General Properties
Short Name:
Name:
NBR
Acrylonitrile-butadiene rubber
Acrylonitrile butadiene rubber (NBR) is obtained by copolymerization of acrylonitrile (ACN, the content varies between approx. 20 to 50% in commercial products) and 1,3 butadiene. The ACN content significantly influences the properties of the NBR vulca- nizate. Carbon black is often used as fi ller material. Just like NR, CR or SBR, NBR belongs to the R group of rubbers, i.e., to the group with an unsaturated hydrogen carbon chain (classification in accordance with ISO 1629 or ASTM D1418).
Structural Formula
Properties
| Glass Transition Temperature | -44 to 5°C |
|---|---|
| Melting Temperature | - |
| Melting Enthalpy | - |
| Decomposition Temperature | 450 to 475°C |
| Young's Modulus | 2 to 5 MPa |
| Coefficient of Linear Thermal Expansion | 150 to 180 *10-6/K |
| Specific Heat Capacity | 1.93 to 1.96 J/(g*K) |
| Thermal Conductivity | - |
| Density | 1.00 g/cm³ |
| Morphology | Amorphous rubber |
| General properties | Good abrasion resistance. Good temperature resistance. Very good resistance to fuels, mineral oils, lubricating greases, vegetable and animal fats and oils |
| Processing | Cross-linking by means of sulfur (with accelerator) |
| Applications | Apparatus engineering (e.g., seals, O-rings). Automobile industry (e.g., brake pads, clutches). Packaging industry. Rubber gloves |
NETZSCH Measurement
| Instrument | DSC 204 F1 Phoenix® |
| Sample Mass | 11.47 mg |
| Isothermal Phase | 7 min |
| Heating/Colling Rates | 10 K/min |
| Crucible | Al, pierced lid |
| Atmosphere | N2 (40 ml/min) |
Evaluation
In this case, NBR has a slightly lower glass transition temperature (-29°C, midpoint, 2nd heating, red) and a slightly lower Δcp (0.29 J/(g.K)) than in the HNBR (Tg -23°C, Δcp 0.38 J/(g.K)) example on the previous pages. The glass transition is overlapped by a slight RelaxationWhen a constant strain is applied to a rubber compound, the force necessary to maintain that strain is not constant but decreases with time; this behavior is known as stress relaxation. The process responsible for stress relaxation can be physical or chemical, and under normal conditions, both will occur at the same time. relaxation.