Thermoset Plastic Resins for Molding/Machining

Traditional Fiber Reinforced Polymer Composites, or FRP Composites for short, use a thermosetting resin as the matrix, which holds the structural fiber firmly in place. Common thermosetting resin include:

  • Polyester Resin
  • Vinyl Ester Resin
  • Epoxy
  • Phenolic
  • Urethane

The most common thermosetting resin used today is polyester resin, followed by vinyl ester and epoxy. Thermosetting resins are popular because uncured, at room temperature, they are in a liquid state. This allows for convenient impregnation of reinforcing fibers such as fiberglass, carbon fiber, or Kevlar.

Properties and Benefits of Thermoset Resins

As mentioned, a room temperature liquid resin is easy to work with. Laminators can easily remove all air during manufacturing, and it also allows the ability to rapidly manufacture products using a vacuum or positive pressure pump. (Closed Molds Manufacturing) Beyond ease of manufacturing, thermosetting resins can exhibit excellent properties at a low raw material cost.

  • Properties of thermoset resins include:
  • Excellent resistance to solvents and corrosives
  • Resistance to heat and high temperature
  • Fatigue strength
  • Tailored elasticity
  • Excellent adhesion
  • Excellent finishing (polishing, painting, etc.)

In a thermoset resin, the raw uncured resin molecules are crossed linked through a catalytic chemical reaction. Through this chemical reaction, most often exothermic, the resin creates extremely strong bonds to one another, and the resin changes state from a liquid to a solid. A thermosetting resin, once catalyzed, it cannot be reversed or reformed. Meaning, once a thermoset composite is formed, it cannot be remolded or reshaped. Because of this, the recycling of thermoset composites is extremely difficult. The thermoset resin itself is not recyclable, however, there are a few new companies who have successfully removed the resin through pyrolization and are able to reclaim the reinforcing fiber.