Rubber/Silicon Material for Watches

Hi all,

I was wondering of someone could give me some more info related to the materials used for full-body rubber/silicon watches such as these ones: or
The last one referes the metarial as “silicon”. I can imagine there are different types of "rubber"and “silicon” so i was wondering if any of you has more specific name to give in relation to these materials used in watch/accessory making.
Thank you very much for any information.

The watches you linked to appear to be molded silicon. There are variations of the material but in general it provides a heat resistant, mold/mildew resistant, food-safe skin and can be molded thicker than plastics without sinks, overmolded without damaging substrates, etc. It tends to surface heal itself when molded, so you get super-smooth bubble free surfaces.

There are thousands of rubber formulations, some natural, some chemical, lots of combinations (natural, chloroprene, butyl, etc) but almost none of those can provide the tactile feel with the surface safety of silicon. We’re currently working with TPU rubber as it is one of the few rubber-like formulations that can obtain FDA approval, but we’d have rather used silicon if it would have been feasible for our particular design.

You can spec silicon [silicone] and most tooling houses and/or plant engineers will help you choose the right formulation for your application.

I’m going to disagree with this.

The tool for silicone is significantly different from a tool for a thermoplastic. You cannot run a thermoplastic in a silicone tool and you cannot run silicone in a thermoplastic tool.

So “most” tooling houses are geared for thermoplastics and don’t make silicone tools. Silicone is somewhat specialized and there are not a lot out there when compared to thermoplastics.

For silicones, I have used Rogan with great satisfaction. YMMV.

I think what iab is getting at is that you require a facility capable of liquid injection molding as silicone is a thermoset elastomer (as opposed to thermoplastic). Shops that do liquid injection molding usually do urethane rubbers and other thermoset elastomers as well

Sorry iab, we use shops that know both. My point was also that spec’ing the material formulation does not have to be the burden of the designer, as plant based engineers and knowledgeable tool houses have better experience with it.

There we are in full agreement. The vender is typically the best resource for specifying the exact material. The designer or engineer needs to only specify the desired/required material properties. I haven’t a clue to specifically which will fulfill my needs.

fwiw, Rogan also does both. (I know I sound like a shill, but I have no vested interest in their business other than they have made some good parts for me.)

Also, another nice feature of silicone molding, it handles variable wall thicknesses beautifully. Minimal to no seam lines and no freezing off. Expensive due to cycle times, but managable.

Hi all, thansk for the information you all provided… the discussion was rather informative.

Generatewhatsnext, you mention TPU. In my previous job we used TPR for the softer parts on stationary products (just to feel a bit more user friendly and provide better grip oposed to ABS) but TPR after some time was becoming super sticky,very dirty and its color would change. TPU i guess belongs to the same family of materials with TPR, so do you have any experience if it is more durable?

Thanks again all for your input.

In our current application we’re using customized sheets of TPU enclosed within a potable-water [sanitary] environment, so its surface feel will never be an issue, only it’s continued chemical safety (hence the FDA approval being so important). In this case, we needed a material that will pass NSF61 so TPU won the job.

We’ve used TPR as an alternative to other elastomers for its user benefits and we’ve seen some of those materials become sticky, but I think that’s more of a poor plant formulation choice than a material characteristic. That’s my guess because plenty of our past products still have intact TPR - I’m looking at a 16 year old product I designed that still has awesome TPR over molded handles, so the material works when properly spec’d and formulated.

We have a great ‘materials’ oriented engineer with a doctorate in this ‘stuff’ that helps guide our material spec’s process. When I don’t know something (which is very often :slight_smile: ) he undoubtedly does!

Hope that helps.

Generatewhatsnext, your experience helps a lot on how to deal with our material selection and negotiations with the ours & vendor’s engineers. Thanks a lot!

Happy to be of help.

i think the swiss watches glass is usually made of sypher material usually a silicon material which is scratch less. i would suggest you to visit some of their industry, have their suggestion it would be advantageous for you