Gelcoat

A gelcoat is a hard lacquer that is applied as a protective layer to molded parts made of fiber-reinforced plastics (e.g. GFK , CFK, AFK ...). The gelcoat seals the component against moisture ( hydrolysis ) and protects against UV radiation and pressure damage.

composition

The gelcoat consists of synthetic resin thickened with silica , mostly unsaturated polyester UP or epoxy resin , but does not contain any glass fibers . The silica makes the surface more abrasion-resistant than the uncoated fiber composite molding.

It is often completely colored in order to make later paintwork damage less noticeable.

Application method

From the outside to the inside

The gelcoat is applied directly to the release varnish with which the negative form was treated. This can be done either with a brush or roller, or with a spray gun. After the gelcoat layer has hardened in the mold, the actual production of the molded part begins by inserting the glass fiber mats or fabrics in layers and then soaking them with synthetic resin.

From the inside to the outside

Gelcoat is often enriched with cobalt for the surface finishing of racing yachts in order to achieve better sanding properties, which lead to a smoother surface, and thus to a higher speed. For this purpose, gelcoat is applied in several layers to the prepared GRP hull . The processing takes place from the inside (body) to the outside (gelcoat). If a high-quality lacquer surface is desired, however, sandable, transparent gelcoats are used for the final layers of gelcoat , which leads to surfaces that can be seen especially on America's Cup boats .

properties

The various building materials (the hull is made of GRP, the gelcoat is a synthetic resin ) combine to form an almost completely homogeneous material - in terms of strength - which is neatly sanded after the first layer of gelcoat . By applying additional layers, each 0.5 to 0.8 mm thick and no longer needing to be sanded, a protective layer between 1 and 3 mm thick is created which, in addition to the speed aspect , above all offers excellent protection against osmosis damage .

application

The use of gelcoat became common in yacht construction with the advent of GRP construction, which resulted in lighter and faster boats, which increasingly required fine-tuning, which led to better sliding properties and higher speeds. Gelcoat surface refinement is also increasingly used in aircraft and motor vehicles with GRP bodies.

Ecological aspects

As with GRP, recycling of the fully polymerized resin-hardener mixtures is not possible with the current state of the art . Polymerized waste is classified as household waste.