BLADDERS FOR THE COMPOSITES INDUSTRY

What is bladder moulding?

Aluminium dip-coating mould

Natural High-Temperature latex bladder

Bladder moulding involves the use of an inflatable object (bladder) inside a cavity (female mould), conferring compression and compaction of the layers of composite material during curing of the parts.

1. Place pre-impregnated sheets in the desired orientation inside the female mould
2. Position the bladder above the layers of carbon
3. Place the second layer of carbon on top of the bladder, or in another part of the mould and close the mould.

4. Inflate the bladder and heat the mould to the pre-impregnated sheets' cross-linking temperature.
5. Once curing is complete, deflate and remove the bladder, open the mould and strip the part.

Advantages of using our High-Temperature latex bladders

Precise control of outer diameter, the object being moulded against the walls of an internal matrix.
Few hollow spaces, excellent finish
Smooth inner diameter, no bladder creases
High pressure, up to 300 psi, without the need for an autoclave.
Short curing cycles, the mould can be preheated prior to assembly
The bladder can be removed after curing for possible reuse
Few geometric constraints
Cheap latex and mass production moulding possible
Good results and reasonable prices can be achieved for non-complex tools.

Moulding options for hollow parts

Autoclave
Compression moulding
Extrusion
Filament winding
Bladder moulding
Resin transfer moulding (RTM)

Advantages of bladder moulding

Bladder moulding gives highly consolidated laminates with variable shape, cross-section and thickness.
Moreover, though the moulds are subjected to internal pressures of between 3 and 20 kg/cm² (50 to 300 psi), the tooling and equipment used can be relatively simple compared to other moulding options.

Latex bladder selection

Curing conditions - time and temperature
Mould size and shape
Bladder thickness
Compatibility with the resin system

Curing conditions

Time and temperature are interdependent. PIERCAN USA, INC. has formulated its latex for enhanced resistance to temperatures of between 120 and 175°C (250-350°F).
Experience has shown that our bladders are able to withstand between from 25 to 30 hours at 125°C (250°F) and one hour at 175°C (350°C). These conditions are acceptable for the majority of composite applications.

Mould size and shape

Mould shape is important. It should be remembered that the bladders will inflate, requiring considerations of where the air will arrive in the bladder and how this latter is extracted from the part at the end of the process.
Size is important to determine costs and compatibility with our current production equipment.

Bladder thickness

The standard thickness of our latex bladders is of 0.6 to 0.8 mm. In certain cases, we can make bladders between 0.8 and 1.0 mm in thickness, though the standard thickness is suitable for 90% of our customers' applications.

Compatibility with the resin system

Compatibility with the resin system is difficult to predict, though a simple test is better than a large-scale analysis. In general, latex works with most epoxy and polyester resin systems. The bladder is easy to remove.