, Profiles or Membranes. Other ingredients include Carbon Black, Oil and vulcanization systems. However, the unique properties of the finished product are generated by the EPDM. The rubber compound is produced in large mixers, shaped into a profile or a molded article through an Extruder, then vulcanized by heating the shaped compound at 240-260 degrees Celsius in a Microwave Oven, resulting in the finished rubber product - GASKET.
Key characteristics of EPDM Rubber
- Once a rubber compound has been vulcanized the material is irreversible. The material shape cannot be changed by heating because it won't melt, but it will burn.
- To give a finished rubber product elasticity as well as tensile strength, carbon black is added to the compound. As a result, normally, EPDM rubbers can only be produced in black.
- Thermal ageing, with superior heat ageing properties and ability to withstand varying climatic changes, thus maintaining excellent deflection recovery performance.
- Excellent resistance to UV and Ozone attack, thus resulting in no migration and staining.
Mechanical Properties of EPDM - Overview
The basic characteristic of EPDM is its excellent Durability. There is absolutely no necessity to add any anti-aging agents in the elastomer.
Regarding its other mechanical properties, EPDM has a very good tear strength and elongation at break characteristics., The tear propagation resistance, is also average to good.
With regard to Compression Set, EPDM has very good values for compounds cured with Peroxide, whereas Sulfur-crosslinked compounds are only average in this category.
Thermal Properties of EPDM - Overview
You can notice some variations between the thermal properties of the differently crosslinked EPDM compounds. The Peroxide-crosslinked EPDM materials have better temperature resistance than sulfur-crosslinked compounds.
Peroxide-crosslinked EPDM blends are heat resistant, under continuous heat, to about 130° C, although this can be increased to 170° C for short periods. In general, the heat resistance of peroxide-crosslinked EPDM is roughly comparable to that of HNBR (hydrogenated acrylonitrile-butadiene rubber).
In the case of Sulfur-crosslinked compounds, it is recommended that the temperature does not exceed 100° C for continuous exposure. However, this temperature resistance can be increased to about 1300 C by the vulcanization process.
The cold temperature resistance of EPDM is excellent and normally highly dependent on the Ethylene content of the EPDM base mix. Cold temperature resistance is observed to be better for a lower Ethylene content (40 to 50 percentage by mass of components). However, low Ethylene content generally leads to inferior dynamic properties of EPDM. On the other hand, high Ethylene content (60 to 70 percentage by mass of components) results in poor cold behavior of the material. Interestingly, this does not apply to the compression set, which increases with increased ethylene content, even in cold weather.
Chemical Properties of EPDM - Overview
EPDM shows its very good resistance to polar chemicals, such as water, wastewater, alkalis, alcohol and glycols, and this has opened up many potential applications. In addition, acids and various organic and inorganic bases are not a problem for EPDM.
It also shows very good resistance to hot water and water vapor up to 130° C. With a suitable compound formulation, this may even be increased to 150° C.
Furthermore, EPDM has very good insulation properties due to its very high level of electrical resistance.
However, the material EPDM shows weaknesses in contact with mineral oils, fuels and fats and here EPDM is almost unusable. There are also problems with aliphatic, chlorinated and aromatic hydrocarbons.
In a nutshell, EPDM Rubber demonstrates excellent environment and thermal stability, with superior heat aging properties and resistance to abrasion and flex fatigue, whilst retaining flexibility at extremely low temperatures. It is resistant to a wide range of aqueous and oil based fluids, UV and ozone attack without degradation and is non-migratory. The EPDM Rubbers do not require reinforcing fillers or extenders to achieve their high level of mechanical properties. All the above properties make EPDM a superior choice than other conventional Elastomers like Neoprene etc..
Why EPDM and the Construction Industry are a good fit?
EPDM rubber products provide superior UV & Ozone resistance; long life and elasticity. As a result, EPDM is a highly valued material in the Building Construction Industry (primarily – Aluminium Fabrication Segment, Curtain-wall Industry, uPVC Doors & Windows Segment and Expansion Joint Segment), which represents 40% - 45% of world wide EPDM usage. Within this category, Curtainwalling systems is the largest application (40%). The Roads & Bridges segment of the Building Construction Industry use EPDM Expansions Joints primarily because of it’s intrinsic nature of being Ozone Resistant.