What is a Gel coat finish?
Gel coat is a pigmented polyester resin used in open molding, bag molding, resin transfer molding, etc. (But not the pultrusion process) for these reasons.
1) It serves as a release agent: Without gel coat the resin would eat through the waxed surface of the mold and the fiberglass parts would stick in it. Gel coat has a gel time of approx. 10 minutes (not enough time to attack the wax); while polyester resin takes approximately 20 minutes to gel and can penetrate the wax.
2) Pigments in the gel coat as well as added UV stabilizers protect the resin from the harsh rays of the sun. Without gel coat the resin would oxidize away in a very short time leaving nothing covering the fiberglass sheet.
3) Color is added to the Gel coat.
Kept under cover or out of direct sunlight, it will last for years. But it oxidizes quickly in direct sunlight (Not a good finish for exterior applications). A 15 mil thickness is optimal. Excessive gel coat thickness can cause cracking and crazing due to flexing and twisting (doors and frames get twisted a lot during installation). If it is applied under 8 mills the gel coat will lift and wrinkle like the hide on an alligators back (A problem known as alligation). This is the reason for specifying 15 mills. They have to have that thickness.
When the Gel coat gets damaged it is very hard to repair it. Gel coat is very difficult to post apply. The material has a very heavy viscosity making it hard to apply smoothly. It must be catalyzed giving it short working times and a wax solution must be added to allow curing in the presence of air and moisture. Gel coat repairs always show there is no way to get an exact match of old and new colors.
Why we use paint with a polyurethane coating.
Universal Pultrusions L.L.C. offers an applied polyurethane coating (the highest quality industrial finish available). It is used throughout the world on everything from oil rigs to amusement parks. It is stronger than polyester gel coat. It is more resistant to the relentless effects of UV radiation and air-borne corrosives. Finishes are a two-part aliphatic polyurethane low VOC, industrial coating with a thickness of 5 mils. All finish products have gloss sheen with an impact resistance of 140 in-lbs and an electrical resistance: less than 10 megohms.
Polyurethane finishes are not susceptible to chalking, discoloring and leaching. The polyurethane finish also maintains a high gloss finish that lasts for years.
Our products come in primed for field painting or prefinished in one of our 10 standard colors and most custom colors can be matched.
Because of the type of finish we use on site damage can be repaired using standard products.