Iso & Ortho - Polyester Resins were once the standard products for hand layups.
Many manufacturers are shifting towards Vinyl-Ester and Epoxy Resins
, due to their better laminate qualities:
~ Better Blister-Resistance
~ Better Hydrolytic Properties (Water Resistance)
~ Stronger Bonding Properties (Adhesive Strength)
~ Lower Styrene Emmissions (MACT Restrictions).
Or, so I'm told...
and from BoatUS “BoatTECH Guides” :
”Resin Boat Talk”
- From http://www.boatus.com/boattech/ResinBoatTalk.htm
Polyester, epoxy, and vinylester resins are the basis of barrier coats and fillers. The viscosity of all three allows for an easy, flowing application. Several types of thickening and strengthening products are availabl, such as reinforced short-strand glass fibers, which turn the products from a thin, syrupy consistency to a thick putty.
Polyester Resin - How It Works:
Combines with the catalyst Methyl Ethyl Ketone Peroxide (MEKP) to create a hardened product.
Repairing any polyester product, including most fiberglass
The least expensive of the three resins, polyester can be used over a broader range of temperatures than vinylester. It's not necessarily good for bonding to vinylester or epoxy. It's most siutable for above waterline repairs
because it tends to let water pass through more easily than epoxy or vinylester, so it's more prone to blistering.
Epoxy Resin - How It Works:
Cures basically in the same manner as two-part polyester resin, but uses different chemical bases that provide better adhesion, strength, hardness, durability and water resistance.
Wood, plastic, and fiberglass
repairs above or below the waterline and as a barrier coat.
Epoxy won't blister like polyester because it absorbs less water. If your original repair was made with an epoxy, then it's best to stay with an epoxy. Epoxy is more expensive and tends to take longer to cure than polyester and vinylester - generally 24 hours between coats. Meticulous surface preparation is required. You must sand the surface free of amine blushes (which come to the surfacesuring the curing process) before applying gelcoat
, primer, and paint
. Apply 4-6 hours after sanding
. Not recommended for use when you have a minimum amount of time.