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| What is the function of a coalescing aid in waterbased paints? |
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| The coalescing aid acts as a temporary plasticizer in latex emulsions. The coalescing aid lowers the glass transition temperature (Tg) of the latex polymer. As the paint dries the polymers that have been softened by the coalescing aid are allowed to flow together and form a film after the water has left the system. Since coalescing aids are volatile, they evaporate out of the film. This allows the polymer to return to the original Tg therefore giving harder films for better block and print resistant coatings. Plasticizers are sometimes used in latex paints, but they do not allow the polymer to return to its original Tg, since they do not evaporate out of the coating, therefore the polymers remain soft and tacky which can cause poor block and print resistance.
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