China Heat-Shrinkable Bags - Industrial Packaging Solutions from Trusted Suppliers and Factory
Core functions and how they work
Wrap the vacuum bag tightly on a mold lined with reinforced fibers (such as carbon fiber, glass fiber) and resin flow media.
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.
- 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.
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:
| Component | Functions and Materials |
|---|---|
| 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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1. 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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2. 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.
- 3. Process suitability: It has good fit and can be laid manually or automatically.
Main application industries
Manufacturing large composite components such as aircraft wings, fuselage parts, radar shields, interior panels and so on.
manufacturing wind turbine blades (this is the largest application area of the vacuum filling process).
manufacture hulls, decks, superstructures, etc., to achieve large-scale integrated molding.
body parts, chassis parts, etc. for high-performance sports cars, racing cars, and new energy vehicles.
manufactures high-performance bicycle racks, rowing boats, paddle boards, helmets, fishing rods, etc.
such as storage tanks, pipes, building reinforcing panels, etc.
