Creep Limit of Polymers 1

[kreker]

I have a situation where I have a polymer that is continuously loaded and I need to look at creep. If I model it as a cantilever beam the extreme fiber stress is 441 psi. I've done some research and found that if this stress is below the "creep limit" I do not need to be concerned with creep but I'm having a tough time finding that information. First, is my approach correct by just finding the stress and making sure it is below the "creep limit"? Second, does anyone know a good place to find that information for the following:

Polypropylene, Homopolymer
Celcon M90 (Acetal, Delrin)
Nylon 66/6

I'm currently working with my vendors, etc. but I'm hoping someone out there can shed some light on the situation. Thanks!

Kevin

 

[borjame]

Most materials do not have a "creep limit", creep is a function of temperature, stress, and time not just stress. Creep occurs only when the load is applied at a temp above 1/2 of the melt temp of the material, below that temp another phenomenom is at work (fatigue typically). I have no experience with the material in question, but I wanted to be sure you looking for the correct data.

 

[Tofflemire]

Hi Kreker,

We use a material called Torlon 4203, extruded polyamide-imide. This has very good creep properties. We use in a product that is submerged to 1000 PSI for extended periods of time.

Tofflemire

 

[barbless]

Kreker, I have an old Delrin design handbook by DUPONT (1967). The information you are looking for is contained within. However, the data are for the various compositions of delrin acetal resins so I don't know if it will be of any help to you