The minimum film forming temperature is the lowest temperature that is required to coalesce a polymer that is applied to a substrate into a thin film. The minimum film forming temperature of a polymer is extremely important to know and understand when applying a coating to avoid a coating failure.
If the polymer is applied to a substrate and the temperature is less than the minimum film forming temperature then it may not cure properly and the coating typically cracks. This does not occur if the minimum film forming temperature is met or exceeded.
While it may be possible to approximately determine the minimum film forming temperature of a given polymer coating through calculations, one of the best ways to measure it is by using a minimum film forming temperature bar, which is a device consisting of a platen and a heating element. The material to be analyzed is applied to the platen in a very thin layer. Then the minimum film forming temperature bar platen heats the material. The temperature is recorded when coalescence occurs.