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

ORTHOTHALIC POLYESTER RESIN:  LBI-301

• 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.

ISOTHALIC POLYESTER RESIN:  LBI-302

• 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.

VINYLESTER RESIN:  LBI-901 & LBI-902

• 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.

EPOXY RESIN:  LBI-1101

• 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?
  • Epoxy adheres to carbon fiber and kevlar better than vinylester or polyester.
  • Epoxy is also the best choice for laminating over wood.
• 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.