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Common problems and cause analysis of gelcoat in application

Sep 02, 2019


(1) mold surface electrostatic, mold agent did not dry, mold agent selection improper.

The rubber coat is too thin, the temperature is too low.

Gelcoat by water, oil or oil contamination.

(4) mold dirty or wax aggregation.

(5) low viscosity and thixotropic index.


(1) gelcoat thixotropic index is low, gel time is too long.

(2) gelcoat spraying too much, the surface is too thick, nozzle direction is not right or small diameter, pressure is too large.

(3) mold surface coating release agent is wrong.

The product gelcoat has bad luster

(1) mold smoothness, surface dust, etc.

(2) less curing agent content, incomplete curing, low curing degree, not after curing.

(3) the environment temperature is low, high humidity.

(4) gelatine layer is not completely cured on the mold.

(5) inside the rubber coat filling material is high, less matrix resin content.

Product surface fold

Common diseases for gelcoat. The reason is that the gelcoat is not fully cured that is premature coating resin, styrene to dissolve part of the gelcoat, swelling and wrinkle.

There are the following ways to deal with:

(1) check the thickness of gelcoat is in accordance with the specified value (0.3-0.5mm, 400-500g/㎡), when necessary, can be appropriate thickness.

(2) check resin properties.

(3) check the amount of initiator and mixing effect.

(4) check whether the addition of pigments affect resin curing.

5. Increase the workshop temperature to 18-20℃.

Pinhole on the surface of

When small bubbles lurk in the gelatine coat, pinholes appear on the surface after curing. Mold surface dust can also cause pinholes. The solutions are as follows:

(1) clean the mold surface, remove dust.

(2) check the viscosity of resin, when necessary with styrene and dilute, or reduce thixotropic agent dosage.

(3) such as release agent selection improper, will cause poor and pinhole, need to check the release agent. This does not happen with polyvinyl alcohol.

(4) add initiator and pigment paste, do not mix with air.

5. Check the spray speed. If the jet speed is too high, it will produce pinholes.

6 check atomization pressure, do not make too high.

7 check resin formulation. Excessive initiator can result in pregels and latent bubbles.

We check whether the grade and model of methyl ethyl ketone peroxide or cyclohexanone peroxide is appropriate.

Surface roughness variation

The surface roughness changes as spots, uneven gloss. May result from premature movement of the product on the mold or insufficient wax release agent.

The solutions are as follows:

(1) do not wax too much, but the amount of wax should be able to achieve surface polishing.

(2) check whether the mold release agent has been fully cured.