UV Curable Adhesive on Polycarbonate

[ChrisB41]

Hi all. Want to adhere a PCB to a clear polycarbonate housing. Currently looking at UV curable adhesives.
Has anyone got experience with this?

Is it safe to use UV cured adhesive on polycarbonate, without degradation that may cause part failure?

As I understand it, the adhesive (before it is cured) attacks the Polycarbonate.
But after curing it causes no further damage.
Also UV is known to degrade polycarbonate

So problems may arise if
1. Uncured adhesive is left in contact with the part, causing further damage
2. The degradation caused prior to curing is somehow enough to cause the part to suffer long term failure in the field.


Any insights are appreciated

 

[Demon3]

The UV used will not damage the polycarbonate but the fluid can attack the PC. Check with e.g. Loctite who have detailed guides online to help select the right adhesive for each substrate.

Dr. Chris DeArmitt

Plastics consultant to the Fortune 500:

http://www.phantomplastics.com

Webinars on plastics, fillers & impact modification:

http://www.plastictraining.com

 

[CoryPad]

Here is an example product from Devcon that is UV curable and suitable for polycarbonate:

http://www.devcon.com/UserFiles/File/Tru-Bond_PB_950.pdf

You should contact multiple manufacturers to get their recommendations. Try Henkel/Loctite, 3M, Reltek, and Devcon.

 

[ChrisB41]

Thanks CoryPad and Dr. DeArmitt
We've done stress tests on PC dog bone samples exposed to the uncured adhesive.
It seems the uncured adhesive being on the polycarb for even 10-20s does some damage, leading to cracking and breakage at lower levels of strain.

But it seems to be the method of adhering things like automotive headlights, which gives me good confidence.
I guess there is little strain in that application (and ours), so the slight damage caused by the adhesive in the 10-20s before it is cured, may be negligible.

Has anyone designed parts adhered this way, who can confirm that it its negligible?
The suppliers say "no damage to polycarbonate parts" but we have observed there is.
Maybe, once the adhesive is cured, it is really reinforcing the (very slightly) damaged polycarbonate.

 

[Demon3]

The adhesive probably causes no chemical damage, i.e. no broken chemical bonds. What happens is called environmental stress cracking whereby the solvent lowers the energy to fail in a brittle manner. If you use the right adhesive there should be no weakening due to that effect. Or, if you were to use the wrong solvent and allow a really long drying time for the solvent to leave that may give good results too. I'd say try adhesives from other companies to find the ones that cause no deterioration in plastic strength.

Dr. Chris DeArmitt

Plastics consultant to the Fortune 500:

http://www.phantomplastics.com

Webinars on plastics, fillers & impact modification:

http://www.plastictraining.com