Pultrusion is a continuous process for manufacture of composite materials with constant cross-section. Reinforced fibers are pulled through a resin, possibly followed by a separate preforming system, and into a heated die, where the resin undergoes polymerization. Many resin types may be used in pultrusion including polyester, polyurethane, vinylester and epoxy.
The technology is not limited to thermosetting polymers. More recently, pultrusion has been successfully used with thermoplastic matrices such as polybutylene terephthalate (PBT) either by powder impregnation of the glass fiber or by surrounding it with sheet material of the thermoplastic matrix, which is then heated.
1 – Continuous roll of reinforced fibers/woven fiber mat
2 – Tension roller
3 – Resin bath
4 – Resin soaked fiber
5 – Die and heat source
6 – Pull mechanism
7 – Finished hardened fiber reinforced polymer
The term is a portmanteau word, combining “pull” and “extrusion”.The first pultrusion patent in the United States was issued in 1951. W. Brandt Goldsworthy is widely regarded as the inventor of pultrusion.
The design of pultrusion machines varies. Two often used types are reciprocating (hand-over-hand) and continuous (cat-track).
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