Full definition
BR rubber, or polybutadiene rubber, is a synthetic elastomer created through the polymerization of 1,3-butadiene. Known for its remarkable resilience, BR rubber can achieve rebound elasticity rates of up to 85%. This characteristic makes it highly desirable in applications where impact resistance and durability are critical. Additionally, BR exhibits minimal heat buildup under dynamic loads, which is crucial in high-performance scenarios. Its low-temperature flexibility is notable, with a glass transition temperature (Tg) ranging from -100°C to -110°C, outperforming many other diene rubbers in cold environments. The material demonstrates abrasion resistance comparable to natural rubber (NR) but features a tensile strength that ranges from 8 to 17 MPa—lower than that of NR in its unfilled state. The elongation at break for BR rubber is impressive, ranging between 300% to 600%, which provides further versatility in various applications.
Despite its desirable properties, BR rubber alone has limitations in processability and tackiness, which necessitates blending with other elastomers for optimal performance. Typically, BR is blended with 20-40% natural rubber (NR) or styrene-butadiene rubber (SBR) to enhance resilience and improve low-temperature performance. This blending approach is critical in achieving the right balance of mechanical properties for specific applications. The ASTM D2000 classification for BR rubber is AA, indicating its standard quality in industrial applications.
The primary applications of BR rubber are in the automotive and industrial sectors. It is predominantly used in tire treads and sidewalls, where durability and performance are paramount. Other applications include industrial flooring, conveyor belt covers, golf ball cores, shoe soles, and vibration isolation mounts. The choice of catalyst during production can also influence the microstructure of the rubber; high-cis BR (>96% cis content) is produced using Nd or Co catalysts for enhanced elasticity, while medium-cis BR is easier to process and is produced using Li catalysts. With an annual global production of approximately 3 million tonnes, BR rubber continues to be a vital material in modern manufacturing and production processes.