What is polyester gel coat and how to use it

The polyester gel coat is the product that gives a new look to composite material parts. It provides colour, gloss, surface hardness, weather resistance, water resistance, scratch resistance…

Do you want your parts to have a new look? At Feroca we help you with our polyester gel coat product to give your new composition a special finish.

What is Polyester Gel Coat

Polyester gel coat, as mentioned above, is a material that provides a high-quality finish on the visible surface of a composite polymeric material. It is used as the first registration layer, which is then filled with polyester. It is manufactured from isophthalic unsaturated polyester resin. It also provides a perfect mould finish on fibre laminates.

It is the first layer of resin applied to the prepared mould, forming the finish of one of the laminate surfaces, providing protection against chemicals, weathering, moisture, or any environmental damage. In general, gel coats offer greater resistance to abrasion, corrosion, UV radiation, and temperature changes than their corresponding base resins.

The manufactured component, once cured and removed from the mould, presents the gel coat layer on its surface. This is generally pigmented to provide a glossy coloured surface, which improves the aesthetic appearance and gives your compositions a new lease of life.

Polyester Gel Coat Uses

Polyester gel coat is applied as the first layer, once the mould has been waxed. It allows you to obtain parts with a perfect finish, with all the mould detail and good resistance to weathering and water contact. It can be used in the following situations:

• In the automotive industry. More large-scale parts are finished in gel coat, both interior and exterior. For example, bus or car bumpers.

• Construction. Certain elements are painted with gel coat, which provides greater protection and a good finish (water tanks, septic tanks, transparent sheets…).

• Decoration and window display. Figures for interior decoration, display stands...

• Theme parks and architectural elements. Essential for adding visual appeal to attractions and achieving greater resistance in water parks.

• In repairs. It is a highly valued product when repairing fibreglass-reinforced polyester parts that have scratches, scrapes, or are worn.

Difference between Gel Coat and Topcoat

Gel coat and topcoat are formulated using a polyester resin, vinyl ester resin, or a modified resin, to which various additives, dispersants, levelling agents, deaerators, UV filters, and pigments are subsequently added, giving them their final properties.

There is practically no difference between these two products. A topcoat is simply a gel coat to which a percentage of a paraffin solution has been added, most often paraffined styrene (10% paraffin solution).

How to Apply Polyester Gel Coat

The application of gel coats is common to all types and qualities. In the manufacture of parts with higher added value or technical requirements, the application parameters must be much more carefully controlled. The influence of these parameters is directly related to the final quality of the gel coat layer.

Therefore, it is of the utmost importance to be very careful with the recommendations. You should follow the step-by-step instructions provided on the product label and if you have any questions, contact our experts.

Gel coat can be applied with a spray gun, roller, or brush. For best results, application with a spray gun is recommended, as it allows for more uniform and consistent layer thickness. In enclosed spaces or hard-to-reach areas, paint rollers can be used as an alternative.

Gel coat applied with a brush may show streaks and uneven thickness, which affects the quality of the finish. Very thick layers are brittle and may show surface cracking. Very thin layers are prone to wrinkling due to styrene attack from the laminating resin. Therefore, you must be very careful when applying gel coat with this method. If gel coat is applied by spraying, it can be done in a single coat.

Process for Creating a Polyester Gel Coat Part

1. Apply the Gel Coat to Your Mould

The gel coat must be applied to your part over a mould, whether rigid or flexible. The copy is taken from the mould. For the first registration layer, as mentioned above, we are going to use gel coat. You can add pigments of the colour you want to the mix so that it matches your part. In this case, you can use the pigments we offer at Feroca.

Then, simply spread it with a brush over the entire surface of the mould. You must pay special attention to all the nooks and crannies so that no bubbles are left behind.

2. Once Dry, We Do the Polyester casting

Once dry, we can do the polyester casting, following the step-by-step instructions on the product label.

3. We Mix the Polyester Resin with Marble Powder

For the filler, we are going to mix the polyester resin with marble powder in equal parts. This way we will achieve greater hardness. We mix it well so that no lumps or bubbles remain, and then we catalyse it with Feroca's catalyst for polyester resins.

4. Mix Well, Let It Cure and Done!

Once everything is well mixed, we do the casting and let it cure. When it has cured, we demould it and our polyester gel coat-reinforced part is ready.

The Best Polyester Gel Coat at Feroca

If you need to buy polyester gel coat, at Feroca we offer you the best product on the market that suits all types of manufacturing or repair projects.

If you have any questions, you can get in touch with us for more information and advice. We will be happy to help you!

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