The Pultrusion Process

Strongwell’s core competency is pultrusion!  We have done it longer and better than anyone else in the world, and today we produce tens of thousands of feet of structural fiberglass pultruded parts every hour!  This section gives a very brief description of the pultrusion process.

The Process

Pultrusion is a manufacturing process for producing continuous lengths of reinforced polymer structural 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 (rather than pushing, as is the case in extrusion) 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 (“wet-out”) 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.
While pultrusion machine design varies with part geometry, the basic pultrusion process concept is described in the schematic shown below.

Pultrusion_Process