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Overcoming the Challenge of Making RTV Silicone Molds

by Nice Rapid | Sep 30,2022 | Silicone Molding

Have you considered RTV silicone mold rubber at some point? If you haven't, you should, since making efficient molds is becoming the latest trend. The procedure offers many benefits, such as thermal resistance, long-lasting flexibility, and the possibility to bond, seal, pot, or encapsulate your parts. You can also apply coating if you want a clean finish. Mold making is an art, and there's a road to perfection to achieve a good product. The following are some of the challenges you can face and how to overcome them:

Cure Inhibition

As the name implies, cure inhibition is when your products don't curate properly inside the mold, this can happen due to some factors we're listing here:

You're using Polyaddition RTV Silicone

If the silicone it's not curing correctly, something went wrong when you made the mix for the mold. Ionization requires the use of platinum, and this agent can get easily contaminated if the mold is made poorly. The worst part is that there's no fixing these issues. You will have to create a brand-new mold from scratch using the right mix of components.

RTV silicone products

You get composite prepreg

The first few batches of products may look good, but their structure is compromised. You must handle the model for the mold with latex gloves and ensure the working area is pristine. Using a clean poly film is the best way to prevent the presence of composite particles that damage the build. If you apply silicone rubber over a contaminated model, you're running the mold on purpose, leading to inhibition.

You didn't run a patch test

When building anything using a mold, you must ensure all materials are compatible with polyaddition (platinum) to cure silicone rubber. You can do so with a quick patch test in a non-essential section of the master sculpt to ensure inhibition goes through. You're good to go if you see the silicone settling down and appropriately cured.

You work with Polycondensation-Cured Silicones

If your workshop handles polycondensation- (tin) cured silicones and addition- (platinum) cured silicones, you first have to store these components separately. Yes, both are silicone resins, but their chemistry is unique, and they cancel each other, even by air particles. Ensure your storage system keeps both materials in separate spaces and handles them with distinct sets of tools.

Dealing with air bubbles

Way too many manufacturers handle the mix of polymers by hand. For silicone rubber mold, it's best to use static mixers and keep the viscosity rate at 5000 CPS for at least 10 minutes. This should be done in a vacuum chamber using a large spatula or a drill packaged with mixer blades. By going this route, you can eliminate the undesired air bubbles that compromise the integrity of your parts and make your mold unusable.

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