RED RTV gasket maker flexibility for a particular application

Question

I have prepared a 3D printed mould made of ABS to make a gasket. I am using a RED automotive RTV gasket maker to pour into the mould. The thickness of the gasket is 3mm. And my requirement is, after tightening the screw of the both surface (between which the gasket is used to seal.) the gasket has to be "soft" or flexible enough so that the gasket can be compressed to 0.5mm thickness (from 3mm) without damaging it physically. So is that possible with red RTV gasket maker? How flexible it is after curing? Will it serve my purpose?

Answer 1

What is the purpose of the final product? If you are trying to get it to provide an air or liquid tight seal, it won't work. RTV gasket maker does several things to create its air and liquid type seals. One of those things is it creates a mechanical bond to the parts it comes into contact with. Once that mechanical bond is compromised, it quits providing the sealing action it was put there to prevent.

The other reason this won't work is because of how RTV is after it has cured. It its designed to deform (squish) into the parts on the mating surfaces so it conforms. After it cures, it loses its pliability to a great extent. While it is still flexible and can take a little bit of movement, squishing it down to 16.67% of its thickness will cause it to crack and/or break. It's just not designed to do this.

A better material to use is something like nitrile. While you can't just pour it into a mold like you're trying to do with RTV, it is very flexible and does not break when heavily deformed. It is what most modern O-rings are made out of (it used to be rubber, but rubber doesn't stand up to things like ethanol). As long as O-rings aren't damaged physically, they can be used many, many times over to provide a seal. They have a very long working lifetime.

Answer 2

You came here seeking expertise from people who work with RTV, and Paulster has shared his expertise with a good answer.

But what you have failed to realize is that your gasket conditions are impossible to achieve with any homogeneous material. What I mean by "homogeneous material" is that it is made of one substance through and through with no layers, no voids, no bubbles and no structure except a continuous solid.

There is no homogeneous material that can be compressed 6:1 (from 3mm down to 0.5mm) and still retain its shape unless you are dealing with pressures found only in stars or atomic bombs. No can do!

If your project really calls for this much compression, you have to use a material with microscopic air pockets or bubbles. Cork, which is full of air pockets, can be compressed about 2:1. Foamed polymers such as foam rubber, polyurethane foam or silicone foam and similar can be compressed 6:1 if they are so designed. Open-cell foams will leak air. Closed-cell foams are nearly air tight, especially when compressed.

I suggest you look for a 3mm closed-cell neoprene foam sheet and cut it with a razor blade or scissors. If you want a digital solution, try a Cricut machine. Neoprene foam is the material used to make diving wetsuits. If you can find neoprene foam sheets described as "low durometer" that means "softer and more compressible."