Fisheye
① There is static electricity on the surface of the mold, the release agent is not dry, and the selection of release agent is improper.
② The gel coat is too thin and the temperature is too low.
③ Gel coat contaminated with water, oil, or oil stains.
④ Dirty or waxy aggregates in the mold.
⑤ Low viscosity and thixotropic index.
Sagging
① The thixotropic index of gel coat is low, and the gel time is too long.
② Excessive spraying of gel coat, surface too thick, nozzle direction incorrect or small diameter, excessive pressure.
③ The release agent applied on the surface of the mold is incorrect.
The gloss of the product gel coat is not good
① The smoothness of the mold is poor, and there is dust on the surface.
② Low content of curing agent, incomplete curing, low curing degree, and no post curing.
③ Low ambient temperature and high humidity.
④ The adhesive layer is demolded before fully curing.
⑤ The filling material inside the gel coat is high, and the matrix resin content is low.
Surface wrinkles of the product
It is a common disease of rubber coating. The reason is that the gel coat is not fully cured and is coated with resin too early. Styrene dissolves some of the gel coat, causing swelling and wrinkling.
There are the following solutions:
① Check if the thickness of the gel coat meets the specified value (0.3-0.5mm, 400-500g/㎡), and if necessary, thicken it appropriately.
② Check the resin performance.
③ Check the amount of initiator added and the mixing effect.
④ Check if the addition of pigments affects resin curing.
⑤ Raise the workshop temperature to 18-20 ℃.
Surface pinholes
When small bubbles lurk in the gel coat, pinholes appear on the surface after solidification. Dust on the surface of the mold can also cause pinholes. The handling method is as follows:
① Clean the surface of the mold to remove dust.
② Check the viscosity of the resin, dilute it with styrene if necessary, or reduce the amount of thixotropic agent used.
③ If the release agent is not selected properly, it can cause poor wetting and pinholes. It is necessary to check the release agent. This phenomenon will not occur with polyvinyl alcohol.
④ When adding initiators and pigment paste, do not mix with air.
⑤ Check the spraying speed of the spray gun. If the spraying speed is too high, pinholes will be generated.
⑥ Check the atomization pressure and do not use it too high.
⑦ Check the resin formula. Excessive initiator will cause pre gel and latent bubbles.
⑧ Check if the grade and model of methyl ethyl ketone peroxide or cyclohexanone peroxide are appropriate.
Surface roughness variation
The changes in surface roughness are manifested as speckled spots and uneven glossiness. Possible sources include premature movement of the product on the mold or insufficient wax release agent.
The overcoming methods are as follows:
① Do not apply too much wax, but the amount of wax should be enough to achieve surface polishing.
② Check if the product release agent has fully cured.
Gel coat shattered
The breakage of the gel coat may be caused by poor bonding between the gel coat and the base resin, or sticking to the mold during demolding, and specific reasons should be identified to overcome.
① The surface of the mold is not polished enough, and the adhesive coating is sticking to the mold.
② The wax has poor quality and performance, thus penetrating the gel coat and damaging the wax polishing layer.
③ Surface contamination of the gel coat affects the adhesion between the gel coat and the base resin.
④ The curing time of the gel coat is too long, which reduces the adhesion with the base resin.
⑤ The composite material structure is not compact.
Internal white spots
The white spots inside the product are caused by insufficient resin penetration of the glass fiber.
① During the laying operation, the laminated products are not fixed enough.
② First lay dry felt and dry cloth, then pour resin to prevent impregnation.
③ Laying two layers of felt at once, especially the overlapping of two layers of cloth, can cause poor resin penetration.
④ The resin viscosity is too high to penetrate the felt. A small amount of styrene can be added, or low viscosity resin can be used instead.
⑤ The resin gel time is too short to be compacted before gel. The dosage of accelerator can be reduced, initiator or polymerization inhibitor can be changed to extend the gel time.
Layered
Delamination occurs between two layers of composite materials, especially between two layers of coarse grid cloth, which is prone to delamination. The reasons and overcoming methods are as follows:
① Insufficient resin dosage. To increase the amount of resin and impregnate evenly.
② The glass fiber is not fully saturated. The resin viscosity can be appropriately reduced.
③ Surface contamination of inner glass fiber (or cloth/felt). Especially when using the first layer to solidify before laying the second layer, it is easy to cause stains on the surface of the first layer.
④ The first layer of resin coating is excessively cured. It can reduce the curing time. If it has been excessively cured, it can be ground rough before laying a second layer.
⑤ There must be a short cut fiber felt between the two layers of coarse grid cloth, and do not allow the two layers of coarse grid cloth to be laid continuously.
Small spot
The surface layer of the gel coat is covered with small spots. It may be caused by poor dispersion of pigments, fillers, or thixotropic additives, or by gray surface area on the mold.
① Clean and polish the surface of the mold, then apply a rubber coat.
② Check the mixing efficiency.
③ Use a three roll grinder and a high-speed shear mixer to disperse the pigment well.
Color change
Uneven color density or appearance of color stripes.
① The pigment has poor dispersion and floats. It should be thoroughly mixed or the pigment paste should be changed.
② Excessive atomization pressure during spraying. Adjustments should be made appropriately.
③ The spray gun is too close to the surface of the mold.
