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Vacuum Bagging for Composites

High Tech Composite Parts for Defence, Boats, Aerospace, Racecars, Windmills, Trains, etc.

Vacuum bagging which has replaced traditional hand layup methods, is a process used in Vacuum Infusion Technology. Vacuum bags are usually made from Plastic film. However now modern companies have changed to Permanent Silicone vacuum bags, custom made to the shape of the part, which can be used for a number of vacuum cycles. These bags are more expensive than plastic film, but in the right production situation can readily pay for themselves.


Normally the thickness of the Silicone bag must be at least 8 to 10 mm, but with Fortisil Silicones, thickness of 3-4 mm is sufficient. With 3mm thickness the porosity of the Silicone bag allows the Styrene solvent to go through the membrane and increases the life of the bag.

Silicone Vacuum Bags are most effective and mainly used in case you have to make a minimum of 30-40 pieces of the same object

Advantages of Vacuum Bagging over Conventional Hand Layup or Clamping Techniques:


  • Even Clamping Pressure

  • Control of Resin Content

  • Custom Shapes

  • Efficient Laminating

  • Accurate control of part thickness

Advantages of Silicone Vacuum Bags over Plastic Film:


  • Reduced tooling costs

  • Higher fibre to resin ratio

  • Faster production times

  • Less labour usage

  • Little to no plastic waste

  • Lower resin usage

  • Cost-Effective

  • Reusable

  • Used for production of negative draft parts

  • Operates at high temperatures up to 200 °C

  • Wrinkle free surface

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