How To Anneal PC - Lexan HP1R??
How To Anneal PC - Lexan HP1R??
(OP)
I was wondering if anyone could let me know the best way to easily anneal Lexan HP1R or even knew its Tg? I found some sites saying heat to 250F for an hour but that was for Polycarbonates in general. Any help appreciated, thanks!





RE: How To Anneal PC - Lexan HP1R??
Table of Tg for thermoplastics http://www.azom.com/details.asp?ArticleID=83
According to that Tg of polycarbonet is 150°C so anneal somewhat below that.
And now for a question. Why are you using polycarbonate and not some other polymer? Why do you need to anneal it? Polycarbonate has a lot of stresses built in after moulding, some other transparent polymers don't. As an example MABS has much better flow and much lower stress than PC (as measured under polarised light). Also PC has poor ESCR. Yet another thing most people don't know is that the exceptionally good impact resistance of PC is only true for thin parts (3mm or less).
RE: How To Anneal PC - Lexan HP1R??
There are processimg methods to help reduce stress in PC before making the finished part. You don't say how your parts are processed but in general hotter molds or dies will help. Typically HP1 is an injection molding material.
D3 brings up some good points about clear materials. If you are using an HP grade of LEXAN than you must be making medical type parts so changing may be an issue. Also PC does have a critical thickness as D3 mentions however I found it to be about 4.5mm where it becomes brittle. That's 4.5mm for average flow (around 12 MFR) and as the flow goes up the critical thickness drops. HP1 runs about 25 MFR. You can see this if you look at "bullet-proof glass" using PC. Look at the thick panel and you will see layers of 4mm sheets stacked together to make the panel.
Mike
RE: How To Anneal PC - Lexan HP1R??
RE: How To Anneal PC - Lexan HP1R??
JT
RE: How To Anneal PC - Lexan HP1R??
Cannot autoclave it (same as Terlux), but can be radiation sterilized. Don't think can be ETO'd either.
Rgds
Harry
RE: How To Anneal PC - Lexan HP1R??
RE: How To Anneal PC - Lexan HP1R??
RE: How To Anneal PC - Lexan HP1R??
RE: How To Anneal PC - Lexan HP1R??
PC is very prone to solvent stress cracking. This can be triggered by many factors. Much more info is needed if the answers are to be more than generalised guesses. Many factors have for and against aspects.
General suggestions.
Increase in molecular weight, decrease in melt flow index, increase in melt viscosity (call it what you like) increases stress crack resistance, but also increases risk of inducing residual stress.
Adding a mould release decreases solvent stress crack resistance, but might help reduce residual stress.
Any additive, including colours can effect the physical properties and moulding characteristics. PC is especially sensitive to this.
Many very common solvents can stress crack polycarbonate. Sometimes these are in the form of impurities in commercial grades of products, but not in the AR grade, so they don't show up in lab tests if AR grade rather than commercial grade reagents are used.
PC is especially susceptible to even traces of aromatic hydrocarbons and chlorinated hydrocarbons. You might find these in lubricants, fuels, candle wax, cleaning reagents, cosmetics, food, insect repellents, paints, adhesives etc.
Regards
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RE: How To Anneal PC - Lexan HP1R??