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A Comparative Analysis of ORTHO, ISO, and Vinyl Ester Resins in FRP Applications

Fiberr Labs

Dec 9, 2023

A comparison with the pros and cons of common FRP resin types

When comparing Orthophthalic (Ortho), Isophthalic (Iso), and Vinyl Ester (VE) resins for use in Fiberglass Reinforced Plastics (FRP), there are several key differences to consider:

Orthophthalic Resin: Known as a basic type of resin in the industry, orthophthalic resin is typically the least expensive option. However, it offers inferior properties in terms of strength, chemical resistance, and corrosion resistance when compared to isophthalic and vinyl ester resins. It is not recommended for use in contact with chemicals.

Isophthalic Resin: This resin is slightly more expensive than orthophthalic resin, but it offers better resistance to corrosion and chemicals. Isophthalic resins provide higher strength, better flexibility, and improved chemical resistance compared to orthophthalic resins. In laboratory tests, fiberglass reinforced isophthalic polyester resin panels showed notably higher flexural and tensile properties than panels using orthophthalic polyester resin.

Vinyl Ester Resin: This type of resin is more expensive than isophthalic resin but offers even higher strength and superior chemical and corrosion resistance. Vinyl ester is typically recommended for chemical processing areas and for structures that require additional strength.

In terms of application, isophthalic resin is often recommended for most grating applications due to its balance of strength, long service life, flammability, corrosion, and chemical resistance. Vinyl ester is generally recommended for structural profiles, ladders, handrail systems, and other structural products where the best performance and strength are needed.


Orthophthalic Resin

Isophthalic Resin

Vinyl Ester Resin


Least expensive

Slightly more expensive than Ortho

Slightly higher than Iso


Inferior compared to Iso and VE

Higher than Ortho

Higher than Iso

Chemical Resistance

Not recommended for chemical contact

Better than Ortho

Superior to both Ortho and Iso

Corrosion Resistance

Inferior compared to Iso and VE

Better than Ortho

Superior to both Ortho and Iso


Lower compared to Iso and VE

Better than Ortho


Recommended Applications

Basic FRP applications

Grating applications, general FRP use

Chemical processing areas, structural applications

These differences make each type of resin suited for specific applications within the FRP industry. The choice of resin will depend on factors such as the required strength, chemical resistance, and the specific environment in which the FRP product will be used.

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