Minimum film forming temperature

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The minimum film formation temperature or minimum film formation temperature (MFT) is a term from surface technology and represents the lowest temperature at which a paint is able to form a firmly coherent film . Further terms are the temperature minimum for film formation (TMF), minimum temperature for circulating air and substrate and the English term Minimum Film Forming Temperature (MFFT).

The minimum film formation temperature is important for the formation of a solid, coherent surface from a dispersion (chemistry) . According to DIN 53 787, the minimum film-forming temperature is referred to as the lowest temperature at which a thin layer of a plastic dispersion dries to form a cohesive film. If the MFT is not reached, a cracked film forms. If the white point, which is at an even lower temperature , is also not reached, a whitish powdery layer is formed. Many dispersion coating materials , such as building paints and glazes for outdoor use, must still be processable at temperatures around 0 ° C. The MFT must therefore be close to 0 ° C in order to form a closed surface during drying. The lower the MFT, the lower the temperature at which the dispersion becomes sticky. In practice, this prevents the coating from being applied and should not be below 50 ° C. A good balance between the two properties is therefore necessary. The minimum film-forming temperature can be influenced by film-forming aids and coalescing agents in such a way that it meets the requirements for the respective application.

determination

To determine the MFT, an MFT device, also known as an MFT bench, and a black MFT elevator film are used. First the device and the cooling water of the device are switched on and the desired temperature range (e.g. 5 ° C to 23 ° C) is selected. The coating to be determined is then drawn onto the film in the desired layer thickness and immediately placed on the MFT determination device. Often, to improve the temperature transfer, some diethylene glycol is distributed between the determination surface of the device and the film, so that the film does not slip so easily. The film formation takes place with decreasing temperature from the right 23 ° C to the left 5 ° C on the determination surface. Once the film has formed, the temperature at which a flawless film is present can be read from a scale on the edge of the determination area.

literature

  • Goldschmidt, A .; Streitberger, H. (2002): BASF Handbook Painting Technology , Vincentz Network, ISBN 3-87870-324-4
  • Mischke, P. (2007): Film formation in modern paint systems , Vincentz Network, ISBN 3-86630-898-1