The polymer constituting the emulsion or dispersion generally has a glass transition temperature higher than room temperature. In order for the emulsion particles to be well fused into a uniform paint film, it is necessary to reduce the minimum film formation temperature (MFFT) of the crystallization aid.Film forming agents are a kind of small molecular organic compounds, the film forming agents in the paint film will eventually gradually escape and volatilize most of the film forming agents is an important part of coating VOC, so the less film forming agents should be used, the better.The use of film-forming auxiliaries should give priority to compounds that are not within the VOC limits, but which are not too slow in volatility and have high film forming efficiencies.The amount of coalescent aid depends on the amount of emulsion or aqueous dispersion in the formulation and the glass transition temperature.The amount of the emulsion or water dispersion is large and the Tg of the polymer is high, and the amount of the film-forming auxiliary agent is also large. On the contrary, when the dosage is small, the formulation aid is first considered to account for about the emulsion or the aqueous dispersion. %-5%, or 5% to 15% of the emulsion or dispersion solids.However, for polymer emulsions with Tg over 35  C, it may be necessary to increase the amount of coalescent to ensure the reliability of low-temperature film formation. At this time, the amount of film-forming auxiliary should be gradually increased until low temperature (about 10   C or lower). The coating can form a uniform paint film without cracking or powdering, and find the minimum amount of filming aid.It is not advisable to use a filming aid in an amount of 15% or more of the emulsion or dispersion. It should be considered to replace other filming aids and try again.In addition to lowering the minimum film forming temperature and increasing the density of the film, the filming aid can improve the workability, increase the leveling of the paint, prolong the opening time, and improve the storage stability of the paint, especially the low temperature freeze resistance.

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