Pultrusion
From Plastics Wiki, free encyclopedia
Pultrusion Pulling glass fibers through a resin bath to make continuous profiles, pipes and other shapes. This process is similar to profile extrusion, but it does not provide flexibility and uniformity of product control, and automation. Used for continuous production of simple shapes (rods, tubes, and angles) principally incorporating fiberglass or other reinforcement. High output possible.
Process
The process starts when reinforcing fibres are pulled from the creel: the reinforcements, are guided towards the impregnation station passing through a preforming station where rovings and mats are carefully guided in successive steps; the impregnation of all filaments of each roving and mat occurs as they pass through the bath containing the resin formulation.
The composite material then enters a heated steel die that has been precision-machined to the final shape of the profile to be produced. While the material is being pulled through the die, the heat initiates an exothermic reaction in the thermosetting resin matrix.
Finally, a GRP profile, fully cured and with its final cross-sectional dimensions, exits the pultrusion die; the pulling mechanism can either be a caterpillar-type puller or two reciprocating clamps to ensure continuous movement.
Finally, the profile is cut to the desired length by an automating flying cut-off saw.
Due to its nature of continuous process, the pultrusion is arranged on three shifts and is particularly suitable for a mass production.
Advantages
- Structural properties of laminates are greatly improved
- Resin impregnation area can be enclosed limiting volatile emissions
- High glass content can be achieved
Disadvantages
- Profile with complex cross section difficult to pultrude
- High initial investment
- Uniform cross section profiles only feasible
