Core factors that determine the suitability of casting silicone
1. Hardness (Shore A)
Low hardness (10-30A): Excellent elasticity, suitable for replicating models with rich details (such as reliefs and patterns), but weak tear resistance, and frequent demolding should be avoided.
Medium hardness (40-60A): Taking into account both elasticity and strength, it is suitable for most casting scenarios (such as resin ornaments, cement component molds).
High hardness (70-90A): The hardness is close to that of plastic, suitable for molds that require support (such as large castings), but the flexibility is poor, and attention should be paid to demolding design.
2. Temperature resistance
Short-term temperature resistance: Ordinary RTV silicone can withstand 150-200℃, and HTV silicone can withstand 200-300℃. It needs to be selected according to the curing temperature of the casting material (such as HTV for metal casting and RTV for resin casting).
Long-term temperature resistance: If the mold needs to be used repeatedly, it is necessary to ensure that the silicone does not age or deform under long-term high temperature (such as HTV is more suitable for high-frequency and high-temperature conditions).
3. Tear strength (≥12N/mm)
The higher the index, the more durable the mold, especially suitable for castings with complex structures (such as multi-angle and deep groove models) to avoid tearing during demolding.
4. Fluidity and curing time
Fluidity: Low-viscosity silicone (such as injection grade) is suitable for automated casting machines and can quickly fill small molds; high-viscosity silicone is suitable for manual scraping to avoid flowing.
Curing time:
Fast curing (10-30 minutes): suitable for mass production, but may cause distortion of details due to exothermic reaction;
Slow curing (2-24 hours): suitable for fine models, more uniform curing, but low efficiency.
5. Shrinkage rate (≤0.5%)
The lower the shrinkage rate, the higher the casting precision. Low-shrinkage silicone (such as addition-type silicone shrinkage <0.1%) should be selected for precision parts casting.
