Unsaturated Polyester Resin and Gelcoats

Unsaturated polyester resins are the simplest, most economical resin systems that are easiest to prepare and show good performance.  Generally, polyesters exhibit somewhat limited thermal stability, chemical resistance, and process ability characteristics. 

Applications include transportation markets (large body parts for automobiles, trucks, trailers, buses), marine (small and large boat hulls and other marine equipment), building (panels, bathtub and shower shells), appliances etc.

Orthophthalate Resins

Orthophthalic Is also referred to as ortho or General Purpose Polyester (GP) was the original polyester developed. It has the lowest cost and is still very widely used in FRP industry. It is commonly used in applications where high mechanical properties, corrosion resistance, and thermal stability are not required. Although the upper-temperature limit is only 50oC, it performs satisfactorily in water and seawater. It is normally not recommended for use in contact with chemicals.

The main Applications are hand lay up, RTM, putties, roofing sheets, etc.

Types Available: 

  • General purpose resin
  • General purpose resin economy
  • General purpose  LV
  • General purpose UV
  • General purpose FR resin
  • General purpose boat grade resin
  • General food grade resin

Isophthalate Resins

Often referred to as ISO, it is improved polyester. It has a slightly higher cost, improved strength, thermal stability(55oC) and mild resistance to corrosion conditions. Improved resistance to water permeation has prompted its use as a gel barrier coat in marine applications. Improved chemical resistance has led them to extensive use in underground petroleum tanks (in gas stations) with satisfactory service life. 

They are also used in salts and mild acids and in automobile and marine applications, corrosion resistant tanks, etc.

Types Available: 

  • ISO Chemical Resin
  • ISO NPG Resin
  • ISO Boat Grade Resin
  • ISO Fire Retardant Resin
  • ISO Mechanical Resin

Superior Grade Resins

Even further improved polyester, it is bisphenol chlorinated, or a combination of polyester and epoxy. Its curing, handling and processing characteristics are those of polyester, and it exhibits higher test results in corrosion temperature resistance and strength and has higher cost. Modifications of the molecule have produced even higher properties.

Types Available: 

  • Vinylester Resin
  • Bishphenol Resin
  • Super Vinylester Resin


Gel coats are prepared from a base resin and additives. The base resin can be polyester, vinyl ester, phenolic or epoxy. Additives are thixotropic agents, fillers, pigments and other. The gel coat, as the name implies, has a gel texture. This makes the gel coat capable to “stay” on vertical surfaces of moulds without draping. It is placed first in the mold, so it becomes the outer surface of the construction. It is used to replace paint, for cosmetic purposes, and to protect from the environment.

Gelcoats have a good gloss, resistance to cracking during re-molding and have low porosity finish

Gelcoats are used in automobile and marine applications, sanitary wares, etc.

We have a respective gelcoat to be used with every type of Resin we offer:

Types Available: 


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