Properties of PE-HD

[EdClymer]

Can anyone suggest a source for;

Stress plotted against strain for varying times say 1 year, 10 years and 20 years? at say 20°C.

Better still a family of curves at varying temperatures, say 20°C, 30°C and 50°C.

I need to determine the tangent Modulus and the secant Modulus for black PE-HD as used for manufacture of chemical storage vessels.

Many Thanks

Ed


Ed Clymer
Resinfab & Associates
England

 

[dwightdixon]

I do not know of any independent testing but you could contact the major suppliers for this creep data. It is not going to be very uniform. Most big tanks are rotomolded and likely contain a cross link agent which makes things a lot different. Are you sure what resin they used when they made the tanks?

 

[EdClymer]

Dwight

In UK we build large vessels to 80-100 m3 from sheet.

Sheet manufacturers are in general not helpful with data - but we are still trying.

If anyone knows of good source - would be appreciated

Ed

Ed Clymer
Resinfab & Associates
England

 

[ARenko]

If you know the particular resin used, the best place to go is the resin supplier. Even if you don't know the particular resin, you could go to a resin supplier (e.g. exxon mobil, chevron phillips, bp solvay, etc...) with the information that it is HDPE for chemical storage vessels and they may be able to help with some general information.

 

[ARenko]

Here's a resin that might apply...

http://www.cpchem.com/tds_unsecured/60B6692A8E654025A6CBDF3BF49CE595.pdf

They mention large containers and creep resistance, so I assume they have creep data.

 

[patprimmer]

I would also expect that the major resin manufacturers would be the only source of extended creep data.

Their older literature is a more likely source, as the modern marketing trend is to remove obstacles, like complicated looking data from the literature.

I will look in my collection, but I fear I only have it for nylon.


Be careful that the data you use is for a grade with similar density, similar vinyl acetate content if any, and similar melt flow index. Sheet extrusion grade is normally very low melt flow index, which will give a somewhat higher elongation than the more often quoted injection moulding grades.


Regards
pat pprimmer@acay.com.au
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[EdClymer]

Thanks to djv and pprimmer for their help.

The root of problem, is that sheet extruders do not know (or will not say!) which grades and who are producers of the polymers they use.

The search continues: if any one has information it would still be appreciated. The DVS 2205 code does produce graphs (repeated in BS EN 1778 and EN 12573) could anyone comment on accuracy?

Regards

Ed



Ed Clymer
Resinfab & Associates
England

 

[stanier]

Ed,

You might try Borealis in Europe or Chevron Phillips Chemical Company in the USA.

The problem is that the values of modulus will vary depending upon the loading and the rate of loading. The stress/strain relationship will be non linear.

You might use FEA to get answers to the ninth decimal place and then add a 50% safety factor because of he vagaries of the properties of the material.

Any modelling will need the properties changed to check the design sensitivity. So the initial starting values dont have to be that precise.