Isocyanurates

Properties and Applications

Isocyanurates and their derivatives are specialty resins that are mainly used as coreactants for other resins in elastomers and plastics products. They are high quality trifunctional liquid or solid resins that increase the crosslink density which, in turn, greatly improves heat and chemical resistance as well as flame retardancy.

The isocyanurate structure is obtained by trimerization of an (aliphatic) isocyanate such HDI yielding a (trifunctional) isocyanurate. The trifunctional resins can be functionalized with various hydroxyl monomers in a subsequent step. Functional isocyanurates can also be directly prepared by trimerization of monoisocyantes having another functionality. Three important isocyanurate derivatives are triglycidyl isocyanurate (TGIC), triallyl isocyanurate (TAIC), and tris(2-hydroxethyl) isocyanurate (THEIC) which are depicted in the Figure below.

Triglycidyl isocyanurate is a solid trifunctional epoxy resin. It is widely used as a cross-linker for high-solid powder coatings to improve the photochemical and thermal stability of the (appliance) coating. Other important applications include printed circuit boards, electrical insulations, and heat and chemical resistant thermosets. However, over the years, TGIC has been replaced with other resins in many products due to health and toxicity concerns.

Triallyl isocyanurate (TAIC) is a slightly yellowish liquid or white solid vinyl resin. It is mainly used as a crosslink agent and flame retardant in vinyl cured rubber and plastic products. The triazine ring structure and high functionality greatly improves heat and weather resistance, flame retardancy, and mechanical performance. Other applications include fluorine elastomers, EVA films for solar battery encapsulation, and various polymer alloys.

Tris(2-Hydroxethyl) isocyanurate (THEIC) is a hydroxy-functional resin that can be used as a coreactant in urethane, polyester, and epoxy thermosets and coating formulations to boost performance. This resin finds some applications in insulating vanishes for electrical wires, oil and water-soluble paints, and in laminates.

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