A Closer Look at Parco’s 4200 Nitrile Seals

Nitrile (NBR) is a copolymer of butadiene and acrylonitrile. Due to its excellent resistance to petroleum products and its ability to be compounded for service over a temperature range of -30°F to +250°F, Nitrile /NBR is the most widely used elastomer in the seal industry today. NBR o-rings are very versatile, inexpensive material which contributes to its wide array of applications.

Let’s start with the 4200-70 General-Purpose Nitrile Seal. What differentiates this material?

1. Excellent Physical Properties

Parco’s 4200-70 70-durometer nitrile O-rings have excellent physical properties. For nearly 40 years, 4200-70 O-rings have been used in a wide variety of  applications with great results. So when you specify 4200-70, rest assured that you’ve made the right choice.

2. Excellent Resistance to Compression Set

To perform properly, seals must resist taking a set from compression after being installed. When a seal takes a set, it no longer exerts force on the mating surfaces, resulting in leakage. A compound with low compression set, like 4200-70, better maintains its elastomeric properties and original thickness, preserving seal integrity. Seals made from Parco’s 4200-70 compound provide excellent resistance to compression set. After testing 4200-70 for 22 hours at 212°F, it had a compression set of only 6 percent.

Compression Set of a Typical Parker 70-Duro Compound

3. Very Good Resistance to a Variety of Fluids

NBR O-ring compounds, like 4200-70, provide very good service in gasoline, crude oil, power steering fluid, hexane, toluene, water, water-based hydraulic fluids, and dilute bases such as sodium hydroxide.

So, what’s the chemical resistance of 4200-70?

  • Automatic Transmission Fluid
  • Crude Oil
  • Gasoline
  • Propane
  • Water

More than 50 percent of sealing needs can be met using nitrile. Its versatile nature might be right for your application and you don’t even know it. Consider NBR before opting for something more complex!


About Parco

Founded in 1941, Parco was the first manufacturer to specialize in O-rings, still one of its primary products. Today, Parco has four modern facilities manufacturing O-rings, custom-molded elastomeric seals, rubber-to-metal bonded parts, and machined metal parts. Their 154,000 square-foot facility in Ontario, California is one of the largest plants in the world making molded rubber seals. The three other facilities in Texas and Louisiana specialize in complex custom-molded elastomeric products, machined metal parts, and machined plastics.


The datasheet for Parco’s 4200-70 can be found by clicking here.

Gallagher Fluid Seals is an authorized distributor for Parco. For more information, contact our engineering department.