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Common defects and prevention methods of hand laid FRP

The surface of the product is sticky

In the production process of FRP products, due to the product exposed to humid air, or the blower, electric fan and other exhaust equipment, the surface of the product is directly blown, resulting in excessive styrene volatilization, and finally there is no resin containing wax in the layer, which causes the surface of products to become sticky.

Treatment method:

1. Avoid making products at low temperature or humidity.

2. 0.02% paraffin was added into the resin to prevent the polymerization inhibition of oxygen in the air.

3. Control the direction of ventilation, avoid ventilation and reduce the volatilization of crosslinking agent.

4. According to the indoor environment temperature, the amount of initiator and accelerator should be controlled.

5. Or use paraffin resin directly.


The wrinkling of FRP products often occurs in the gel coat. Before the first coating of the gel coat is completely gel, second layers of gel coat are formed, which causes the styrene in the second layers of gel coat, which partially dissolves the first layer of gel coat, causing swelling and wrinkling.

Treatment method:

1. The temperature of the working environment should be properly raised. When the first layer of gel coat is applied, the second layer of gel coat should be applied after drying with infrared bulb,

2, after the gel layer is coated, then coat the resin. It is suitable to increase the amount of initiator and accelerant properly and control the ambient temperature of the working room between 18 ℃ and 20 ℃.

eye of a needle

The surface of the needle is mainly due to the small bubbles entering the gel coat before the gel, or the dust on the surface of the mold, or when the flame retardant resin is added, the viscosity is too high to add solvent evaporation, leaving a needle eye.

processing method

1. During the molding process, the impregnating roller should be used to drive away the bubbles

2. It is suitable to add defoamer into resin, such as silicone oil, etc

3. Control the working environment, the surrounding humidity should not be too high, high temperature should not be too low

4, the amount of catalyst should not be too much to avoid premature gelation and produce bubbles.

5. The added material should not be affected by moisture, if it is damped, it needs to be dried

6. Keep the mold surface clean.

Low Gloss

The surface glossiness of FRP products is not good, the common phenomenon is: local no spot piece, or all the surface lose luster.

The main reason is that the products are demoulded prematurely, or the mold release agent is not selected well, or the mold surface is not dry.

Treatment method:

1. Before using the mould, it is necessary to fully polish it. After waxing or polishing, clean gauze should be used on the surface of the mould to wipe off the redundant coating;

2. After the product is fully cured, demoulding can be started

3. Keep the mold surface dry

Gel coat peeling off

If the product solidifies too fast, the gel coat layer becomes brittle; when the product is demoulded, the strength on the back of the product is too strong, resulting in the gel coat layer peeling off; or the gel coat layer of the layer is not compacted; or there are impurities on the mold surface, which will cause the surface gel coat decoration to peel off.

1. Treatment method: properly reduce the amount of curing agent and accelerator, and master the curing degree of gel coat layer;

2. The surface contamination should be removed carefully;

3. When paving, the impregnating roller shall be used for rolling compaction.

Dry spots appear inside the product

The main reason for dry spots in FRP products is that the resin is not saturated.

Treatment method:

1. Reduce the viscosity of the resin and increase the amount of styrene appropriately;

2, reduce the dosage of accelerator, adjust the gel time of the resin, so that the ply can be fully compacted.


The main reasons for the delamination of the products, such as insufficient resin content and uncompacted layer, moisture in FRP fiber felt due to air humidity, or glass fiber cloth treated with non reinforced sizing agent;

Or the wax treated precursor is not treated with wax, or the second layer can be pasted after the first layer is completely solidified in the molding operation, which will lead to delamination of products.

Treatment method:

1. Glass fiber fabric should be treated with reinforced sizing agent as much as possible. If there is wax, dewaxing should be carried out. If there is moisture in glass fiber fabric, it must be dried

2. When pasting, it is necessary to control the amount of glue liquid, and brush with force to make the layer dense and eliminate bubbles

3. If the layered curing method is adopted, it is not suitable to wait until the first layer is completely cured before pasting the second layer.

Uneven color

The main reasons for the uneven color of products are: uneven dispersion of pigments and insufficient mixing; out of date pigments and insufficient layered ingredients; uneven coating resin and uneven thickness; or glue flowing phenomenon when brushing vertical surface; or excessive pressure of spray gun, too close to mold surface, etc.

Treatment method:

1. Pigment, such as carbon black, needs to be fully ground by a grinder and mixed with resin to make the pigment disperse evenly;

2. Thixotropic agent should be added into the resin to avoid gum flow on the vertical surface;

3. When brushing gel coat, it must be painted evenly to avoid uneven coating thickness on the same plane.

Spots, fish eyes and depressions

The spots on the surface of gel coat may be caused by uneven dispersion of pigment, filler or thixotropic agent, or dust on the surface of mould.

Treatment method:

1. Polish the surface of the mould and ensure that the surface of the mould is clean; pay attention to the effect of material mixing; use the roller grinder colloid mill to make the pigment disperse evenly.

2. Fish eye and depression often appear in the middle of gel coat layer, which may be caused by insufficient impregnation of gel coat resin on the mold surface. If the polyvinyl alcohol release agent is used, fish eye will rarely appear. However, fish eye defects often occur when silicone modified release agent is used.

Fiber exposure

The main reasons for fiber exposure are: the gel coat layer is too thin; or the gel coat layer is not fully cured before


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