The presence of moisture in polyurethanes is the greatest cause of failure or performance loss in coatings and sealants. Moisture can react with isocyanate to form gaseous carbon dioxide, leading in turn to bubbling, pinholing and other defects.
Moisture contamination can occur either from within the formulation or as result of excessive atmospheric humidity. Solvents may contain traces of water which can lead to precipitation of urea crystals. Similarly, pigments, fillers and flatting agents can contain absorbed moisture which forms carbon dioxide gas on reaction with isocyanate. This carbon dioxide is then entrapped within the film surface – particularly so in high solids formulations – causing pinholes or bubbles. As well as detracting from the surface appearance of the coating, these defects can also produce significant reductions in performance characteristics such as chemical and abrasion resistance.
The presence of water in one-component moisture cure polyurethanes leads to poor in-can stability. Similarly, moisture in isocyanates results in the production of CO2 which dissolves in the product and can subsequently cause foaming when the container is opened. In more acute cases, containers may begin to bulge and lids burst as a result of excessive vapour pressure.
When two-component urethane coatings are applied under highly humid conditions, there is a tendency for the isocyanate to react preferentially with atmospheric moisture. This isocyanate/water reaction produces microbubbles on the surface causing loss of gloss and hazing. Moisture on the substrate surface can also create CO2 pockets or pinholes.
Incozol 2 – Moisture Scavenger
Incozol 2 is an oxazolidine that is intended for use as an effective moisture scavenger in urethane coatings and sealants. It can be used to eliminate residual moisture from solvents, polyols and prepolymers and also from plasticisers and pigments.
Incozol 2 has a low toxicity rating and hydrolyses on exposure to moisture, yielding reactive hydroxyl and amine groups.
Features & Benefits
• Eliminates CO2 bubbles and pinholes in two-component systems
• Minimises downglossing and hazing under high humidity application conditions
• Improves gloss, abrasion resistance and chemical resistance
• Prevents gassing and gelling in one-component moisture cure systems
• Fully reacts into urethane polymer matrix
• Excellent handling properties
Typical Applications
Incozol 2 is suitable for use in one- or two-component systems. It is not generally recommended in one-component paints or sealants with a low NCO content as the residual amino alcohol reacts with the isocyanate during storage, reducing the reactivity of the system and leading to retarded drying times.
When added to the polyol side of a two-component system, Incozol 2 removes residual moisture from the formulation preventing bubbling and downglossing.
Incozol 2 is not stable in blends with aromatic isocyanates.
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