What are prepregs?
The term "prepreg" is actually an abbreviation for the phrase pre-impregnated. A prepreg is an FRP reinforcement that is pre-impregnated with a resin. Most often, the resin is an epoxy resin, however other types of resins can be used, including the majority of thermoset and thermoplastic resins. Although both are technically prepregs, thermoset and thermoplastic prepregs are dramatically different.

Thermoset Prepregs:

More commonly used prepregtype in composite manufacturing is thermoset prepregs. The primary resin matrix used is epoxy. However, other thermoset resins are made into prepregs including BMI and phenolic resins.
With a thermoset prepreg, the thermosetting resin starts as a liquid and fully impregnates the fiber reinforcement. Excess resin is precisely removed from the reinforcement. Meanwhile, the epoxy resin is undergoes a partial curing, changing the state of the resin from a liquid to a solid. This is known as the "B-stage."

SPM is a company specialized in manufacturing thermoset epoxy prepregs.
Advantages of Prepregs
- Ease of use
- Low void content
- Control of fibre volume fraction
- Control of laminate thickness
- Lower labour cost
- Better quality and conformity
- Clean process
Processing Techniques
- Vacuum bag moulding (oven cure, Out of Autoclave)
- Re-usable vacuum bag moulding
- Autoclave moulding
- Press moulding
- Pressure bag moulding
- Thermal expansion moulding
- Tube rolling
Storage and Safety
Prepregs should be stored, wrapped and sealed in polythene at -18°C for maximum shelf life. The material must be fully thawed before breaking the polythene seal in order to avoid moisture contamination.

Prepregs are low risk in terms of handling hazards, however the usual precautions should be applied.

Gloves and protective clothing should be worn. Use mechanical exhaust ventilation when heat curing prepreg systems. Please see the material safety data sheets for the related products.