Selecting the wrong UPR grade causes laminate failure, poor surface finish and costly rework. Use these three parameters to decide:
| Grade | Viscosity | Gel Time | Best For |
|---|---|---|---|
| EP-909 | 80-90 sec | 10-12 min | Fiber Doors, Hand Lay-up |
| ORTHO-919 | 60-80 sec | 5-9 min | RTM, Pultrusion, Boats |
| ISO-989 | 80-90 sec | 10-12 min | Chemical Tanks, Marine |
| EP-955 | 60-80 sec | 5-8 min | Plywood, Wood Coating |
| ISO-998FR | 130-180 sec | 10-20 min | FRP Panels, UL94 V-0 |
| EP-929 | 85-90 sec | 5-6 min | Quartz Stone, Solid Surface |
| EP-979 | 80-90 sec | 10-12 min | Cultured Marble |
| EP-9000 | 75-95 sec | 3-5 min | Automotive Putty |
💡 Rule of thumb: For RTM/pultrusion target gel time <9 min and viscosity <80 sec. For casting with filler >150 phr, choose solid content >65% and acid value ≤20 mg KOH/g. All grades tested with 0.33% Cobalt Naphthenate + 1% MEKP at 30°C.
