Liquid silicone bubble removal is an important step to ensure the quality of silicone products. Here are some effective methods for liquid silicone bubble removal:
1. Natural bubble removal method
Reduce the addition of curing agent: For condensed liquid silicone, the operation time can be extended by reducing the amount of curing agent added, thereby achieving the effect of natural bubble removal. This method is suitable for small-scale experimental production, but it should be noted that the curing time may be extended accordingly.
Reduce the operating temperature: Under the condition of the same amount of curing agent added, lowering the temperature of the operating space can extend the curing time and make it easier for bubbles to be discharged naturally. This method is also suitable for small-scale production.
2. Stirring skills
Stirring in the same direction: When stirring liquid silicone, try to keep stirring in the same direction, which can reduce the generation of bubbles. Stirring should be gentle to avoid violent stirring to introduce more bubbles.
3. Adjustment of silicone viscosity
Reduce viscosity: Manufacturers are required to reduce the viscosity of silicone during production to increase its fluidity, so that bubbles are easier to discharge. However, it should be noted that too low viscosity may affect the performance of silicone products, so it is necessary to weigh the pros and cons and make adjustments.
4. Vacuum defoaming method
Vacuum machine defoaming: This is the most effective and commonly used method for liquid silicone to remove bubbles. By placing liquid silicone in a vacuum defoaming device, the bubbles are quickly broken and the gas is released by reducing the air pressure. The vacuum defoaming equipment can ensure that bubbles can be effectively removed regardless of the viscosity of the silicone. This method is suitable for mass production and can significantly improve product quality.
Operation steps: First, inject liquid silicone into the mold or container; then, place the mold or container into the vacuum defoaming equipment and turn on the vacuum pump; finally, observe the bubbles in the silicone gradually disappear. When the vacuum meter reaches a certain negative pressure value (such as -0.1Mpa), turn off the vacuum pump and power supply, and slowly open the vent valve to complete the defoaming process.
5. Other methods
Low-temperature baking: If the silicone raw material contains volatile impurities, these impurities may vaporize and form bubbles when heated and cured. At this time, low-temperature baking can be adopted to volatilize the impurities first, and then increase the temperature for curing. However, it is necessary to control the baking temperature and time to avoid damaging the silicone products.
Place at room temperature: For silicone with a thinner viscosity, you can stir it evenly and place it at room temperature for a period of time (such as 2-4 hours) to allow the bubbles to float up and be discharged. However, this method has limited effect on silicone with a higher viscosity.