Gel Coat Application Tips


Gel coat makes the surface of fiberglass products more beautiful and plays a role of protection preventing resistance to chemical erosion, bruise and aging. Not only hand lay-up products but also pultruded products can be attached gel coat. It is the key to the final quality of the product while choosing the high quality of the gel coat and the correct application process. In order to get a famous and beautiful FRP product, it’s vital and necessary that mold to fully processed in advance, the correct operation of the gel coat and the training of the operating personnel.

Whether injection or hand brush, when using the gel coat, you should pay attention to the points of the following application process.

1. Choose the suitable type of gel coat before using it.

2. Prepare the mold and thoroughly handle the surface of the mold before using it.

3. Stir the gel coat with constant speed in the cask to mix intensively preventing air.

4. If you want to get a beautiful surface after solidify, you should know the recommend work temperature of gel coat and mold is 15℃ to 30℃, and the ideal temperature is that mold higher than gel coat 2℃ to 3℃ before using it.

5. The workshop RH is lower than 80%. You should increase the curing temperature if the humidity is high. Also, you should prevent water from gathering on the surface of the mold.

6. The new mold should be preprocessing and the surface need polished carefully and waxed fully. Don’t use the mold rel containing silicone oil. Spraying gel coat after the water evaporation, when you use the water soluble mold rel.

7. Don’t add solvent dilution, such as lacquer thinner, acetone and so on, when you use gel coat. You can mix little cinnamene(≤2%), if you want to decrease the viscosity when used.

8. The curing agent of the gel coat is methyl ethyl ketone peroxide and the dosage is around 1% to 2%. The degree of cure will be influenced, decrease the water resistance and weatherability, while the dosage of curing agent is more or less.

9. Please make sure the pigment is stable and uniform if you add the pigment by yourself. And pay attention to the dosage, according to the recommended dosage and weight accurately, using low shear mixing equipment.

10. You should paint 2-3 times, in order to get a suitable thickness, meanwhile get a better deaeration effect.

11. You should choose the suitable nozzle, jet pressure, bulk range and elevation direction. The spray gun should be a uniform translation, then move the nozzle to the out of the mold, and stop. Make sure the air is clean and dry when you jet the gel coat.

12. You can get a smooth surface, while the jet thickness is 0.4-0.6mm(equivalent to 500-700g gel coat per square meter). Thickness can be determined by the thickness gauge. Too thick, easy flow, cracking and pinhole, in contrary, causing less curing.

13. For the part of the difficulty of the mold, such as a deep groove, the jet gun can’t keep a reasonable position, you must use the brush. You can allow a small amount of ventilation, due to the gelation time is longer than the other.

14. Ensure mold with good ventilation, because the styrene monomer plays an inhibitive role,  and will sink in the mold cavity, due to the molecular weight is bigger.

15. Once the gel coat fully cured(when you click the gel coat only stick without attachment in hand), take the next step of operation.

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