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!

*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.

Jobs

Most creep resistant rubber?

Most creep resistant rubber?

(OP)
I need something stretchy like a rubber band for holding things together, but it has to be very creep resistant because it needs to withstand a constant ~50% elongation for at least 3-5 years without significantly changing length/tension. I tried it with natural latex rubber but after only a few months it lost its shape and thus, its tension. Note that I did not protect the rubber latex from oxygen, although it was not exposed to UV and was kept indoors mostly so I'm not sure if that's what caused it.

I'm thinking spandex might be suitable but I'm not sure if its creep resistance is superior to natural rubber. Btw, cost is not a problem.

RE: Most creep resistant rubber?

All elastomers will experience creep. You'll need to quantify the amount of tension loss that is allowable, then maybe you will be able to find something allowable.

Would something like this http://www.clampco.com/products/t-bolt-spring.asp work for your application?

RE: Most creep resistant rubber?

(OP)
Not exactly because I need something that is stretchy. I think I'll try a coil spring or something of that sort.

RE: Most creep resistant rubber?

You probably would have gotten better creep results if you did have antioxidant AND antiozonant in the rubber. Have you considered contacting a rubber band manufacturer (e.g., Alliance Rubber http://www.rubberband.com/) to see if they have a product that'd work for you?

RE: Most creep resistant rubber?

(OP)
What kind of chemicals and at what concentrations would protect natural rubber from oxygen and ozone like you suggested?

RE: Most creep resistant rubber?

I don't work with NR latex, and haven't really worked with solid NR in a while, but there's a fair amount of info available from rubber chemical suppliers like Lanxess, RT Vanderbilt, Akrochem. The antiozonant 77PD (sold by several companies with different tradenames; Flexzone 7 and Vulkanox 4030 are two that I recall) seems to be a good antiozonant as well as providing antioxidant properties, although it's a staining material. I'd suggest you contact one of the rubber chemcial suppliers for their recommendations.
Good Luck!

RE: Most creep resistant rubber?

You will not find a rubber that meets your stated requirements. Only a metal or composite spring will work.

RE: Most creep resistant rubber?

For low levels of creep in an NR compound you need a fairly high filler level (e.g. 70-ish phr N772), a really tight cure system (probably an EV one based on sulfur-donors such as TMTD or a urethane-type system based on TARRC's Novor 924), 2 or 3 phr 6PPD and 1.5phr TMQ.

RE: Most creep resistant rubber?

In the absence of any ageing, a well cured gum or lightly filled natural rubber formulation should provide the best resistance to creep/stress relaxation among different elastomers. But ageing will occur in practice to the detriment of resistance. Even diffuse light can lead to photo-oxidation and that is a major reason why a traditional rubber band perishes. It is not designed to last long. Ozone attack is another threat for a stretched product. As others have said, resistance can be raised by adding antidegradants, and light ageing can be reduced quite effectively by a light loading of a reinforcing black which performs as a UV absorber. The antiozonant needs to be of the dialkyl p-phenylenediamine type in order to raise threshold strain. 6PPD, an alkyl, aryl type, can be used but needs the assistance of wax. However, natural rubber may not be the best choice overall and polychloroprene (neoprene) may be a better starting point. I would not have thought spandex was an option for creep resistance.

In many ways I share Compositepro's view that a metal spring might be a better solution.

I not sure I agree with GrahamBennett that a high level of black will help, because fillers usually increase creep/stress relaxation, not withstanding the change in stiffness.

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


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close