What is the minimum film forming temperature of the emulsion? What is the determining factor? How to measure?

The lowest temperature at which a polymer emulsion can form a continuous transparent film is called the lowest film-forming temperature, usually expressed by MFT. The lowest film-forming temperature of emulsion is an important application index of emulsion. That is, below a certain temperature, after the water in the emulsion evaporates, the polymer particles are still in a discrete state and cannot be integrated. Therefore, the emulsion cannot form a continuous and uniform coating film due to the evaporation of water; At a specific temperature, after the water evaporates, the molecules in each polymer particle will permeate, diffuse, deform, and aggregate to form a continuous transparent film. By measuring the minimum film-forming temperature of the emulsion, the performance and construction quality of the emulsion and latex coatings can be judged.

The MFT of the emulsion is determined by the internal structure of the polymer particles and the glass transition temperature.

There is no quantitative relationship between the MFT of the emulsion and the Tg of the polymer. Generally speaking, when Tg is high, MFT is also high. Generally, the composition of the prepared polymer emulsion is relatively uniform inside the particles. In this case, the MFT and Ta are roughly the same. But there are many exceptions, the reason is that MFT is affected by factors such as surfactants, protective colloids and water in the emulsion. Polymer T. The relationship between MFT and MFT varies with the polarity of the monomers used. For polymers with large monomers, the MFT of the emulsion is lower than Tg, and for polymers with low monomers, the MFT of the emulsion is It is higher than Tg.