Styrene Butadiene Rubber (SBR)

Styrene Butadiene Rubber (SBR) is a widely used synthetic rubber produced through the polymerisation of styrene and butadiene monomers. It was originally developed as a substitute for natural rubber and has since become one of the most commonly used synthetic rubber compounds in the industry.

SBR is valued for its excellent abrasion resistance, good tensile strength, and reliable performance in a wide range of general-purpose applications. It also offers good ageing stability when protected with suitable additives, making it a cost-effective choice for many moulded components such as gaskets, seals, bumpers, and mats. While it does not perform well against oils, fuels, or ozone exposure, SBR remains a popular material for parts that require durability and resilience in dry or water-based environments.

Styrene Butadiene Rubber (SBR) is commonly used in a broad range of moulded rubber products due to its balance of performance, availability, and cost-effectiveness. One of its most prominent uses is in the automotive industry, particularly in the manufacture of tyres, where its abrasion resistance and durability are essential.

Beyond tyres, SBR is frequently moulded into gaskets, seals, and rubber mats, making it a popular choice for both industrial and consumer products. Its ability to absorb shock and resist wear also makes it suitable for vibration-damping components and flexible mounts. Additionally, SBR is used in hoses, belts, and other items where flexibility and resilience are important under moderate operating conditions. These applications benefit from SBR’s relatively low cost, consistent quality, and good mechanical properties, especially where oil and chemical resistance are not critical.

In rubber molding, Styrene Butadiene Rubber (SBR) and natural rubber each offer distinct advantages, making the choice between them dependent on the specific application requirements. SBR typically provides better heat resistance and superior abrasion resistance compared to natural rubber, which makes it more suitable for components exposed to friction or elevated temperatures over time.

However, natural rubber generally outperforms SBR in terms of tensile strength, elasticity, and overall flexibility, which can be crucial in applications requiring high resilience or dynamic movement. Another key difference is consistency. Because SBR is synthetically produced, it delivers more uniform properties from batch to batch. This consistency is a major advantage in high-volume moulding operations, where maintaining quality control is essential.

Styrene Butadiene Rubber (SBR) has moderate heat resistance and can typically withstand continuous operating temperatures of up to 100°C (212°F). This makes it suitable for many general-purpose applications where heat exposure is intermittent or remains within this range.

However, SBR is not recommended for prolonged exposure to high temperatures. Over time, it can degrade, harden, or lose flexibility.

For applications involving sustained heat or thermal cycling, SBR may not be suitable. In environments above 100°C, alternative materials like EPDM (Ethylene Propylene Diene Monomer) or silicone rubber are better options. They provide superior heat resistance and long-term stability.

When designing moulded rubber components for elevated temperature environments, several factors must be considered. It’s important to look beyond just the peak temperatures. You should also account for the duration of heat exposure. Additionally, consider any contact with oils or chemicals, as these can further affect the rubber’s integrity.

Styrene Butadiene Rubber (SBR) can be formulated to achieve a wide range of hardness levels, typically spanning from 40 to 90 Shore A. This flexibility allows manufacturers to tailor the rubber’s firmness and resilience to suit different moulded product requirements.

Softer compounds in the 40–60 Shore A range are ideal for applications that require flexibility, cushioning, or vibration absorption, such as gaskets, seals, and padding components. On the other hand, harder formulations ranging from 70 to 90 Shore A provide greater rigidity and wear resistance. These are ideal for components that must keep their shape under pressure. This includes parts such as rollers, bumpers, and structural rubber elements that endure regular mechanical stress.

Manufacturers can customise the hardness of SBR mouldings by adjusting the compound formulation and curing process. This allows them to meet specific performance requirements. It also helps balance key properties such as durability, compression set, and tactile feel to suit the intended application.

SBR can be processed using compression, transfer, or injection moulding, depending on part complexity and production volume. Compression is common for simple shapes like gaskets, while injection moulding is preferred for high-volume, precision parts. Transfer moulding suits intermediate needs with more intricate geometries.