Acrylic Stress Fractures

[Chris Windebank]

what did you clean it with? meths?

[Phil Green]

Not that I know of, was wondering if it could be the acrylic adhesive on the vinyl

[Karl Williams]

Did the acrylic cool down to fast? I’ve seen people do this and the acrylic either catch fire or start to melt and they do the daft thing like chucking it in water causing it to crack.

[Phil Green]

We flame polished them and left them standing for a few weeks, then started to apply the graphics Friday then came in this morning and found all the chips/cracks

[John Harding]

im with Chris most likely whatever was used to clean the acrylic rather than the vinyl

John

[David Rogers]

Even the lightest wipe over with any fluid containing solvents causes stress crazing.

Not a lot you can do about it afraid to say.

(Been there done that!!)

Dave

[David Rowland]

i would say cleaning too.

think my colleagues have said that different nozzles sometimes helps.

[Fred McLean]

was looking on wiki the other day and clicked on plexiglass i think it was, says heating it put stress fractures into it so there is nothing you can do, i think it did mention cleaning it after with anything but water would highlight them!! 😀

[Gert du Preez]

Flame polish and solvents……

We did a test with a supplier one day. The cracks appeared as if on command!

Cant remember if it was on Plexi or Perspex. Dont care, since I dont flame polish 😉

[Steve Halvorsen]

I was told a good few years ago by the Acrylic supplier when this happened to us that by heating the acrylic or perspex you are putting the edge under stress by flame polishing and by wiping with the slightest amount of cleaning spirit releases the tension in the edge which results in these fractures.I was advised to only ever clean with water or a dry cloth.

[Steve McAdie]

This is a handy pdf to save for later reference.

http://www.perspex.co.uk/documents/tech … crylic.pdf

Steve

[Chris Wool]

thanks for that Steve very handy.

do you think laser cutting is similar to flame edges in this context.

[Steve McAdie]

Some work I do is for a photography/framing place and they mount loads of prints to laser cut acrylic about 10mm thick and never get stress fractures, the laser also leaves a very neat bevel.

[Steve McAdie]

Chris it does mention about laser cutting on page 2 left hand column. Seems unless bonding the acrylic edge no further treatment is necessary.

[Phillip Grundy]

Hi
we have a laser here and wen you cut through the sheet it is about 1400 degrees at the cutting point so it puts a lot of stress into the acrylic especially if it is cutting slow due to a lower power laser.
Cast is a lot more forgiving than extruded but put any sort of solvent cleaner on it e.g. rapid tack and boom it could even split a small panel in half.
Use nothing but h2o on it…
Saw cut and flamed is not so bad & gluing laser cut edges can cause a lot of edge crazing to.
For a better edge laser then diamond edge polish.
Phil

[Steve Hooper]

I know this is an old thread but I have found that cleaning acrylic that has been lasered or flame polished is okay if using white spirit. Any alcohol-based solvent can/will lead to either micro-cracking or total failure.
🙂

[David Rogers]

White spirits (UK) is more mineral oil based so may require further cleaning with detergents to get rid of that if applying graphics.

In the US…white spirits can also be a name for ‘meths’.

[Steve Hooper]

If applying over the acrylic, yes, a detergent would be needed but it can be a lot easier than trying to anneal the workpiece.

In the US I think the UK ‘White Spirit’ is VM&P.

Some white spirits in the UK have a greater concentration of naptha. 🙂

[david hogg]

I have read all the comments and I thought i would add my 2 cents worth
The problem is stress cracking and there are a number of things that can cause it , first thing is to check if the material is cast or extruded, cast acrylic is twice as good as extruded personally I don’t buy or supply people anything else than cast. Next thing is to make sure you buy a good brand of acrylic, ICI Perspex and Autlglss are the top 2
Manufactures , you be surprised at the different manufactures qualities , when you flame polish acrylic you are stressing the edge of the acrylic you are meant to anneal the acrylic after polishing this to relive the stress that was introduced when polishing but very few people have an acrylic oven in which they can do this, the main thing is do not use meths it does work on good branded acrylic but it will crack the edge on poor quality
Use warm soapy water to clean or apply graphics white spirits does work well but can leave a mist on the acrylic so this should be used in extreme cases but I have used it myself and works ok for problem areas , laser cutting is just the same as flame polishing add all the same problems I know I have a laser machine which is used for acrylic stick to water and you will have no problems, sorry could talk about this a lot more been there seen it all done must of it
Any more advice let me know contact me directly dave

Please take a moment to read our Board Rules