Resin Comparison: A More In Depth Look at Resin Differences.

A majority of fiberglass parts are constructed of polyester resin.
Good general purpose resin.
Excellent for most repairs.
Provides a repair that has similar strength & flexural characteristics to the original part.
Tolerant of temperature and catalyst variations during lay-up.
Wets out fabrics quickly and easily.
Isothalic polyester resin is more water & heat resistant than orthothalic polyester resin.

Exhibits higher strength characteristics than orthothalic resin.
About 90% repairs on a fiberglass boat can be made with this resin.
May be used for molds because of its better abrasion resistance and heat tolerance.
Has better UV and water resistance.
More corrosion resistant than orthothalic polyester resins.
Has greater impact resistance due to its increased strength and flexibility.
May be used for underwater repairs.

Stronger and more durable than polyester resin.
Most professional repairs are done in vinylester.
Makes strong stiff laminates.
Excellent bond strength to sanded laminate and core materials.
Will bond to epoxy resin.
Higher resistance to chemical, water and UV than polyester resin.
Higher resistance to vibration and shock loads.
Due to its higher strengths it has better tensile and flexural characteristics
Highly resistant to water absorption that causes osmotic blistering that can occur with polyester resins.

Has higher ultimate strength than polyester or vinylester resins.
Adheres well to wood, aluminum & steel.Excellent for covering wood with fiberglass.
Can be thickened with additives to make a wood glue or a structural putty to replace rotted wood.
Has electrical insulation properties.
Has the strongest bond with carbon and kevlar reinforcements.
Has better flexibility than polyester or vinylester.
Can withstand substantial impact without cracking.
Higher resistance to to environmental and thermal degradation than polyester.
Has lower shrinkage than polyester or vinylester resins.
Epoxy laminate generally requires much less labor to fair.

All three resins have their own unique roles to play in fabrication and repairs.

How do they compare in cost?

Epoxy is the most expensive, Polyester is least expensive & Vinylester is in the middle of the two.

What materials work with these resins?

Over 95% of all boats, truck & car bodies are made of E-Glass(orthothalic polyester resin and isothalic gelcoat)

Polyester or vinylester are much better to use than epoxy for polyester fiberglass repairs.
Generally on the scale of strength, water resistance and bond strength, Epoxy and Vinylester are the best, Isothalic Polyester is in the middle and Orthothalic Polyester is the weakest.
Vinylester may also be used over polyester resin to help prevent osmotic blistering.