You may know that resins are commonly used in pultrusion, but why are they so vital?
According to AZO Materials:
The introduction of ultraviolet (UV), thermal energy, or radio frequency (RF) waves makes individual polymer chains within the resin to undergo cross-linking reactions that create a polymer network that is both insoluble and infusible.
Cross-linking is defined as the creation of covalent bonds between separate polymer chains in a thermoset resin. This is related to various factors, including the distribution and nature of monomers throughout the resin and the particular crosslinking mechanism.
Luckily, the range of epoxies, acrylics, phenolics, and different thermoset resins employed in pultrusion have been outlined in enough detail to ensure the homogeneity of the polymer network in a cured composite part.
In this article, Strongwell will describe how and why thermoset resins are utilized in pultrusion in greater detail.
How are Thermoset Resins Used?
Fiber reinforced composite (FRP) materials are produced by impregnating glass-reinforced textiles with a high-performance thermoset resin and curing the combination of materials after a formation stage.
In a standard pultrusion method, mat creels secure the textile where it can be fed into the reinforcement guide. The textile is then drawn through a resin bath where it is put under a ‘wet-out’ procedure.
This bath holds the thermoset resin with any further pigments, catalysts, or fillers required to boost cross-linking throughout the curing phase. The textile becomes entirely saturated by this resin mixture before passing through a constrictive pre-former.
This is critical for optimal positioning and organization of the reinforcements in the near-net-shape while taking away any further liquid from the impregnator before passing through the curing die.
Cross-linking occurs when the thermoset resin is heat-activated, commonly by electrical induction, or by a radio frequency (RF) wave generator. The energy generated by these instruments results in the curing of the thermoset resin with the reinforcing elements embedded within. It is then cooled before being cut to the correct length.
Why are Thermoset Resins Used?
Thermoset resins are mostly used to provide thermal and structural stability to the composite part. However, standard resin systems can be easily adjusted to reach the desired characteristics.
Even though pultruded polymer composites are impenetrable to melting, they may still be vulnerable to combustion or deformation at greater temperatures.
Different phenolics are employed to enhance the temperature resistance of polymer composites and increase their fire performance for difficult applications. Various thermoset resins are prescribed according to the area of application and customer specifications of customized parts.