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 These are GENERAL guidelines. For different problems or more information, contact ITWC, Inc. Toll Free 1-888-489-2462. |
| Problem | Cause |
|---|---|
| Reactivity too fast, quick gel |
Prepolymer abuse from overheating, processing temp too high, excessive catalyst in curative |
| Reactivity too slow, long gel & demold time |
Processing temp too low, mold temp too low, curative temp too low, off ratio, poor mixing, inadequate catalyzation |
| Prepolymer viscosity too high | Prepolymer abuse from overheating, processing temp too low, moisture in prepolymer |
| Change in NCO – lower than reported | Moisture in prepolymer, prepolymer abuse from overheating, beyond shelf life |
| Parts too soft at demold | Material temp too low, poor mixing, off ratio, molds too cold, inadequate catalyzation |
| Shrinkage & shrink marks | Mold temp too low (peak exotherm too far above mold temp) |
| Wet spots (uncured material) |
Poor mixing, unmixed resin or solvent contamination, machine malfunction |
| Bubbles or pin holes in finished product | Moisture in extender, entrained air at mix, insufficient degassing, pouring technique |
| Fissures or fold marks in finished parts | Filling mold too slowly, gel time too fast, excess mold release, excessive amounts of mold release |
| Cracks | Material selection and/or mold design – contact ITWC, Inc. |
| Striations | Machine malfunction, poor mixing, inconsistent material temps |
| Skins and solids present in prepolymer | Exposure to moisture |
| Overall poor appearance of finished parts | Process temp too low, mold temp too low, poor mixing, dirty molds, contaminated material/mold release |
| Poor Adhesion | Excessive amounts of mold release, contamination in mold before or after application of adhesive, improperly applied |
| Parts stick to mold | Poor mixing, insufficient amount of mold release, dirty mold, very high mold temp |
| Spongy parts (parts soft at demold but harden as they cool) |
Mold temps too high |
Phone: 641-528-3000 • Fax: 641-528-4041
• Toll Free: 888-ITWCINC (489-2462)