Q: We build high-performance composite skateboards (bamboo sandwiched between fiberglass/epoxy), and we’re looking for two things:
- A non-toxic or low-toxicity sealer for the edges and bottom surface of the board; should be clear or amber
- Non-toxic or low-toxicity finish to act as a grip surface on the top of the board
It also needs to be flexible and durable.
We currently use a water-based urethane dispersion for both, with a silica aggregate for the grit surface. Any help or thoughts would be appreciated.
A: Powder coatings, which are non-toxic by their nature, can be applied to composites. A number of issues need to be considered with this process.
The composite board probably does not have sufficient conductivity to electrostatically spray powder onto its surface. Therefore, a conductive preparation will have to be applied to the board prior to powder coating. I can provide you with a few options if you wish.
The next issue is identifying a powder coating that can be applied and cured at temperatures low enough to avoid distorting the board or causing volatiles to evolve from the composite. Some low-temperature powders can be cured around 250°F for around 20-30 minutes. If your composite remains intact under this condition, then I would pursue this option.
If 250°F is too high, you can consider using UV-curable powder coatings. This technology allows you to process powder coatings in the range of 200-250°F. Using these products will require a low-temperature melt phase, followed by exposing the warm powder surface to intense UV energy. The UV is generated by specially designed lamps that are commercially available.
The advantage of the UV process is much lower operating temperatures and a much shorter curing cycle. The melt phase typically takes 2-8 minutes, and the UV step requires a couple seconds.
Both the low-temperature-cure powder and UV-cure material can be formulated in clear or amber appearance. A grip surface can also be formulated using silica or other inert material.