HNBR

Introduction to HNBR Rubber

HNBR, or Hydrogenated Nitrile Butadiene Rubber, is produced by hydrogenating the butadiene segments in NBR (Nitrile Butadiene Rubber), which saturates the carbon-carbon double bonds. This process, typically done via selective hydrogenation, reduces unsaturation to as low as 0.9-18%, depending on the grade. The acrylonitrile (ACN) content remains similar to NBR (18-50%), influencing oil resistance. Developed in the 1970s and 1980s, HNBR addresses NBR's limitations in heat, ozone, and aging resistance while retaining excellent oil compatibility. It is compounded with fillers like carbon black, silica, plasticizers, and antioxidants. Grades vary by hydrogenation level: fully hydrogenated for maximum durability, partially for balanced flexibility.

 

Characteristics of HNBR Rubber

HNBR combines NBR's oil resistance with enhanced thermal and environmental stability. Here are its key characteristics:

  1. Mechanical Properties: HNBR has excellent tensile strength (15-30 MPa), elongation at break (200-500%), and abrasion resistance. It offers superior tear strength and low compression set compared to NBR, making it ideal for dynamic seals under stress. Resilience is high, with good flexibility even at low temperatures.
  2. Chemical Resistance: Like NBR, it provides outstanding resistance to oils, fuels, greases, and hydrocarbons due to the polar ACN groups. Hydrogenation improves resistance to oxidative chemicals, acids, and bases. However, it has moderate resistance to polar solvents like ketones and esters.
  3. Thermal Properties: HNBR excels in a wide temperature range of -40°C to +150°C (or up to +175°C for short exposures in some grades). It maintains flexibility at low temperatures and resists heat aging better than NBR, with low heat build-up in dynamic applications.
  4. Durability and Aging: Superior ozone, UV, and weathering resistance due to reduced unsaturation, eliminating the need for antiozonants in many cases. It has excellent resistance to thermo-oxidative degradation, making it suitable for long-term use in aggressive environments.
  5. Processing and Cost: HNBR can be processed via extrusion, injection molding, and compression molding, similar to NBR, but requires careful control due to its higher viscosity. It's more expensive than NBR (often 2-3 times the cost) but offers value in high-performance applications where longevity reduces replacement needs.
  6. Other Properties: Low gas permeability, good adhesion to metals and fabrics, and compatibility with water and hydraulic fluids. It can be vulcanized with peroxides for cleaner cures. Electrical properties are moderate, and it's available in FDA-compliant grades for food contact.

In formulations, HNBR is sometimes blended with other rubbers like EPDM for further ozone resistance or fluoroelastomers for extreme conditions.

 

Applications of HNBR Rubber

HNBR's enhanced properties make it suitable for demanding, high-temperature, and oil-exposed applications across industries:

  1. Automotive Industry: Widely used in timing belts, O-rings, seals, gaskets, and hoses for engines, transmissions, and air conditioning systems, where it withstands heat, oil, and mechanical stress.
  2. Oil and Gas Sector: Critical for downhole seals, packers, and blowout preventers in drilling equipment, handling high pressures, temperatures, and corrosive fluids like H2S and CO2.
  3. Aerospace and Aviation: Employed in fuel system seals, hydraulic components, and vibration dampers due to its resistance to jet fuels and extreme temperatures.
  4. Industrial Machinery: In pumps, compressors, and hydraulic systems for seals and diaphragms that require oil resistance and longevity.
  5. Power Generation: Used in turbine seals and hoses in power plants, especially in biofuel or high-temperature environments.
  6. Other Uses: Medical devices (e.g., seals in equipment), rollers in printing, and consumer goods like high-performance gloves. It's also emerging in electric vehicle batteries for seals exposed to coolants.

HNBR production is growing with advancements in sustainable hydrogenation processes. It's a premium material for applications where failure is costly, with global demand driven by automotive and energy sectors.