chemical welding of polycarbonate 1

[dclnz]

Hi,
I have designed a plastic case such that a base plate snaps into place, but I need to chemically weld the two parts to ensure the final assembly doesn't come apart. What type of glue or compound should I be using? Any ideas or suggestions would be appreciated.
Cheers

 

[prodeng]

We have done something similar here where I work. We discovered some very interesting things. Typically, you can use a cyanoacrylate (check Loctite's web site). One thing about it, though, is that the surfaces adhere better if they're a little rough. We found other factors influenced it, such as flexibility and part contour. The chemically adhered surface becomes a little brittle, so high flexing can break the bond or the part. If there are sinks, that also affects it because the recommended gap for the adhesive was 0-.005 inches. There are different types of adhesives (gel-like, water-like, etc.) and also some with a rubber compound mixed in to lessen the brittle affect. The problem with the rubber compound, is it also lessens the adhesion. Hope this helps. There may be other companies with adhesives that have different properties, as we have dealt mostly with Loctite for our application.

 

[gambro]

According to the Application Technology Information from Bayer (major producer of PC = Makrolon), they recommend the following chemicals for chemical welding : Methylene chloride (=Dichloromethane)or 1,2 Dichloroethane or 1,3 Dioxalane (=1,3 Dioxethane). Before bonding, slightly dissolve the contact areas for 5-10 sec and press them together 1 hour at 5-10 bars. For even better results, dissolve 5% PC in the chemical and apply this as a thin glue film. For high strength bonds, use Methylene Chloride. For good transparency, use 1,3 Dioxolane. From a health point of view (minimizing poisonous vapors), 1,3 Dioxolane is recommended. To get rid of vapors, condition the bonded parts 50-70°C (not higher, or else bubbles will form) for 24 hours, preferably in a vacuum chamber.