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China Heat-Shrinkable Bags Suppliers - Quality Industrial Packaging from Reliable Factory
Core functions and how they work
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Create a closed vacuum environment:Wrap the vacuum bag tightly on a mold lined with reinforced fibers (such as carbon fiber, glass fiber) and resin flow media.
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Apply uniform pressure:Air is pumped by a real air pump to create a negative pressure in the bag (usually -0.95 bar or higher). This negative pressure will generate a uniform pressure up to nearly 1 atmosphere, which will act on the workpiece.
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Resin immersion and compaction:
- Compacting fibres: Under vacuum pressure, multiple layers of fiber material are compacted to remove between layers of air to achieve the desired fiber volume content.
- Drive resin flow: Under negative pressure, the resin is inhaled from the inlet, so that it completely saturates the dry fiber-reinforced material and expels bubbles.
- Controlling resin content: The retention ratio of the resin is precisely controlled by vacuum pressure.
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Form a smooth surface:The vacuum bag is pressed against the surface of the workpiece, which can reproduce the smoothness of the mold surface (the side of the mold contacting) or form a smooth "bag surface" (the side that contacts the vacuum bag).
Main components (vacuum bag system)
A complete industrial vacuum bag system typically includes:
Vacuum bag film
The core material. It requires high ductility, high toughness, resistance to puncture and resistance to a certain temperature. Commonly used nylon (PA) film (such as PA6). For high temperature curing (such as epoxy resin above 120 ° C), high temperature polyamide or polyimide films are used.
Sealing Glue
A highly viscous, creamy sealing grease used to form airtight seals at the edges of the mold so that vacuum bag membranes can adhere to them.
De-molding cloth / isolation film
Is laid between the workpiece and the vacuum bag to prevent the resin from sticking to the vacuum bags or the flow network, facilitating de-molding. Usually porous polytetrafluoroethylene (PTFE) or silicone-coated glass cloth.
The ducting net / ducting cloth
Is laid above the workpiece to provide a fast channel for the resin to flow under the vacuum bag to ensure that the resin is uniformly soaked.
The airborne felt
Absorbs excess resin and ensures the opening of the vacuum channel so that air and volatile gases can be effectively pumped out.
Vacuum piping and joints
Include spiral pipes, fast joints, vacuum meters, and three-way valves to connect vacuum pumps to inner bags.
Vacuum pump
Provides a stable and continuous vacuum source.
Key features and requirements
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Excellent physical performance:
- High tensile strength and elongation: it can cover complex shapes of molds without rupturing and can withstand volume changes and pressure during curing.
- Anti-piercing: prevents puncture by mold edges or fibers.
- Uniform thickness: Typically the thickness is between 50-150 microns to ensure that the pressure is uniform.
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Stable chemical and thermal properties:
- Temperature resistance: must be able to withstand the highest temperature of the resin curing cycle (from room temperature to 180 ° C or higher).
- Low permeability: Very low permeability for air and volatile organic compounds to maintain a stable vacuum.
- Chemical resistance: does not react with resins or depolymerizers.
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Process suitability:It has good fit and can be laid manually or automatically.
Main application industries
- Aerospace: Manufacturing large composite components such as aircraft wings, fuselage parts, radar shields, interior panels and so on.
- Wind energy: manufacturing wind turbine blades (this is the largest application area of the vacuum filling process).
- Ship yachts: manufacture hulls, decks, superstructures, etc., to achieve large-scale integrated molding.
- Automotive industry: body parts, chassis parts, etc. for high-performance sports cars, racing cars, and new energy vehicles.
- Sports equipment: manufactures high-performance bicycle racks, rowing boats, paddle boards, helmets, fishing rods, etc.
- Industrial products: such as storage tanks, pipes, building reinforcing panels, etc.
Frequently Asked Questions (FAQ)
How does a vacuum bag system apply pressure to the workpiece?
By pumping out the air using a vacuum pump, a negative pressure (typically -0.95 bar or higher) is created inside the sealed bag. This negative pressure causes atmospheric pressure (up to nearly 1 atmosphere) to press uniformly against the entire surface of the workpiece.
What are the primary materials used for vacuum bag films?
Nylon (PA) films, such as PA6, are commonly used for standard processes. For high-temperature curing environments (such as epoxy resins cured above 120°C), specialized high-temperature polyamide or polyimide films are preferred.
Why is a de-molding cloth or isolation film necessary?
It is placed between the composite workpiece and the vacuum bag to prevent the curing resin from sticking directly to the vacuum bags or flow networks, which ensures easy and damage-free de-molding after the curing process is complete.
What physical properties must a high-quality vacuum bag film possess?
A high-quality vacuum bag film must have high tensile strength and elongation to fit complex mold geometries without tearing, excellent puncture resistance to prevent leaks from sharp fiber ends, and a uniform thickness (usually 50-150 microns) for even pressure distribution.
What is the role of the airborne felt in the system?
The airborne felt acts as an absorbent layer for excess resin while maintaining an open path for air and volatile gases to be continuously and effectively evacuated from the bag during the process.