What type of resin is gel coat?

Gel coat is primarily made from polyester resin, which provides a smooth, durable finish and serves as a protective outer layer on composite structures, particularly in marine applications. The reason this is a common choice is that polyester resins are relatively low-cost, have good mechanical properties, and are easy to work with.

Epon, typically referring to epoxy resins, is more suited for applications requiring superior chemical resistance and adhesion but is not used for making gel coats since gel coats need to be less viscous and more affordable for use in mass applications like boat hulls.

Isophthalic resin is often used in other composite applications where increased chemical resistance and mechanical performance are required, but it is not the standard for gel coats, which are predominantly polyester-based. Vinyl ester resin is another option for high-performance composites but does not serve as gel coat primarily; it is used for applications needing enhanced strength and corrosion resistance.

Thus, the most accurate answer reflects the typical formulation found in gel coats, which is standard polyester resin, widely recognized for its properties suited for exterior finishes on boats and other composite applications.