972 water-based adhesion promoter has good compatibility with commercially available polymer emulsions such as: acrylic emulsion, VAE emulsion, polyvinyl acetate emulsion, polyurethane emulsion, neoprene emulsion, natural rubber emulsion, styrene-butadiene emulsion and tackifying resin emulsion, and has good heat resistance, oil resistance, UV resistance, and acid and alkali resistance.
For high-quality coatings, the amount of film-forming substance emulsion used in the formulation is relatively large, and the pigment volume concentration is lower than the critical pigment volume concentration. Latex paint is a typical coating with thermoplastic polymer as the main film-forming substance, so the film-forming substance has a key influence on the physical properties of the coating. At a certain temperature, the film hardness of a thermoplastic polymer is mainly determined by the glass transition temperature (Tg) of the polymer. As the glass transition temperature increases, the hardness of the obtained film increases. The domestic architectural coating polymer T is generally designed at 10~25℃. When the external environment temperature is higher than the glass transition temperature of the emulsion, the coating will become soft and sticky, and dust particles will easily adhere to the surface of the paint film, resulting in stain resistance.
Decrease in dirtiness. The scanning electron micrographs in Fig. 20-10 show the paint film of paints with less than the critical pigment volume concentration under different magnifications. The black cavity area in Fig. (a) is the emulsion polymer filled between the pigment and filler particles, and Figure (b) shows the dust particles adhering to the surface of the paint film. The glass transition temperature of the latex coating film-forming substance is an important factor affecting the stain resistance of the paint film. Numerous experiments have found that increasing the glass transition temperature of the emulsion can effectively improve the stain resistance of the paint film. However, as the glass transition temperature of the emulsion continues to increase, the coating film will tend to crack. At the same time, in order to ensure sufficient emulsion under construction conditions For film formation, the amount of film-forming auxiliary is increased accordingly, which delays the establishment of the early hardness of the paint film. When a harder covering polymer is added, it can replace part of the emulsion, increase the hardness of the coating film, and improve the stain resistance.
For economical paints with PVC greater than the critical pigment accumulation concentration, 3m dyneon ptfe dispersion there are voids on the surface of the paint film [Figure 20-11(a)]. Small pollutants (5~30jm) invade into the coating with rainwater. After the water evaporates , The pollutants will stay in the paint film and form permanent pollution. When a covering polymer with a spherical shape and a small particle size is added, it can be filled in the above-mentioned cavity. Although it is impossible to fill it completely, the gap at this time is far smaller than the size of the dust. From the image magnified 100 times, the paint film is quite dense, and it is difficult for dust to adhere to it. This is also the reason why the covering polymer can make the coating feel smooth. The latest covering polymer product of Rohm and Haas is R opaque TM. The average particle size contributes well to stain resistance.
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