Q & A: Platinum Cured Silicone Rubber (19 comments)

My platinum cured silicone rubber is set too fast, how to longer its working hour? What type of additive to be added? Thank you.

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Platinum-cured silicone is a type of room temperature vulcanized silicone, so the curing speed is greatly affected by temperature. You can lower the temperature of the operating environment to extend the operating time. In addition, when purchasing silicone raw materials, you can customize silicone with a longer operating time from the silicone manufacturer. Of course, you can also add a special slow-drying agent for silicone to extend the operating time.

I have some high strength platinum cure silicone that I use to make soft plastic molds and decided to try using it to make leads. I made 2 molds for 2 different lures and I poured 100 times through each mold and they are both in great shape with no signs of wear and I feel like I could pour hundreds more. I must mention that I poured out the lead first and then let the mold cool to room temperature before pouring it out.

Can I pour low melting point metals into platinum-curing silicone molds?

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Sure. Platinum-cured silicone can withstand temperatures up to 250°C, but it is not recommended for use with materials exceeding this temperature. To provide optimal mold life and the best detail reproduction when pouring low-melting-point metals into the mold, it is highly recommended to preheat the silicone mold in an oven to a similar temperature before pouring the molten metal into it. This can prevent the metal from solidifying immediately upon contact with the cold mold and prevent rapid skin formation. Therefore, preheating the platinum-cured silicone mold enables more consistent castings and longer mold life.

What materials should I avoid to avoid inhibiting the curing process of platinum-cured silicone?

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Yes, to prevent inhibition of the curing process of platinum-cured silicone, it is necessary to avoid materials containing sulfur, tin compounds, PVC, certain types of rubber, and amines. Sulfur is the primary substance that inhibits the curing of platinum-cured silicone. It can be found in natural rubber, water-based and oil-based clays not labeled as "sulfur-free," and in latex gloves. Additionally, ensure that your workspace and tools are clean and free of potential contaminants that could affect the curing process. Once the silicone mold is fully cured, it is completely unaffected by these materials and can be used in casting processes without concern.

I tried using a resin print cast to make the silicone mold, but ended up with sticky silicone that wasn't fully cured where it touched the model. I used addition cure silicone 1:1 and I brushed the model with Vaseline as a release agent before molding so I'm not sure if it reacted with the resin, isopropyl alcohol or Vaseline.

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Platinum-cured silicone is not compatible with 3D printer resins. To do this, you will need to prime the model with an acrylic primer, making sure that none of the resin comes into contact with the silicone. Or use tin-cured silicone.

When I was making silicone molds for the dice, I discovered that the 3D printing resin master would cause a chemical reaction and prevent the liquid silicone from curing, leaving a thin sticky layer around the dice when separated after curing. This silicone also does not appear to cure when placed with certain epoxies, glues, and other plastics.

It seems that curing is a common problem with platinum-cure silicones. No matter how long I left it, the tacky part never fully cured. I tried solving this problem by pouring multiple layers and letting them cure before adding more layers, this strategy didn't work.

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Yes, the platinum catalyst in platinum-cure silicone is easily contaminated by acids, alkali, sulfur and other substances and cannot be cured. Therefore, please check the material composition of your master mold.

I love this stuff, it's 1:1 ratio, I use a food scale to measure the ratio. It has no smell and is easy to clean. I used a recycled plastic knife to stir because the solution is oily so it's easy to wipe off with a paper towel for reuse.

It blends easily without any problems. To see if Part A and Part B were evenly mixed, I added the silicone pigment and stirred them together. They can withstand resins with high thermal reactivity when cast in small quantities.

I love the translucent cure effect and it's perfect for UV resin molds. It mixes easily with mica pigments. But the 10A silicone I'm using now is too soft and easily deforms. I need harder silicone.