viscosity of polyamide after heat-aging
viscosity of polyamide after heat-aging
(OP)
I have noticed a "strange" behaviour of a molded PA12 GF30 part.
The viscosity of the material after heat storage 1000h/150°C is higher than the original value.
Normally the molecules should be damaged and as a result of this effect the viscosity should be lower.
The viscosity was measured with an Ubbelohde-viscometer.
Has someone an idea what happened?
Thanks
Hacki
The viscosity of the material after heat storage 1000h/150°C is higher than the original value.
Normally the molecules should be damaged and as a result of this effect the viscosity should be lower.
The viscosity was measured with an Ubbelohde-viscometer.
Has someone an idea what happened?
Thanks
Hacki





RE: viscosity of polyamide after heat-aging
Your 1000h at 150°C probably removes a lot of the water and that may affect the viscosity measurements. In effect your measurements before heat treatment are done in solvent plus water (from the nylon) whereas your measurements after ageing are done in pure solvent. So your effective solvent is not the same in both cases, the affinity of the nylon will be different in both cases and so the radius of gyration of the solvated nylon and its viscosity may be different.
Alternatively it may be that the nylon cross-links lightly on ageing. Not all polymers undergo chain scission on heat ageing, some cross-link. From memory for example PP undergoes chain scission but PE cross-links.
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: viscosity of polyamide after heat-aging
I would expect that effect to me somewhat greater than the drying out with nylon 12 as nylon 12 has somewhat less affinity for water than more common nylons.
Regards
eng-tips, by professional engineers for professional engineers
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RE: viscosity of polyamide after heat-aging
Have you tried adding stabilisers? I think copper iodide and hindered phenolics are usual for nylons.
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: viscosity of polyamide after heat-aging
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: viscosity of polyamide after heat-aging
I think the "crosslink and oxidation -thing" is a
possible answer.
The water absorbtion is definetly not the reason because we
measured the amount of volatile components in the material before the "Visco-Test".
(Before visco-testing the original material and before visco-testing the conditioned material.)
We also found that the aged material was not completely
solved in the solvent. We found small amounts of "non-soluble" nylon.
Hacki
RE: viscosity of polyamide after heat-aging
This is starting to sound a bit like a student post.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: viscosity of polyamide after heat-aging
"Material-lab tester for initial samples-post"
We must make such tests according to customer-specifications
in the automotive industry.
Though we are a traditional elastomeric components company
we have more and more plastics in our products and sometimes we must ask these questions.
I could have asked some of our specialists at the companies that selled us our testing equipement but then I wait for days for an answer...
And this forum is a good place for a quick and qualified answer!
thanks
Hacki