Medium Hardness Platinum Cured Silicone Rubber for Mold Making

Step 1: Model Preparation

The master pattern should be thoroughly cleaned and dried. If the master model is fragile, weak, or porous, it may be necessary to apply a consolidant or sealant, and possibly fill in deep holes or crevices.

Step 2: Applying Release Agent

This series of silicones is highly regarded for its exceptional demolding performance, making the use of a demolding agent unnecessary for most materials. However, in cases where the master pattern exhibits high porosity, a rough texture, numerous cracks and undercuts, or is difficult to demold, it is advisable to apply a thin layer of demolding agent. This not only facilitates the demolding process by reducing friction and adhesion but also helps to extend the lifespan of the mold.

Commonly used demolding agents include acrylic spray, Vaseline, silicone oil, and soapy water, among others. These agents provide effective release properties, allowing for easier removal of the molded object from the mold.

Step 3: Measuring & Mixing

Mix the desired amount of Parts A and B in a 1:1 (by volume or weight) ratio and thoroughly mix them together. Accurate measurement is essential to achieve the best physical properties of the cured rubber. If you wish to add color to the silicone material, incorporate the desired colorant into the mixture. Mix the colorant thoroughly to achieve a uniform color throughout the material.

Step 4: Vacuum Degassing

You can assess the need for vacuum degassing based on the specific requirements of each project, but it is still recommended for achieving a flawless finish. If using vacuum degassing, place the mixed silicone in a container that is 3-4 times larger than the volume of the liquid silicone and vacuum degas until the silicone rises and then collapses. Continue vacuum degassing for an additional 1 to 2 minutes.

Techniques to Reduce Air Bubbles:

1. Hold the silicone container high above the master pattern and allow it to flow down slowly in a thin stream. This helps to break up any air bubbles as the silicone flows.
2. Temporarily incline the master pattern at an angle and pour the liquid silicone onto the higher end, allowing it to flow down over the rest of the pattern. Once the silicone reaches the lower end, lay the pattern flat and/or tilt or rotate it as necessary to achieve even coverage.

These techniques can be used alone or in combination with each other. Additionally, reducing the temperature and decreasing the ratio of curing agent can extend the working time and help to reduce air bubbles.

Step 5: Pouring Silicone

Pour the liquid silicone as soon as possible after mixing or vacuuming to achieve the best flow and air bubble release. The liquid silicone material should be poured at a depth of at least 0.5 cm above the highest point of the model surface. If the layer is too thin, the mold can tear easily.

Step 6: Demolding the Mold

Under normal circumstances, platinum-cure silicone rubber cures within the specified demold time at room temperature (25℃/77°F). Higher temperatures will result in shorter curing times, while lower temperatures may require more time for curing to complete.

After the specified curing time has elapsed, the outer surface of the mold should feel hard and dry. If the mold's hardness does not change after a period of time, it is usually safe to remove or demolded.