The polyester resin can be further chemically defined by the characteries. These categories are described as Orthophthalic (Ortho), Isophthalic (Iso). Vinyl has a unique chemical composition and has many working properties with polyester.

Ortho resins are based on orthogonal acids and are a good basic, versatile, and inexpensive resin.

They have a styrene content of between 35% and 45% for applications that do not require high operating temperatures, high corrosion resistance or high mechanical properties.

ISO resin is one step higher than the ortho resin and is more suitable for corrosive environments, high service temperatures and greater mechanical properties. Iso resins have 42% to 50% styrene because higher molecular weights require more solvent to produce a viable viscosity. Compared to orthogonal resins, Iso’s better performance does bring higher costs.

vinyl resins are used in applications requiring high surface finish. This is due to its low volume shrinkage. Physical properties are similar to ortho resins, but toughness is sacrificed with the ability to produce strong secondary bonds. It has a low styrene content ranging from 35% to 38%. Vinyl resins are often blended with other resins to minimize the negative aspects of these resins and add positive aspects.

Vinyl is used in applications with superior corrosion resistance or toughness properties. Vinyesters is a formulation of epoxy and methacrylic acid that produces polymers with polyester and epoxy properties. .