Pultrusion

Developed in the 1950's by the person considered by many to be the father of composites, W. Brant Goldsworthy, pultrusion is the process of pulling raw composites through a heated die creating a continuous composite profile. The term pultrusion combines the words, pull and extrusion. Extrusion is the pushing of material, such as a billet of aluminium, through a shaped die. Pultrusion, is the pulling of material, such as Basfiber® and resin, through a shaped die.

Pultrusion Application Process
Layers
Basalt Fiber Tech Pultrusion Application Process©2015 - Designed by Lucas Sant'Anna
  • 1Basfiber® Rovings are placed in position to receive the resin equally. The selected Tex of the roving depend on the proprieties that the final product require.
  • 2 Alignment machine can be used to put the Basfiber® Rovings and reinforcement material in the correct position to receive the resin. The layers are positioned according to the strength and flexibility needed for the final material.
  • 3 Reinforcing Material can be added to enhance the desired proprieties of the final product. The reinforcing material can be Basfiber® Fabrics, Carbon or Aramid.
  • 4 The Resin Impregnation Chamber distributes the resin equally to the material, assuring that the Basfiber® will impregnate the resin within the reinforcing material while it heats to the temperature needed to the next moulding phase.
  • 5 The Moulding phase is when the composite already impregnated and heated gets the form of the desired material applying pressure and curing the material with a low temperature application.
  • 6 The Rolling machine pulls the composite through the mould reducing its temperature until its get cold/rigid enough to cut. This is a continuous production process from the roving to final composite.
  • 7 The Cutting Machine cuts the final cured composite to the size which specified. After this phase the final product is ready, requiring only the finishing glaze and varnish.
  • 8 Final Product is a fiber-resin composite material that can be produced in line, in large scale and for low cost.

The pultrusion process starts with racks or creels holding rolls of Basfiber® Non-Woven or Basfiber® Fabrics of Basfiber® Roving. Most often the reinforcement is fiberglass, but it can be carbon, aramid, or a mixture. This raw fiber is pulled off the racks and guided through a resin bath or resin impregnation system. Resin can also be injected directly into the die in some pultrusion systems.

The raw resin is almost always a thermosetting resin, and is sometimes combined with fillers, catalysts, and pigments. The fiber reinforcement becomes fully impregnated (wetted-out) with the resin such that all the fiber filaments are thoroughly saturated with the resin mixture.

As the resin rich fiber exits the resin impregnation system, the un-cured composite material is guided through a series of tooling. This custom tooling helps arrange and organize the fiber into the correct shape, while excess resin is squeezed out, also known as debulking. This tooling is known as a pre-former. Often continuous strand mat and surface veils are added in this step to increase structure and surface finish.

Once the resin impregnated fiber is organized and removed of excess resin, the composite will pass through a heated steel die. Precisely machined and often chromed, the die is heated to a constant temperature, and may have several zones of temperature through-out its length, which will cure the thermosetting resin. The profile that exits the die is now a cured pultruded Fiber Reinforced Polymer (FRP) composite.

This FRP profile is pinched and pulled by a gripper system. Either caterpillar tracks or hydraulic clamps are used to pull the composite through the pultrusion die on a continuous basis. At the end of this pultrusion machine is a cut-off saw. The pultruded profiles are cut to the specific length and stacked for delivery. Pultrusion is the only continuous manufacturing process for obtaining high quality composite profile, with high mechanical properties. Pultruded products are compose of high performance fibres (glass, carbon, aramid) embedded in a polymer matrix.


The process is characterized by:

  • Wide choice of reinforcement and resins
  • Low scrap rates
  • Complex shape and unlimited length
  • Low labour content
  • High raw material conversion efficiency
  • Consistent quality
  • Attractive cost

Reinforcement types

  • When choosing reinforcements, three characteristics must be considered:
  • The fiber type (glass fibre, aramid and carbon)
  • The form (roving strands, mat & fabrics)
  • The orientation

Resins types

  • Unsaturated Polyester resins
  • Epoxy Resins
  • Vinyl Ester Resins
  • Other resins