Pultrusion Basics

     Pultrusion is a manufacturing process for producing continuous lengths of FRP structural shapes with constant cross-sections. Raw materials used in pultrusion include a liquid resin formulation, flexible textile reinforcing fibers and a polymer surfacing veil. In general, the pultrusion 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 continuous filament mats (CFM) or doffs (hollow spools) of fiberglass roving.

    As the reinforcements are saturated with the resin mixture in a resin bath (“wet-out”), they are shaped by a preformer and pulled through a heated die. The cure of the resin is initiated by the heat from the die, setting off a catalytic reaction that results in a rigid, cured profile corresponding to the shape of the die cavity.