Vacuum stirring defoamerThe defoaming efficiency can be improved through various aspects such as equipment parameter optimization, material pretreatment, and standardized operating procedures. The following are specific techniques, which are organized into a checklist based guide according to practical priority for easy implementation:
Optimize vacuum and stirring parameters
Vacuum gradient control: To avoid direct high vacuum causing material boiling (especially in high viscosity systems), first pump to -0.05MPa and maintain pressure for 1-2 minutes, then gradually increase to -0.095~-0.1MPa to allow bubbles to be discharged in stages.
Mixing speed matching: Low viscosity materials (such as resin solutions) are rotated at medium to high speeds (800-1200r/min) to form vortices, which drive bubbles to move towards the liquid surface; High viscosity materials (such as silicone gel and paste) should be rotated at low speeds (200-500r/min) to prevent the generation of new bubbles due to excessive shear force, while the combination of revolution and rotation modes enhances the defoaming effect.
Mixing time control: Adjust according to the viscosity of the material, generally 10-30 minutes is suitable. If the time is too long, it may cause the material to solidify or produce microbubbles due to frictional heating. The optimal time can be determined through sample testing.
Prepare materials properly
Pre dispersion and degassing: Before feeding, stir at low speed (300-500r/min) for 1-3 minutes under normal pressure to disperse the aggregated particles of the material and release some free bubbles; For materials that are prone to moisture absorption, they can be dried in an oven at 60-80 ℃ in advance to reduce bubbles caused by moisture.
Control material temperature: Increasing the temperature appropriately (such as heating resin materials to 40-60 ℃) can reduce viscosity and make it easier for bubbles to float up; But attention should be paid to the upper temperature limit to avoid chemical changes in the material.
Control the feeding amount: The loading amount of materials should not exceed 60% -70% of the capacity of the cup, and sufficient space should be reserved for the rising and bursting of gas bubbles. If the loading is too full, the materials are prone to overflow under vacuum and the bubbles are difficult to discharge.
Standardize equipment operation and maintenance
Vacuum system maintenance: Regularly check the oil level and quality of the vacuum pump, and replace it in a timely manner when the oil is emulsified or cloudy; Clean the vacuum filter and pipelines to prevent blockages that may cause insufficient vacuum and affect defoaming efficiency.
Cleaning and selection of mixing blades: Clean the residual materials on the mixing blades after each use to avoid clumping and affecting the mixing effect; Select suitable propeller types for different materials, such as anchor propellers for high viscosity materials and propeller or turbine propellers for low viscosity materials.
Sealing performance inspection: Regularly inspect the equipment sealing ring, and replace it in a timely manner if aging or damage occurs to prevent air leakage from causing unstable vacuum degree and reducing defoaming efficiency.
Auxiliary process optimization
Multiple defoaming cycles: For materials with high bubble content, a circulation process of "stirring vacuum defoaming atmospheric pressure stirring secondary vacuum defoaming" can be used to thoroughly remove deep bubbles.
Adding defoamers: Under the premise of allowing the material system, add an appropriate amount of specialized defoamers (such as organosilicon and polyether) to reduce surface tension and accelerate bubble rupture, but strictly control the amount added to avoid affecting material performance.