Antifouling Paints

The intent was to:

1. Blend Zonyl® micropowder together with today's antifouling paints.
2. Coat test samples.
3. Subject test samples to ocean environment for four months.
4. Subject test samples to Scrub Resistance Test (ASTM D2486) after four months.
5. Reduce clean-up time and effort at the end of the boating season ( Table 1).

After establishing one of the most popular paints used today (Interlux Bottomkote paint #669 Blue), test samples were prepared. Micropowder blends started at .5%, 1.0% and then increments of 5% to 20% blend by weight. Zonyl®  micropowder grades MP1100, MP1200, and  MP1300 were used inclusively.

Zonyl®  MP1100 did not mix well in the 20% blend without adding 1.5% thinner solvent (Interlux #355 vinylux solvent) to the formulation. A two blade stirrer, angled at 30°, was used to blend the samples in a clockwise motion. All blends were made at 2200 rpm for three minutes. The total blend size was 50 grams.

Clear acrylic plaques were chosen as a sample base because of gelcoat surface similarities. Each sample measured 4" x 12" x 1/8".

Two l/2" holes were drilled at one 4" side.

The surface of the samples were cleaned with Freon® 113. Application of the micropowder paint blends onto one side of the samples was completed using a #20 metering rod. The other side was brush painted by hand using a 1" horsehair brush. A new brush was used for each sample. All samples were air cured for 24 hours before subjecting to testing. It was noted that when applying the micropowder paint blends to the test samples, the Zonyl®  MP1200 (with 20% solids) went on smoother and easier than the 20% blends of Zonyl®  MP1100 or Zonyl®  MP1300.

It was determined that the samples should be subjected to a real-life environment to determine if any actual benefit occurred. A floating sample support was designed for this purpose. A rectangular box frame was made using pine 2" x 4" lumber. The frame measured 2' x 3'. Stainless all thread jungle gym 3/8" frame was used as rods. The rods were run through the framework in l/2" drilled holes and secured with stainless steel nuts, bolts and washers. This created a sample holding rack. All metal surfaces were coated with Rustoleum blue enamel. A second coat of Interlux Bottomkote anitfouling paint #669 blue was then applied to all surfaces, both metal and wooden.

The samples were suspended from the framework by running two rods through each sample. One inch surgical tubing was put on the rods to separate each sample. There were 10 samples hung from each row. Two rows were fitted into the framework. Styrofoam was used as an additional floatation aid. It was attached to the wooden frame with galvanized nails. The nails were then painted with Interlux Bottomkote #669 Blue antifouling paint.

The University of Delaware College of Marine Studies at Lewes, DE was selected as the test location for following reasons:

1. Higher plant and animal growth occur in shallow salt water because of higher temperatures.
2. The site and position would allow an average 8-10 hours sunlight in a 24 hour period.
3. Security is good.
4. Water maintains a minimum 4' level during tidal activity.

The samples were positioned in the water such that one-half of the surface area was exposed above water and half was submersed below water. The initial water temperature was 14.5°C. This was the lowest water temperature measured. The study was completed 143 days later at the same low temperature of 14.5°C. The highest water temperature recorded was 26°C. The floating platform was removed every two weeks for 10 minutes to photograph the samples for growth content and to insure the devise was secure.

The samples were removed from the rack and stored in sea water at room temperature for one week before testing. The ASTM D2486 scrub-resistant test was performed on all samples. It consisted of a small scrub brush moving in a left to right motion at a constant rate and pressure. All micropowder blends showed positive test results. Table 1 lists the number of scrubs necessary to produce a clean sample. Zonyl®  MP1100 at 15% and 20% blends required the least number of scrubs to produce a clean sample.

Conclusions

1. All DuPont micropowder blends with antifouling paint showed a positive test result.
2. The higher concentrations of Zonyl® MP1100, MP1200, and MP1300 had better test results.
3. Zonyl® MP1100 has good potential as an additive in antifouling paints at 15-20% blends because of the best test results.

Table 1: Number of Scrubs Necessary to Produce a Clean Sample