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Applications & Uses
- Applications
- Recommended Applications
Although POLYCOR® 99C gel coats are formulated as low VOC products, it should be noted that overatomization of a gel coat means more volatilization (more overspray, more monomer and solids loss, more odor). It is important then to strive for good atomization (good fan pattern, no fingers or tails, uniform particle size of about 1/16²) while maintaining lowest pump and atomizing pressures as practical.
The inherent chemistry of these gel coats does not allow for the same ease of fluid movement experienced with other gel coats. Adjustments may have to be made for pump pressure, delivery rate, tip size and atomization. Polynt Composites does not recommend fluid lines longer than 50 feet, or pumps smaller than 20:1 ratio. In addition, 99C’s are more sensitive to cold temperatures than are other gel coats. POLYCOR® 99C’s are formulated for airless as well as conventional spray application. Neither brushing nor rolling is recommended. Refer to Polynt’s Composites Applications Guide (Cookbook,Conventional Gel Coat–Spray Equipment) for equipment recommendations. For best results these high performance coatings require careful application procedures. Poor application will quickly negate the beneficial properties of these gel coats. Refer to Polynt’s Composites Applications Guide (Cookbook,Conventional Gel Coat–Application). Polynt Composites recommends a gel coat delivery rate of no more than 2.5 pounds per minute with conventional air atomized equipment, and no more than 4 pounds per minute with airless equipment.
For optimum results, uniform catalyst mix must be achieved. Even with the equipment properly calibrated, potential problems can occur due to poorly atomized catalyst; surging problems (gel coat or catalyst); poor tip alignment (catalyst to gel coat mix); contamination; and poor application procedures, which will quickly negate all benefits of calibration. The equipment (and application procedures) must be monitored on a routine basis to ensure proper application and cure of the gel coat. Inquire about and adhere to all equipment manufacturers’ recommendations. For best overall end performance properties, a wet film thickness of 18 ± 2 mils is recommended as ideal.
Films less than 12 mils may not cure properly, may be hard to patch, have more print-through, and be more susceptible to water blisters. Films above 24 mils may pre-release, trap porosity, crack and are more subject to weathering discoloration.
In addition to the low VOC chemistry, the lower viscosity and thixotropic index result in both less overspray and less monomer loss, but the total film thickness should be sprayed in multiple passes (at least 3 at 18 mils, 4 at 20 to 24 mils). More rapid film build could result in some sag.
Proper mold maintenance is important. Although 99C’s have excellent patching properties, minimal repair work is always desirable. Sanding and compounding can hasten the chalking and loss of gloss of all gel coats. Avoid overspray settling on mold surfaces by beginning the spray pattern closest to the vapor/air exhaust and progressing to the opposite mold end. Maintain recommended spray distances from the mold surface.
Properties
- Color
- Typical Properties
| Value | Units | Test Method / Conditions | |
| Thixotropic Index (2/20) at 77°F | 4.5-7.0 | — | — |
| Sag Resistance at 77°F (Good) | 20 | mils | — |
| Flash Point at 77°F | 82-88 | °F | — |
| Weight per Gallon at 77°F (depending on color) | 10.0-11.5 | lbs | — |
| Viscosity Brookfield RVF, spindle #4 at 4 rpm at 77°F | 15000 | cps | — |
| Viscosity Brookfield RVF, spindle #4 at 20 rpm at 77°F | 3400 | cps | — |
| Gel Time (depending on product) at 77°F in 100g mass | 10-18 | minutes | — |
| Hide at 77°F (Complete) | 10 | mils | — |
| Tack Free/Dull Gloss Time | 60-90 | minutes | — |
| Adhesion Time | 4 | hr | — |
| Solvent Wipe Time | After overnight cure, slight color may be removed_x005F but surface will remain tack free | — | — |
Technical Details & Test Data
- Cure
It is recommended that gel time be checked in the customer's plant because age, temperature, humidity and catalyst will produce varied gel times. All data referencing gel or cure refers specifically to ARKEMA Luperox® DDM-9 catalyst. United Initiators Norox® MEKP-9 and Norox® MEKP-9H, Akzo Nobel CADOX L-50a and CADOX D-50 are expected to yield similar performance. Arkema Luperox® DHD-9, United Initiators Norox® MEKP-925 and Norox® MEKP-925H, and Pergan HP-90 may yield slightly shorter gel and cure times.
The catalyst level should not exceed 3% or fall below 1.2% for proper cure. Recommended range is 1.2% to 3.0% with 1.8% at 77°F being ideal. Normally, the gel coat film is ready for lamination in 30 to 45 minutes. This time element is dependent on material temperature, room temperature, humidity, air movement, and catalyst concentration. Special fast-cure versions are available upon request. Fast-cure products have shorter stability and should not be inventoried over 45 days.
These products should not be used when temperature conditions are below 60°F, as curing may be adversely affected.
Storage & Handling
- Handling and Storage
Uncatalyzed, 99C Series gel coats have a shelf life of 120 days when stored at 73°F or below, in a closed, factory-sealed, opaque container, and out of direct sunlight. Fast cure 99C Series gel coats (gel time less than 9.0 minutes) have a shelf life of 60 days. For both standard and fast cure products the shelf life is measured from date of manufacture. The shelf life is cut in half for every 20° over 73°F. Totes of product can have even shorter shelf life (66% of that for drums).