④ The adhesive layer is too thick in the vertical plane, causing glue flow, sinking, and uneven thickness. The amount of thixotropic agent should be increased.
⑤ The thickness of the gel coat is uneven. The operation should be improved to ensure even coverage.
Fiber morphology exposed
The form of glass cloth or felt is exposed on the outside of the product.
① The gel coat is too thin. The thickness of the gel coat should be increased, or surface felt should be used as the bonding layer.
② Gel coat is not gel, and resin and glass fiber base are coated too early.
③ The product demolding is too early, and the resin has not yet fully cured.
④ The resin exothermic peak temperature is too high.
The dosage of initiators and accelerators should be reduced; Or change the initiator system; Or change the operation to reduce the thickness of the coating layer each time.
Surface small orifice
The surface of the mold is not covered with a gel coat, or the gel coat is not wet on the surface of the mold. If polyvinyl alcohol is used as a release agent, this phenomenon is generally rare. The release agent should be checked and replaced with paraffin wax without silane or polyvinyl alcohol.
Bubbles
Surface presents bubbles, or the entire surface has bubbles. During post curing after demolding, bubbles can be found in a short period of time or appear in a few months.
Possible reasons may be due to air or solvents lurking between the gel coat and substrate, or improper selection of resin systems or fiber materials.
① When covered, the felt or cloth is not soaked with resin. It should be better rolled and soaked.
② Water or cleaning agents have contaminated the adhesive layer. Please note that the brushes and rollers used must be dry.
③ Improper selection of initiators and misuse of high-temperature initiators.
④ Excessive usage temperature, exposure to moisture or chemical erosion. A different resin system should be used instead.
Cracks or cracks
Immediately after solidification or a few months later, surface cracks and loss of gloss are found on the product.
① The gel coat is too thick. It should be controlled within 0.3-0.5mm.
② Improper resin selection or incorrect initiator pairing.
③ Excessive styrene in the gel coat.
④ Undercuring of resin.
⑤ Excessive filling in the resin.
⑥ Poor product configuration or mold design results in abnormal internal stress during product use.
Star shaped crack
The appearance of star shaped cracks in the gel coat is caused by the impact on the back of the laminated product. We should switch to using gel coats with better elasticity or reduce the thickness of the gel coat, generally less than 0.5mm.
Sinking marks
Dents are generated on the back of ribs or inserts due to resin curing shrinkage. The laminated material can be partially cured first, and then the ribs, inlays, etc. can be placed on top to continue forming.
White powder
During the normal service life of the product, there is a tendency for whitening.
① The gel coat is not fully cured. The curing process and the dosage of initiators and accelerators should be checked.
② Improper selection or excessive use of fillers or pigments.
③ The resin formula is not suitable for the required usage conditions.
Gel coat release mold
Before the substrate resin is coated, sometimes the gel coat has already come off the mold, especially at the corners. Often caused by the condensation of styrene volatiles at the bottom of the mold.
① Arrange the mold position to allow styrene vapor to escape, or use a suitable suction system to remove styrene vapor.
② Avoid excessive thickness of the gel coat.
③ Reduce the amount of initiator used.
Yellowing
It is a phenomenon where the gel coat turns yellow when exposed to sunlight.
① During the laying operation, the air humidity is too high or the material is not dry.
② Improper resin selection. Resin that is UV stable should be selected.
③ The benzoyl peroxide amine initiation system was used. Other triggering systems should be used instead.
④ Undercuring of laminated materials.
Surface sticky
Caused by surface undercooling.
① Avoid laying in cold and humid environments.
② Use air dried resin for the final coating.
③ If necessary, the dosage of initiators and accelerators can be increased.
④ Add paraffin to the surface resin.
Deformation or concurrent discoloration
Deformation or discoloration is often caused by excessive heat release during curing. The dosage of initiators and accelerators should be adjusted, or different initiator systems should be used instead.
The product deforms after being removed from the mold
① Premature demolding and insufficient solidification of the product.
② Insufficient reinforcement in product design should be improved.
③ Before demolding, coat with a rich resin layer or surface layer resin to achieve balance with the adhesive coating resin.
④ Improve the structural design of the product and compensate for possible deformation.
Insufficient hardness and poor rigidity of the product
It may be due to insufficient curing.
① Check if the dosage of initiators and accelerators is appropriate.
② Avoid laying in cold and humid conditions.
③ Store fiberglass felt or fiberglass cloth in a dry environment.
④ Check if the glass fiber content is sufficient.
⑤ Post cure the product.
Repair of product damage
The surface damage and depth of damage are only in the adhesive layer or the first reinforcement layer. The repair steps are as follows:
① Remove loose and protruding materials, clean and dry the damaged area, and remove grease.
② Scrub within a small area around the damaged area.
③ Cover the damaged area and ground areas with thixotropic resin, with a thickness greater than the original thickness, to facilitate shrinkage, grinding, and polishing.
④ Cover the surface with glass paper or film to prevent air obstruction.
⑤ After curing, remove the glass paper or peel off the film, and polish it with waterproof emery paper. First use 400 grit sandpaper, then use 600 grit sandpaper, and carefully grind to avoid damaging the gel coat. Then use fine friction compounds or metal polishing. Finally, wax and polish.
Post time: Feb-18-2024
