Becoming two-phase pigment paste, after application in dilute resin:
We are producing a light-ivory pigment composite part and after mixing light ivory-pigment paste with the resin and styrene, the yellow and black pigments that make up the light ivory-pigment paste are separated after 20 to 30 minutes. Please advise us of the cause of this problem.
This problem may have occurred for the two following reasons:
• The usage percentage of pigment paste consumption might be higher than the recommended amount. Please note the correct dosage of consumption is listed on the back of the pigment paste packaging.
• To use the pigment paste in diluted resin, you can increase the viscosity of the resin by adding some fumed silica. Regarding your problem, since the pigments that make up the shade colors are separated from each other and the pigments with a higher density than the resin are at a lower level and those with a lower density are at a higher level and the color becomes two-phase.
In general, the use of styrene in resins is not recommended, as it reduces the thixotherapy properties of gelcoat, which allows the separation of different pigments in a mixture.
Gel coat surface does not cure due to high humidity:
We have used ISO gelcoat with spray viscosity in shipbuilding in Bandar Abbas area. Unfortunately, due to the high humidity in Bandar Abbas, this gelcoat does not cure completely and its surface remains sticky. Please help us solve this problem.
For optimal curing of gelcoat in humid areas, using a general cobalt accelerator may not achieve the desired result, since cobalt is a type of salt and does not work well in humid areas. Therefore, it is better to use a special type of cobalt for humid areas due to the very high humidity in the air of Bandar Abbas, or use DMA along with cobalt for curing assistance.
Also cover the surface of the part with a layer of Melinex (thick plastic) so that during curing time, the surface of the composite part does not come in contact with moisture and oxygen and the curing of gelcoat is done completely.
Light paint defect of composite part:
We are a boat manufacturer and we use pigment paste to produce self-coloring composite boats. Lately, the color of the pigment pastes have been faded on the boat surface. What could be the reason of this problem?
According to the photo, it seems that the occurred problem of the composite boat is not pale. The reason is that gelcoat has not been applied evenly and uniformly, so in some areas due to the thin surface of the gelcoat, the underlying layer is visible and has a pale-like appearance. Also, to build a boat, it is recommended to use isophthalic gelcoat or resin, which is more resistant to UV and humidity, and never use styrene for dilution.