Self Adhesive Specification

[drawoh]

We have ordered and received some silicone rubber self adhesive pads. These were installed on aluminium frames, and they have all fallen off. Apparently silicone rubber is difficult to stick to. but we did order self-adhesive. I now have a sample of new pads from the vendor which I am about to test.

Question: Assuming they work, I need to update my drawings to show some sort of performance specification that will allow us to pass or fail rubber pads. I want to show something like "will be installed with a roller with 15-20N applied force. System will be mounted upside down for 24hrs".

Any thoughts?

--
JHG

 

[MintJulep]

Aluminum is difficult to stick to too. thread728-337362

Quantify load magnitude and direction relative to the adhesive, and adhesive area.

For example "Must demonstrate tensile bond strength of 234 psi for 24 hours"

 

[Compositepro]

When the pads fell off, did the adhesive stay with the pads or the aluminum? Those are two completely different problems. I suspect that the adhesive was still on the silicone, and therefore, the observation that silicone is difficult to stick to is a red-herring. In any case, pressure sensitive adhesives (psa) will not hold-up against constant low level tensile or peel loads, like those caused by gravity. Get some rubber pads that can be mechanically attached. Leveling feet seem appropriate.

 

[drawoh]

Compositepro,

The adhesive stuck very well to the aluminium. Silicone is a low surface energy material, and it responds very well to different adhesives. RTV silicone works very well. The new stuff looks good so far.

3M 9731 two-sided tape sticks silicone rubber to aluminium. I made a point of doing a sloppy job of installing it, and it worked. Whatever I do must work in production. If they clean the aluminium with alcohol, things should be that much better.

I clicked on MintJulep's link. Blakmax's comments about Alodine finishes are interesting.

--
JHG

 

[Compositepro]

Silicone is often used as a non-stick surface, but in the right process it can be bonded very well. Let relate and anecdote.
I sealed a silicone tube to a disposable part using silicone RTV in a 400F application. After curing the silicone at room temp overnight and going through a heat cycle, the sealant was complete fused to the tube and could not be removed from the tubing without destroying it. I cut-off that part of the tube and used it again through another cycle with fresh sealant. This time the sealant could be removed from the tubing. The issue was that the silicone tubing had not been completely cured by the manufacturer.

Oh, and by the way silicone RTV is a crosslinked thermoset polymer. It is not a pressure sensitive adhesive and it cures slowly. I have used psa's to fixture parts while silicone RTV cures.