×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Nitrile Failing in Hydraulic Oil

Nitrile Failing in Hydraulic Oil

Nitrile Failing in Hydraulic Oil

(OP)
I am using a die cut nitrile bumper .25" thick inside of a shock absorber for an internal extension cushion. Some have failed some have not. When the part does fail its catastrophic destroying all the internals of the shock absorber due to contamination which plugs the ports, bends/breaks shims and makes a non damping unit.

 I am trying to figure out why nitrile is failing in oil where it is supposed to be compatibile with and when the seals sealing the shock are nitrile...

Temps range from 60F to 150F..180F rarely so it is within the temp ranges of the material and the seals, sealing the shock are nitrile and we have never seen a failure.

Any help is appreciated. The bumper supplier and seal supplier are not the same.

RE: Nitrile Failing in Hydraulic Oil

Could you better describe the failure of the die cut part? Does it swell, shrink or just break up?

RE: Nitrile Failing in Hydraulic Oil

(OP)
It swells and breaks up. Failure looks identical to rubber submerged in oil that is agitated...nothing but pieces/chunks left and the oil is compleltly contaminated/black.

The cushion sees a compression loading of roughly 2000lbs everytime the tire unloads.

RE: Nitrile Failing in Hydraulic Oil

First verify that it is in fact made from nitrile rubber. An FTIR analysis would tell you this. If it is, you will have to dig deeper. Look at state of cure. Find out what plasticizers are used in the rubber compound.

RE: Nitrile Failing in Hydraulic Oil

I agree about verifying that the rubber is indeed nitrile rubber. If it is, there can be significant differences between the quality of different nitrile rubber compounds. I'm assuming you're buying the nitrile rubber from a supplier and it's not your formula.
Nitrile rubber, the base rubber I'm talking about here, not compounds, comes in slightly different compositions, varying in the levels of acryloNITRILE and butadiene that are used to polymerize into nitrile (or NBR) rubber. Higher acrylonitrile (ACN), the better the oil and probably hydraulic fluid resistance. Higher butadiene, better low temperature properties, but poorer oil resistance. Also, compounds can be cheapened by adding higher amounts of fillers and plasticizers, giving poorer strength properties. Some compounds that don't need as good oil resistance can have other rubbers (e.g., polybutadiene or SBR rubbers) blended with it, as these are generally less expensive than nitrile rubber.

Regards,
tom

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources