Gelcoat orgel coat is a material used to provide a high-quality finish on the visible surface of afibre-reinforced composite. The most common gelcoats arethermosetting polymers based onepoxy or unsaturatedpolyester resin chemistry. Gelcoats are modified resins which are applied tomoulds in the liquid state. They are cured to form crosslinkedpolymers and are subsequently backed withthermoset polymer matrix composites which are often mixtures of polyester resin andfiberglass, or epoxy resin which is most commonly used with carbon fibre for higher specific strength.
The manufactured component, when sufficientlycured and removed from the mould, presents the gelcoated surface. This is usuallypigmented to provide a coloured, glossy surface which improves the aesthetic appearance of the article, such as the surface of a boat hull.
Many marine craft and some aircraft are manufactured using composite materials with an outer layer of gelcoat, typically 0.5 mm to 0.8 mm (0.02 in to 0.03 in) thick. Gelcoats are designed to be durable, providing resistance toultraviolet degradation andhydrolysis.
Specialized gelcoats can be used to manufacture the moulds which in turn are used to manufacture components. These require very high levels of durability to overcome the mechanical and thermalstresses encountered during the curing and demoulding processes. Most fiberglass molds have non-conductive tooling gelcoats that accumulate static electricity, resulting in safety risks and difficulties in handling. Advancements in conductive tooling gelcoates with single wall carbon nanotubes (SWCNTs) make molds safer and easier to use by reducing dust attraction, combating electric shocks to workers, and eliminating issues with de-molding.[1]
Suitable resin chemistries for the manufacture of gelcoats vary, but the most commonly encountered areunsaturated polyesters or epoxies. Within each of these categories, the resin chemistries are further subdivided.
In addition to any pigment, if necessary a gelcoat will contain athixotropic additive to assist its tenacity to vertical portions of the mould whilst it cures.