These are GENERAL guidelines. For different problems or more information, contact itwc.

Reactivity too fast, quick gel	Prepolymer abuse from overheating, processing temp too high, excessive catalyst in curative
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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
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Prepolymer viscosity too high	Prepolymer abuse from overheating, processing temp too low, moisture in prepolymer
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Change in NCO – lower than reported	Moisture in prepolymer, prepolymer abuse from overheating, beyond shelf life
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Parts too soft at demold	Material temp too low, poor mixing, off ratio, molds too cold, inadequate catalyzation
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Shrinkage & shrink marks	Mold temp too low (peak exotherm too far above mold temp)
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Wet spots (uncured material)	Poor mixing, unmixed resin or solvent contamination, machine malfunction
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Bubbles or pin holes in finished product	Moisture in extender, entrained air at mix, insufficient degassing, pouring technique
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Fissures or fold marks in finished parts	Filling mold too slowly, gel time too fast, excess mold release, excessive amounts of mold release
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Cracks	Material selection and/or mold design – contact ITWC, Inc.
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Striations	Machine malfunction, poor mixing, inconsistent material temps
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Skins and solids present in prepolymer	Exposure to moisture
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Overall poor appearance of finished parts	Process temp too low, mold temp too low, poor mixing, dirty molds, contaminated material/mold release
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Poor Adhesion	Excessive amounts of mold release, contamination in mold before or after application of adhesive, improperly applied
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Parts stick to mold	Poor mixing, insufficient amount of mold release, dirty mold, very high mold temp
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Spongy parts (parts soft at demold but harden as they cool)	Mold temps too high
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For safety information on all our products please visit the Literature Library.

 

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