Bonding Duroid to aluminum using RTV

[chopper75]

I am trying to bond a piece of Duroid sheet to an aluminum surface. The Duroid is forced to a curved surface on the aluminum. I am pressing the Duroid sheet to match the aluminum's curved surface. It is being bonded with RTV (Momentive RTV88) and RTV Primer (Momentive SS4004P). After the 24 hour cure, we are seeing some delamination. I am looking for some ideas on how to correct the issue.

 

[btrueblood]

Duroid = PTFE, i.e. Teflon, with some reinforcement fibers. Without etching with some fairly nasty stuff (that would likely ruin the reinforcement fibers) you aren't going to be able to bond anything to teflon. You might get the stiction of the RTV to do what you want if you preform the sheet to match the surface profile. But it won't hold up for long, or across many thermal cycles. Mechanical fasteners are the way forward, in my opinion.

 

[chopper75]

btrueblood, thank you for your reply. The Duroid actually is etched. Sadly, we have no control on the design so we must use the RTV somehow...

I like the preforming idea. I wonder if pre-heating the duroid may help it retain some shape memory?

 

[btrueblood]

Ok, that helps. Yes to preheating. Teflon gets soft at about 350-400 deg. F. You could machine a plate from steel, to match the profile you want, clamp the sheet to the plate, and bake it for a few hours in a conventional oven. You might want to compensate for thermal expansion (well, contraction in this case) of the sheet when it cools, if you need to match a fairly complex profile.