Thermosetting Resin

Last updated: November 6, 2019

What Does Thermosetting Resin Mean?

A thermosetting resin is a petrochemical material that irreversibly cures. The cure may be brought on by heat, generally above 392°F (200°C), chemical reaction or suitable irradiation. It is used as adhesives as well as in semiconductors and integrated circuits.

The International Union of Pure and Applied Chemistry (IUPAC) defines a thermosetting resin as a petrochemical in an indulgent solid or viscous state that changes irreversibly into an infusible, insoluble polymer network by curing.

Thermosetting resins are popular because uncured and at room temperature they are in a liquid state. This allows for convenient impregnation of reinforcing fibers such as fiberglass/carbon fiber or Kevlar.

A thermosetting resin is also known as a thermoset.


Corrosionpedia Explains Thermosetting Resin

Thermosetting resins are rigid polymeric materials that are resistant to higher temperatures than ordinary thermoplastics. These materials are normally made up of lines of polymers, which are highly cross-linked.

The heavily cross-linked structure produced by chemical bonds in thermoset materials is directly responsible for the high mechanical and physical strength compared with thermoplastics or elastomers. However, it provides poor elasticity or elongation of the material—once hardened, a thermoset resin cannot be reheated and melted to be shaped differently.

The cross-linking process eliminates the risk of the product remelting when heat is applied, making thermosets ideal for high-heat applications such as electronics and appliances. Since their shape is permanent, they tend not to be recyclable as a source for newly made plastic.

Common thermosetting resins include:

  • Polyester resin
  • Vinyl ester resin
  • Epoxy
  • Phenolic
  • Urethane

Thermoset resins provide superior:

  • Resistance to solvents and corrosives
  • Resistance to heat and high temperature
  • Fatigue strength
  • Adhesion
  • Finishing (polishing, painting, etc.)

It is commonly used in:

  • Polyester fiberglass systems
    • Sheet molding compounds
    • Bulk molding compounds
  • Polyurethanes
    • Insulating foams
    • Mattresses
    • Adhesives
    • Synthetic fibers
  • Vulcanized rubber
  • Bakelite
  • Melamine
  • Epoxy resin used as glass-reinforced plastic
  • Polyimides used in printed circuit boards
  • Mold or mold runners



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