Classification of pigment fillers for coatings

Color fillers for coatings can be divided into 4 categories: color pigments, effect pigments, rust-proof pigments and fillers.

1g[D(W;) T/D(T+AT)] =CAT/(Cz+△T)(18-4) where T-—temperature, K;
D(W)——The diffusion coefficient when the temperature is T and the amount of film-forming aid is W;
C, C2-constant.
AT is defined as the plasticizing effect that promotes the diffusion of polymers. Obviously, adding a film-forming aid is equivalent to providing free volume, thereby providing conditions for the inter-diffusion and permeation of polymers, and finally achieving the result of film-forming.

Requirements for film forming aids
In fact, the film-forming assistant is a polar solvent with high boiling point, low glass transition temperature and very slow volatilization that is added to latex paint to help polymer film formation.

High film-forming ability
The film-forming aids are required to have high film-forming properties. A polymer has its own characteristic T value due to its different composition and structure. This polymer emulsion also has an MFT value corresponding to its ?, value. If a film-forming aid is added to this emulsion, the effective film-forming aid — water and surfactants will also affect the Tg of the latex polymer system and will affect the minimum film-forming temperature of the latex paint. Of course, Tao can be calculated from equation (18-1) by water, but some people believe that the MFT of emulsion polymer is lower than Tg due to the plasticizing effect of water. The T including the plasticization of water is regarded as MFT.

K=MFT/T, (18-2) where K=0.92~0,98.
Combining formula (18-1) and formula (18-2), considering Vp=1-V, we get [,1/MFT=V.[(wT, -Ta) /(KT g, Te)] + 1/(KT g) (18-3) In the formula V,-the volume fraction of the film-forming aid in the formula.
Plotting 1/MFT vs. V, is a straight line. According to Hoy’s research, it is also a straight line when the amount of film-forming aid is less than 5g/100g of dry resin.