EPDM vs. SBR

Attribute	EPDM	SBR
Chemical Name	Ethylene Propylene Diene Monomer	Styrene Butadiene Rubber
Chemical Structure	Terpolymer of ethylene, propylene, and a diene monomer	Copolymer of styrene and butadiene
Hardness	40-90 Shore A	40-90 Shore A
Elongation at Break	300-800%	300-800%
Tensile Strength	7-20 MPa	7-20 MPa
Temperature Range	-50°C to 150°C	-40°C to 100°C
Resistance to Ozone	Excellent	Good
Resistance to Weathering	Excellent	Good
Resistance to Chemicals	Good	Good
Applications	Roofing, automotive seals, electrical insulation	Tires, conveyor belts, gaskets

Introduction

When it comes to synthetic rubber, EPDM (Ethylene Propylene Diene Monomer) and SBR (Styrene Butadiene Rubber) are two popular choices. Both materials have unique attributes that make them suitable for various applications. In this article, we will compare the key characteristics of EPDM and SBR, exploring their strengths and weaknesses.

Chemical Composition

EPDM is a terpolymer made from ethylene, propylene, and a diene monomer. This composition gives EPDM excellent resistance to weathering, ozone, and UV radiation. On the other hand, SBR is a copolymer made from styrene and butadiene. The presence of styrene in SBR enhances its hardness and abrasion resistance, making it suitable for applications that require durability.

Physical Properties

EPDM exhibits superior flexibility and elasticity, allowing it to withstand extreme temperatures ranging from -50°C to 150°C. Its excellent resistance to heat, water, and steam makes it ideal for outdoor applications, such as roofing membranes and automotive weatherstripping. SBR, on the other hand, has a lower temperature range, typically ranging from -40°C to 100°C. Its higher hardness and tensile strength make it suitable for applications like tires, conveyor belts, and gaskets.

Chemical Resistance

EPDM possesses excellent resistance to a wide range of chemicals, including acids, alkalis, and polar solvents. This makes it a popular choice for applications in the chemical industry, such as seals and gaskets. SBR, although not as chemically resistant as EPDM, still offers good resistance to many common chemicals. It is commonly used in applications where exposure to oils, fuels, and hydraulic fluids is expected.

Weathering and Ozone Resistance

EPDM is renowned for its exceptional weathering and ozone resistance. It can withstand prolonged exposure to sunlight, rain, and extreme weather conditions without significant degradation. This makes it an excellent choice for outdoor applications, such as seals, hoses, and roofing materials. SBR, while not as resistant to weathering and ozone as EPDM, still offers satisfactory performance in moderate outdoor conditions.

Tear and Abrasion Resistance

EPDM has good tear resistance, allowing it to withstand mechanical stress and deformation without tearing apart. However, it is not as abrasion-resistant as SBR. SBR's higher hardness and abrasion resistance make it a preferred choice for applications that involve frequent contact with rough surfaces, such as tires, conveyor belts, and shoe soles.

Elasticity and Compression Set

EPDM exhibits excellent elasticity, allowing it to recover its original shape after being stretched or compressed. It also has a low compression set, meaning it can maintain its shape and sealing properties over time. SBR, while still elastic, has a higher compression set compared to EPDM. This makes EPDM more suitable for applications that require long-term sealing performance, such as gaskets and O-rings.

Electrical Insulation

EPDM possesses good electrical insulation properties, making it suitable for applications in the electrical industry. It can effectively resist the flow of electric current, reducing the risk of electrical shocks and short circuits. SBR, on the other hand, has lower electrical insulation properties compared to EPDM, limiting its use in electrical applications.

Cost and Availability

In terms of cost, SBR is generally more affordable compared to EPDM. SBR is widely produced and readily available, making it a cost-effective choice for various applications. EPDM, on the other hand, is slightly more expensive due to its superior properties and limited production capacity. However, the availability of both materials may vary depending on the region and specific requirements.

Conclusion

EPDM and SBR are both versatile synthetic rubbers with unique attributes that make them suitable for different applications. EPDM excels in weathering resistance, flexibility, and chemical resistance, making it ideal for outdoor and chemical industry applications. SBR, on the other hand, offers superior hardness, abrasion resistance, and cost-effectiveness, making it a preferred choice for applications like tires and conveyor belts. Understanding the specific requirements of your application will help you determine whether EPDM or SBR is the right choice for your needs.