Specialized additives for epoxy, polyester and composite resin that improve key material properties: curing, viscosity, sanding, surface finish and reinforcement. In practice, the main selection criterion is the intended use of the mix, whether for laminating, finishing, filling or board repair.
At Mundo-Surf you’ll find different composite additives used in the manufacture of surfboards: PMEC catalyst for polyester resin, waxed styrene to make sanding easier, styrene monomer to reduce viscosity, glass microballoons and mineral fillers to adjust consistency and provide reinforcement. There are also additives designed to accelerate curing, limit bubble formation and improve the final finish. When choosing a format, take into account: total mix volume, working temperature and the required dosing accuracy.
For polyester resin to harden properly, the usual ratio is between 1% and 3% of PMEC catalyst. What really makes the difference here is the ambient temperature and the total mass of resin prepared.
If there is only one thing to remember, it is this: do not exceed 3%, as this can cause yellowing and compromise the finish. The most stable working range is usually between 16 °C and 25 °C.
The usual dosage is approximately 5% of waxed styrene in the mix. In practice, it is used so that the final coat cures with a surface suitable for sanding.
What separates a correct application from one that will cause problems is the timing of its use: this additive is designed for finishing, not for laminating. It makes sanding easier and helps achieve a more uniform surface, without prematurely clogging the sandpaper.
This is not a product defect. When temperatures drop, bear in mind that below 14 °C it may thicken or turn semi-solid, even with small visible particles.
The key factor to decide whether it is still usable is how it recovers when the container is shaken. Just shake until it returns to a liquid, homogeneous state.
