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Silicone-EPDM Blends for Expansion Joint or Insulator Applications
Introduction
Long-chain polymeric molecules are made of up base units, or monomers, and groups. Whilst the underlying chemical structure of these large molecules can be well-understood, the chains can interact and cross-link to form very complex structures, which are difficult to characterize.
This article discusses the benefits and drawbacks of silicone and EPDM and the process of making silicone/EPDM blends.
Silicone Rubber
Silicone exhibits resistance to oxidation, sunlight, ozone and weathering, and shows superior electrical insulation and flexibility at low temperatures. Besides demonstrating superior color stability and low compression set, this synthetic rubber is valued for its usefulness at high or low service temperatures. Although silicone is a costly material compared to EPDM, the service life of silicone seals is much better.
Nevertheless, silicone is not suitable for all applications. The chemical properties of this type of rubber make it unsuitable for applications involving gasoline, oil, solvents, alkalis and acids. The lack of strong resistance to tearing and abrasion is another drawback of silicone.
Despite the availability of a wide choice of outstanding silicone compounds, pure silicone is the appropriate material for applications demanding high tensile strength.
EPDM Rubber
EPDM is also a synthetic rubber, which is used in the production of O-rings, hoses and belts for the mass transit and automotive industries. The material exhibits superior resistance to weathering, aging and zone as well as to alkalis, acids and some solvents. EPDM components maintain flexibility and color stability at low temperatures and resist both steam and water.
However, EPDM is not suitable for applications involving aromatic hydrocarbons and mineral oils, and EPDM compounds are no match for petroleum derivatives. EPDM can be used as a high voltage insulation material, but exhibits electrical conductivity when carbon black is added for improved weathering.
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