Defects, causes and prevention methods of gelcoat surface
1. pinhole
cause:
When spraying, air is mixed in, the solvent vapor is trapped in it, the amount of hardener is too large, the atomization is poor when spraying, the gun is too close to the mold surface and the gelcoat film thickness is uneven.
The solution:
Reduce spray pressure (2-5kg/cm2), slow curing, make spray thickness uniform but not thick, fine and even without air bubbles, control curing dose within 3%, properly reduce viscosity, increase spray width, and check distance while spraying. Within 40-70cm, the spray thickness is 0.3-0.5mm.
2. narrowing
cause:
The gelcoat is too thick (buildup, excessive amount of gelcoat).
The solution:
Formulate the right plan of material and spray evenly.
3. Row spacing (non-adhesive)
cause:
Insufficient wiping wax, silicone-based release agents tend to have obvious spacing, and water or oil is mixed when spraying.
The solution:
After fully wiping the wax, wipe it immediately until it is bright, use the wax or mold release agent correctly for the products and raw materials, use dry air, and install an oil-water separator.
4. Mixed foreign body
cause:
Small clots and foreign bodies in the gel coat, dirt on the surface of the mold, flying insects in the spray and dust in the production workshop.
The solution:
When using the filtered gel coat, the mold should be cleaned and cleaned before spraying the gel coat, and the static electricity on the surface of the mold should be eliminated under conditions to prevent the penetration of flying insects and keep own production workshop.
5. wrinkled
cause:
The thickness of the first layer of gelcoat when brushing is insufficient, the time between brushing the gelcoat (2 times) is too short, the mold or the gelcoat contains moisture during the application of the gelcoat causing poor polymerization gelcoat, workplace humidity is too high or insufficient drying of PVA or too little hardener, slow curing of gelcoat, uneven curing of gelcoat.
The solution:
Apply evenly so that the thickness of the first film is 0.2-0.25 mm. After the gelcoat has fully cured, apply the second gelcoat or topcoat and apply the gelcoat after the mold is dry, dehumidify or stop processing in extreme cases. Let the PVA dry completely then apply the gelcoat. The dosage of the hardener should be between 2.5% and 1%. Increase the workplace temperature and provide ventilation so that no styrene gas remains in the forming mold.
6. demolding
cause:
After brushing the gelcoat, the mold will deform during handling and the local area will heat up. The amount of gelcoat hardener is too large, the temperature difference is too large. Too much mold release coating is not good for cleaning. Left too long after applying gel coat.
The solution:
When handling, be careful not to deform the mold. When heated, the mold should not be placed on the edge of the heat source, so that the temperature difference does not change much. After waxing, buff until bright. Using Release Wax the Right Way After applying the gelcoat, it should be applied within 24 hours.
7. bad shine
cause:
The mold surface is dark, the mold surface brightness is not strong, and the mold is not well processed.
The solution:
Do a good maintenance on the mould, and after a certain amount of production, the mold should be polished again. Each time the wax needs to be polished until it is bright, the wax residue should be cleaned after the wax, the gel coat should be used to make molds and 150# water sandpaper – 2000# should be used to carefully polish, polish, clean and seal molds. Mold post-processing is performed.
8. Bubbles, void air bubbles between gel coat and laminate.
cause:
When applying the gelcoat dirt got in and the surface layer was not thoroughly defoamed.
The solution:
Clean paint tools and molds. Careful defoaming when laying up.
9. uneven color
cause:
Moisture is mixed into the gel coat, sagging (pigment separation) occurs, uneven brushing (the base can be seen through the gel coat), insufficient stirring (the pigment is precipitated in the container). Left too long after stirring the paint. Mixed colors when adding paint
Solution:
Improve the thixotropy of the gel coat, apply evenly (0.3-0. 5 mm), and stir well. When using the added pigment (gel coat), the gel coat in the container should be fully stirred with the glue, and the workplace should be cleaned up when using the gel coat, the warehouse where the gel coat is placed should be clean and tidy
10. Poor curing
cause:
Forgot to add accelerator or curing agent, too little accelerator, poor stirring, styrene gas retention, and low temperature.
Solution:
Before use, confirm whether the accelerator is added. After adding the curing agent, it should be fully stirred and ventilated to volatilize the styrene gas trapped at the bottom and increase the temperature of the work site.
11. scars
cause:
Scratches, wedge wounds, mold release blow injury, mold release agent, wax residue, PVA brush marks, mold scars.
Solution:
Operate carefully, protect the product with soft objects, use the cutting machine correctly, use the demolding method correctly, tap the mold lightly, perform mold maintenance and repair frequently, and apply PVA thinly and evenly.
12. crack
cause:
Reluctant demoulding, unreasonable shape, blow (spider web crack), reluctant assembly, stress concentration.
Solution:
Re-discuss the release treatment method and grade of release agent, mold correction (demoulding slope split die), avoid strong beating, apply the gel coat evenly and not too thick, re-discuss the size of a single product, and re-design the layup plan.
Any fiber glass products/composites/FRP requirements can be contacted by GRECHO to achieve your cost effectiveness.
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Email: info@grechofiberglass.com
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Post time: Oct-21-2022
