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The Pultrusion Process

Pultrusion is a manufacturing process for producing continuous lengths of reinforced polymer profiled shapes with constant cross-sections. Raw materials are a liquid resin mixture (containing resin, fillers and specialized additives) and flexible textile reinforcing fibers. The process involves pulling these raw materials through a heated steel forming die using a continuous pulling device.

The reinforcement materials are in continuous forms such as rolls of fiberglass mat and doffs of fiberglass roving. As the reinforcements are saturated with the resin mixture in the resin bath and pulled through the die, the gelation, or hardening, of the resin is initiated by the heat from the die and a rigid, cured profile is formed that corresponds to the shape of the die.

The key elements of the manufacturing process are:

1) Reinforcement Handling
This consists of roving creels, mat and veil dispensers, and winders or braiders where other than axial reinforcement is required.

2) Resin Impregnation
This can consist of a simple resin bath or pressure/vacuum impregnation device

3) Preforming Dies
These serve to guide the impregnated reinforcement into the correct position, remove excess resin, provide pre-compaction to the approximate profile in order to assist air removal, wetting and to reduce the pressure in the main die.

4) Pultrusion Dies
This is a machined steel or ceramic die which is heated and produced the final profile. Dies can be more than 1m in length. As the material passes though the die, heat transfer initiates the cure reaction and the pulling speed is such that the resin has fully cured by the time it leaves the die.

5) Pulling Device
By allowing a suitable gap between the die exit and the pulling device, the product cools to a stage where the resin is sufficiently hard to be gripped by the pulling device. This can be a pinch roller or a caterpillar type haul off mechanism. Pulling speeds depend upon the resin system and the size and shape of the product. Typical values from industry are in the range 0.5m/min - 1.5m/min.

6)Cut-off Device
This is a flying cut-off saw which is programmed to cut the product to the desired length.
FRP profiles: FRP gratings ,FRP tool handles, FRP cable tray,FRP railway covers,FRP antenna radomes and tubes,FRP support beams-cultivation device, and so on