First choose high-quality mold gel coat. As the surface of the mold, the gel coat of the mold requires the surface after curing to be dense, with certain strength and hardness. However, due to the influence of the resin matrix of the gel coat, the added auxiliary materials, quality control, etc., the final product quality indicators such as leveling, defoaming, viscosity, and deformation resistance of the gel coat are very different. The layers produce different defects. Such gel coats have higher requirements on the skills of operators during construction, which is reflected in the fact that on-site personnel must make corresponding adjustments according to the actual situation during construction. A high-quality mold gel coat should be a spray gel coat with low viscosity, high thixotropy, good defoaming and leveling properties, and stable curing characteristics.
Secondly, the curing system of the gel coat is also one of the factors that easily cause pinholes. Disproportionate accelerators and initiators will remain in the gel coat after the gel coat is cured, and pinholes will form when the gel coat surface is demolded. Excessive curing system or high temperature can easily shorten the setting time of the gel coat, so that the air brought in during the application of the gel coat cannot overflow in time, resulting in a large number of micro bubbles in the gel coat. Form a pinhole. When the amount of gel coat is small, it is easy to cause disproportionate or excessive addition due to measurement errors. Therefore, it is recommended to use pre-accelerated gel coat. The proportion of accelerator added is accurate, the gel time is relatively stable, and the stirring accelerator is reduced. Is the number of bubbles introduced.
In the construction of gel coat, the surface of the model, the operating environment, the operating method, etc. will also lead to the appearance of pinholes to varying degrees. First, as the mold-product model of the mold, the surface quality will directly affect the surface quality of the mold. Loose and rough surfaces are not conducive to the formation of a good gel coat surface. Due to the looseness, the large surface area of the rough surface will be detrimental to the discharge of tiny bubbles during the construction of the gel coat.
Improper construction method of gel coat will also cause the generation of pinholes. Spray gel coat is less likely to produce pinholes than hand brush gel coat. The main spray gel coat has low viscosity, uniform spray construction thickness, easy to control, and is more conducive to the discharge of bubbles . When spraying, it should be carried out in time after the release of the model surface is completed to avoid contamination of the coating layer. When spraying, the first layer of the first pass should be thinly sprayed, with an interval of 1-2 minutes between each layer, which is beneficial to the gel coat. The bubbles in are discharged. When the viscosity of the mold gel coat is too high, it is best not to use solvents (styrene, acetone) for dilution. The small molecules of the solvent will evaporate to form bubbles.