Pultruusio

Pultruusio is a continuous manufacturing process used to produce fiber-reinforced polymer (FRP) profiles with a constant cross-section, analogous to the pultrusion process known in English. It combines impregnation of reinforcing fibers with a thermosetting resin and subsequent curing in a heated die as the profile is pulled through.

In a typical pultruusio line, continuous fibers are drawn through a resin bath or resin-rich die to achieve impregnation. The impregnated fibers then enter a heated die, where the resin cures and the part assumes the desired cross-sectional shape. A take-up mechanism draws the cured profile from the die, allowing the continuous production of long lengths that are cut to size after curing.

Materials used include fiberglass, carbon fiber, and aramid fibers in thermosetting resins such as epoxy, polyester, or vinyl ester. Common cross-sections produced are rods, bars, channels, angles, tubes, and I-beams, with fiber contents typically in the range of 40 to 60 percent by volume. The process can yield smooth surface finishes and good dimensional stability, making it suitable for exterior and structural components.

Advantages of pultruusio include high strength-to-weight and stiffness-to-weight ratios, excellent resistance to corrosion and environmental degradation, and suitability for automated, high-volume production of long, straight profiles. Limitations involve tooling costs for dies and equipment, restriction to constant cross-sections, brittleness associated with some thermosetting matrices, and challenges related to end-of-life recycling of thermoset composites.

Applications span construction profiles (window and door frames, channels), electrical components (insulators and housings), transportation parts (structural rails, panels), and sporting goods such as rods and frames.