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help please having problems floodcoating acrylic
Doing a job as we speak where we have to floodcoat 10m acrylic with frosted vinyl. The acrylic has been flame polished and radiused corners.
Problem
We are coating them using our easy taper with the minimum of pressure but we are starting to find loads of little stress fractures on the edge. Any tips or are we going to have to do 30 off 5′ x 4′ floodcoated acrylic sheets by hand 🙁
G
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13 Replies
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Haven’t cleaned them with meths? 😮
Or is it defo crush fractures!!! -
You sure they’re stress fractures?
We thought that for a while and couldn’t get the bloody things to stop appearing. Then… we realised it was because we were cleaning the boards with meths before applying vinyl 😳 -
why what does the meths do? 😳
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Get you pi$$ed if you drink too much :lol1:
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cheers Dave but why does meths mess up flame polished edges???
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Flame polishing opens up the cellular structure of the acrylic, allowing ingress of the chemical cleaner (meths in this case) into the exposed edges of the acrylic – best just to wipe down with warm water on flame polished panels.
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We’ve had this too. 🙁
You’ll get these fractures anywhere the sheet has been cut, drilled, or machined in any way.
We only clean with plain water, not even any soap.
Generally acrylic panels are supplied to us by the customer and we always impress on them that unless the panels have been annealed after cutting there is no way we will guarantee that cracking will not occur.
As always, some listen and some don’t.
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If it is just the ingress of the meths into existing cracks/defects in the acrylic it will be the light that actually allows you to see them then. If that is the case surely once the meths has evaporated they will disappear.
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quote martin:If it is just the ingress of the meths into existing cracks/defects in the acrylic it will be the light that actually allows you to see them then. If that is the case surely once the meths has evaporated they will disappear.
Doesn’t work like that Martin.
They are stress fractures and they just get larger and longer over a very short period of time.
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John, in that case I would have thought you were going to see them anyway, don’t use much acrylic myself so haven’t come across this before or haven’t noticed it anyway.
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Hi All,
As pointed out above flame polishing causes a lot of internal fractures in the acrylic and meths for some reason makes this worse – A trade friend of mine recently fitted out a leisure centre/spa with a couple of hundred acrylic panels with flamed edges, a week later they were all "crazed" from chlorine in the swimming pool! so be careful
cheers
mike -
There are 2 types of acrylic , cell cast and extruded. The cell cast is a long polymer chain and the Extruded is short. Both of them get stressed with any heat operation on them , Flame polishing and lasering are the worst culprits. This is not a problem generally unless there is a solvent applied or indeed , even nearbye , solvent fumes can cause the stress cracking (not all solvents) The solvents break the polymer chains bonds apart and the shorter the chain , the worse it gets.
Cast acrylic is far better in this regard , however it is more expensive and less dimensionally precise than extruded.
One can stop stress cracking by annealing the pex , that is , heating it to about 80 degrees c for one hour per mm thickness and letting it air cool.
The worst part about all this is that you can ship a perfect part , and it can still stress crack months later.
A lot of problems are caused by wrong manudfacturing methods , for example , flame polishing should be done with a specialised torch using hydrogen and oxygen , not something like methane. Most stress problems can be minimised if the temperatures used are correct and the operator limits any heat affected zones.
In terms of cleaning pex , well that is a whole saga.
There are 2 problems , 1) removing stuck on dirt (a commercial plastic cleaner like novus 1/2 is good)
2) Static – as soon as you rub clean pex , you are going to charge it and it will attract a ton of dust and swarf which will make applying anything to it difficult. Ideally an ionising air gun is the best solution , but using an anti static polish like novus 1 will help here too.
Warm soapy water is the next best thing. -
Thanks for all your input guys…one thing sticks in my throat that the people who flame polished said items have been doing it for many years so why no warning off them??? DO NOT USE SOLVENTS TO CLEAN would be a good sticker on each piece
oh well we live and learn
Thanks all again
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