Classified by Acrylonitrile (ACN) Content
This is the primary classification method for nitrile rubber, as it directly determines key properties such as oil resistance and low-temperature flexibility:
Low-nitrile type: ACN content ≤24%; offers excellent elasticity and low-temperature resistance; suitable for flexible parts requiring frequent bending.
Medium-nitrile type:ACN content 25%–30%; balances oil resistance and elasticity; the mainstream choice for general-purpose seals.
Medium-high-nitrile type:ACN content 31%–35%; offers enhanced oil resistance; commonly used for standard oil-resistant hoses and rubber rollers.
High-nitrile type:ACN content 36%–41%; features outstanding fuel resistance; suitable for seals in automotive fuel systems.
Ultra-high-nitrile type: ACN content ≥42%; offers exceptional oil resistance and gas impermeability (approaching that of butyl rubber); suitable for extreme oil-resistance applications.
Classified by Polymerization Process
High-temperature polymerized NBR: Polymerization temperature of 30–50°C; an older, traditional process; raw rubber Mooney viscosity fluctuates significantly; rarely produced on a large scale nowadays.
Low-temperature polymerized NBR: Polymerization temperature of 5–15°C; the current mainstream production process; yields products with regular molecular structures and more stable physical and mechanical properties.
