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What post-processing processes are typically required for silicone products after molding?
2025-03-31
Molded silicone rubber products typically require a series of post-processing operations after molding to enhance product performance, improve appearance, or meet specific functional requirements. The following are common post-molding processes and detailed descriptions:
1. Burr removal (deburring/trimming)
Reason: Flash or burrs are generated at the overflow or parting line during molding.
Methods:
Manual trimming: Manually remove burrs using scissors, blades, or special tools; suitable for small batches or precision products.
Cryogenic deburring: Freeze the product (e.g., below -30°C) to make the silicone brittle, and remove burrs through vibration or sandblasting; suitable for complex shapes or mass production.
Mechanical punching: Use stamping dies or automated equipment to remove burrs in batches; high efficiency but requires custom tooling.
Precautions: Avoid excessive trimming that could damage the product or cause dimensional deviations.
2. Secondary vulcanization (post-curing)
Purpose: Remove residual volatiles, increase silicone crosslinking density, and enhance mechanical properties and temperature resistance.
Process parameters:
Temperature: 180-200°C (adjust according to silicone type).
Time: 2-4 hours.
Equipment: Oven or vulcanization tank; requires uniform temperature control.
Effect: Reduce odor, improve tensile strength, rebound resilience, and chemical stability.
3. Surface treatment
Spraying/coating:
Functional coating: Spray anti-static, hydrophobic, or flame-retardant coatings.
Decorative coating: Add color or matte/glossy effects; requires the use of silicone-specific inks.
Screen printing: Print logos, text, or patterns; requires adhesion testing.
Laser engraving: Precise engraving of markings or textures; non-contact processing, suitable for high-precision requirements.
Plasma treatment: Increase surface energy, enhance bonding or printing adhesion.
4. Cleaning and inspection
Cleaning:
Ultrasonic cleaning: Remove surface dust or release agent residue.
Solvent wiping: Clean with solvents such as isopropyl alcohol.
Inspection:
Visual inspection: No bubbles, missing rubber, stains, or burrs.
Dimensional inspection: Calipers, projector, or three-coordinate measurement.
Performance testing: Hardness (Shore A), tensile strength, tear strength, aging resistance, etc.
5. Special post-processing
Bonding and assembly:
Silicone rubber bonding to metal/plastic: Use primer to enhance bonding strength, in combination with silicone adhesive (such as RTV glue).
Mechanical fastening: Embed metal parts or screws.
Functional modification:
Conductive treatment: Add conductive fillers or plating.
Antibacterial treatment: Add antibacterial agents or surface coatings.
6. Packaging and storage
Dust-proof packaging: Avoid silicone rubber adsorbing dust.
Anti-sticking treatment: Sheet products need to be placed in layers to prevent sticking.
Environmental requirements: Avoid light and moisture; the recommended storage temperature is 10-25°C.
Key Precautions
Process sequence: Typically deburring → cleaning → secondary vulcanization → surface treatment → inspection.
Temperature control: Secondary vulcanization requires slow heating/cooling to avoid deformation due to thermal stress.
Environmental requirements: Some processes (such as solvent cleaning) must comply with VOC emission standards.
By rationally selecting post-processing processes, the quality and added value of molded silicone rubber products can be significantly improved to meet the stringent requirements of medical, electronic, and automotive fields. In practical applications, the process needs to be comprehensively optimized based on product use and cost.
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