Annealing Polycarbonate

[JPC10]

My question is in relation to annealing. Would excessive annealing cause degradation provide the temperature is kept 30C below the glass transition temperature Tg?

 

[patprimmer]

Yes, especially if it absorbs water before annealing.

You can get hydrolysis when heated in the presence of water.

You can get oxidation when heated in the presence of air.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[Demon3]

I presume you want to anneal it to remove built-in stresses from cooling of the part. Polycarbonate is susceptible to such stresses. If that is why you want to anneal, have you considered using another plastic that is less prone to develop such stresses or perhaps adjust your cooling regime?

 

[Pud]

from "Plastics Materials", J A Brydson, fifth edition 1989,

page 538, Chapter 20, Polycarbonates:

"In general, moulding strain will be reduced by using high melt temperatures, preplasticing machines, high injection rates, hot moulds (around 100C) and, where used, inserts should be hot. Annealing at up to 125C for up to 24 hrs will be of some value."


Cheers

Harry

 

[Demon3]

Nice contribution Harry. That's one of the best plastics books ever. I have the 7th edition on my desk.

 

[Pud]

Hi Demon3,

Indeed. I though it a rather odd question so looked it up the old fashioned way!

Brydson was Head of Department at the (as was) North London polytechnic when my wife did her whatever it was there a few years ago (must have been late 70's.) Crap lecturer apparently... Haven't bothered with a later version as they're all the same as far as I can make out!

Harry

 

[patprimmer]

I read the question as he knows how to anneal PC, but wants to do it repeatedly after reintroducing stress ad wondered if repeated annealing would eventual damage the material.

My answer on how to do it once would have been read the manufacturers literature. I know both GE and Bayer had good literature on this. I can't be bothered checking their current names as a simple google search by the OP would have answered that question.

By the way I agree completely with both Demon3 and Puds answers.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[Pud]

Hey Pat,

You're right! A "proper" read after your comment makes the post have a very different perspective on the question!

I bet you're great on conspiracy theories! (joke) Or are you just a cynic? Strange application if so - perhaps the op might like to elucidate on the application?

(Deafening silence ensues...)

Cheers

Harry

 

[patprimmer]

Excessive was the word I reacted to however it is not really clear what he really means

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers