Reducing the shrinkage rate of silicone molds has long been a challenge for many mold manufacturers, as it can result in inconsistent product dimensions. However, this problem is not insurmountable, and there are techniques available to minimize the shrinkage rate of silicone molds. This article explores the methods for reducing silicone mold shrinkage.
Silicone rubber, as an elastomeric material, inevitably undergoes shrinkage. However, when compared to many other elastomeric materials, silicone exhibits relatively low shrinkage rates. For instance, tin-cure silicone typically has a shrinkage rate of approximately 0.3% to 0.5%, while platinum-cure silicone can have a shrinkage rate as low as 0.1% to 0.2%. This relatively low shrinkage rate makes silicone a commonly used material in the mold-making process, as it contributes to maintaining the relative stability of product dimensions.
silicone mold
Here are some practical techniques for reducing the shrinkage rate of silicone molds:
1. Selecting the Appropriate Silicone Material
Different types of silicone materials have varying shrinkage rates. In general, platinum-cure silicone exhibits lower shrinkage rates compared to tin-cure silicone, and high-hardness silicone has relatively smaller shrinkage rates than low-hardness silicone.
2. Accurate Measurement and Mixing
If using tin cure silicone, ensure precise control of the curing agent proportion, keeping it below 4%. Excessive curing agent can result in increased shrinkage.
3. Proper Mold Storage
The shrinkage rate of silicone molds gradually increases over time, as it is an inherent property of silicone. It is advisable to store molds by placing the master model inside the silicone mold and storing it in a cool place, away from high temperatures and sunlight.
4. Maintain Molds Properly
When using silicone molds for casting heat-releasing materials, it is essential to promptly demold the product after curing. This is particularly crucial because certain materials, such as polyurethane resins, release a significant amount of heat during the curing process, which can potentially damage the mold.
5. Control Silicone Curing Temperature
When making molds, try to cure rtv-2 liquid silicone at room temperature (20-30°C) to reduce mold shrinkage, as high temperatures can result in more significant shrinkage. If heating is necessary for curing, use gentle heating (40-50°C).
6. Supplementary Techniques
The larger the product dimensions, the more noticeable the shrinkage. When creating larger products, consider incorporating a layer of fiberglass cloth in the mold to help reduce shrinkage.
By implementing these methods in combination, you can effectively reduce the shrinkage rate of silicone molds, leading to more stable product dimensions.
