Cellulose Acetate Degradation

[TConservatorSI]

I have some cellulose acetate that is degrading. It has become very brittle. I was thinking that it is from glycosidic cleavage of the polymer, but I do not know what is causing this. Also what causes plasticizers (Diethyl Phthalate and Dimethyl Phthalate and Triphenyl Phosphate to leech out? Is it the hydrolysis of the Acetate groups causing acetic acid that makes the plasticizer come out or does it just come out on its own after a certain amount of time. Is ther a certain material that will cause the plasticizer to come out faster than it normally would?

 

[patprimmer]

Loss of plasticiser, UV light degradation and thermal degradation will all send cellulose acetate brittle.

The plasticiser migrates out in an attempt for it to reach equilibrium with it's surroundings. Higher molecular weight plasticisers or less active molecules leach out at a slower rate. Cellulose acetate is particularly sensitive to UV light.

Regards

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[Demon3]

The bad news is that if it became brittle due to heat or UV then it's irreversible. The good news is that if it became brittle due to plasticiser loss then you may be able to fix it if you can diffuse some plasticiser back in there. It would have to be the right type. Check the net or maybe as Eastman.


There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[TConservatorSI]

I actually had some of the plasticizer that was leaching out analyzed on FT-IR and it came back as a mix of triphenyl phosphate and dimethyl phthalate. The thing is that there is severe cracking on some of the samples, one sample actually had a piece break off and yet on others they are perfectly ok.

And yet there is no vinegar smell on any of the samples at all. Does anyone think that all this cracking and brittleness came from just the loss of the plasticizer? Because if the Cellulose Acetate was degrading then there should at least be a vinegar smell which indicates the acetate groups being hydrolyzed.

I will be running Raman-IR on the samples soon to make sure that the information that I recieved was correct in the fact that they are cellulose acetate.

Also any opinions on certain elements that were used to achieve different pigments having an effect on the degradation? The samples are being analyzed with an XRF.

Please, any thoughts on Cellulose Acetate degradation would be helpful!

Thanks

 

[patprimmer]

Pigments can have a profound effect by several mechanisms.

They can act as nucleating agents having an effect on degree of crystallinity and size and shape of crystals. Even some so called amorphous polymers have some nano sized crystals.

They can act as a catalyst to oxidation, cross linking or any other reaction. Many colorants contain metals.

They can act as a blind to protect the matrix from UV attack.

They can effect the temperature as visible light is absorbed and converted to heat, or is reflected to various degrees.

Regards

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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.