Film-forming additives and their applications in latex paint coatings (2)

2 The influence factors and performance characteristics of film-forming additives
To study the effects of film-forming additives on emulsion coatings, it will be of great help to understand and grasp the film-forming process of water-based coatings in depth and detail, to improve the film-forming properties of coatings, reduce the dosage of film-forming additives, and to develop environmentally friendly coatings such as low VOC or zero VOC. From the film-aiding process, the film-forming additive provides sufficient free volume in the film-forming process to deform the polymer particles and the polymer molecular band diffusion, winding and fusion into a continuous membrane. According to the theory of free volume, the amount of film-forming additives can be estimated by formula. However, the reality is that different film-forming additives on the same emulsion to reduce the minimum film-forming temperature is different, it is clear that the other properties of film-forming additives also have a significant impact. The application practice found that the water solubility, compatibility and volatility of film-forming additives affect the presence, movement behavior and use effect of film-forming additives in coatings.
film additives act like a "temporary" plasticizer to reduce the polymer Tg, once the particle deformation and filming process is completed, the film additives will evaporate from the coating film, so that the polymer Tg value is restored to the initial value. Usually most film-forming additives are volatile at room temperature with a lag of 1 to 2h from water, so film-forming additives should consist of solvents with slower volatility. The biggest prerequisite for film-forming additives is that during the drying process, the moisture-volatile film additive remains in the coating and eventually evaporates itself from the coating. Propylene glycol butyl ether as a membrane additive for water-based coatings, it is good for ethyl propylene latex paint, phenyl-propylene latex paint effect, plus 4% of the emulsion can make the minimum film temperature of water-based coatings from 20 degrees C to about 4 degrees C.
film-forming additives affect the drying speed of the coating film to a certain extent, and the film-forming additives significantly affect the minimum film-forming temperature and corrosion resistance of the coating film. Film-forming additives can also deform polymer latex particles at low temperatures to form a complete continuous film that reduces water and corrosive ion migration to the surface of the material. If polymer latex particles congenate into a sethylated membrane under capillary pressure, the permeability of the coating film increases, thus reducing corrosion resistance. The addition of film-forming additives is generally 3% to 11% is appropriate, otherwise the polymer latex particles gather prematurely, making the coating surface porous and loose. Excessive film-forming additives are also important factors affecting the stability of coating freeze-thaw. Film-forming additives promote the plastic flow and elastic deformation of latex particles, change the properties of co-polymers, and can be filmed over a wide construction temperature range. To choose the best quantity, we should consider that latex paint can have excellent film-forming, better leveling and anti-hanging resistance, but also make latex paint good frozen solubility. In addition to helping film-forming properties, film-forming additives also have the function of reducing the freezing temperature of latex paint, which is beneficial for the normal construction of latex paint at lower temperatures.
film-forming additives help to improve the scrub resistance and decontamination of their coatings by increasing the degree of denseness of the paint film. Film-forming additives promote effective film-forming agents, in the composition of film-forming additives must have both hydrophobic film-forming additives and hydrophobic film-forming additives, because the use of these two film-forming aids has the synergy of promoting film-forming. Hydro-hydroplasty aids migrate to the hydro-hydroelectral shell of emulsion particles, playing the role of plasticizers, promoting the first effective binding of hydro-water-based shell parts of emulsions, and triggering the initial polyglytic membrane. After that, the process of polyfilm formation is promoted by hydrophobic film-forming additives. Because hydrophobic film-forming additives have a greater affinity to the hydrophobic nuclei of emulsion particles and migrate to the nuclear part, thus effectively plasticizing the nucleation part, so that emulsion particles further variant, forming a structure. When a single hydro-hydroelectral film aid is used, only the shell part of the emulsion particle is plasticized, although it begins to form a membrane, but cannot be carried out to the second stage. And when the use of insufficient amount of a single hydrophobic film aid, only make the particle's nucleation process can not start normally, but if the use of excessive single hydrophobic film aid, then the nucleation of emulsion particles can reach a higher degree of plasticization, although the initial clustering membrane is bad, but the second stage of the film process can still occur, but also form a good water barrier emulsion film. However, hydrophobic film-forming additives have a greater impact on the stability of emulsions, with the increase in their dosage of the impact of increased, easy to cause emulsion milk breaking, condensation and other phenomena. This is because the dehydration of hydrophobic film aids destroys the hydration protection layer of emulsion particles and makes the stability of emulsions less stable.
a product to be used as a film-forming additive, must meet certain requirements. First of all, this product used as a temporary plasticizer must have sufficient chemical stability, for example, will not be saponified in alkaline formulations. Second, the smell should be small, in the indoor use of coatings have such requirements. Then there is the requirement that membrane additives to be compatible with these sensitive polymer dispersants, added without instability.
the characteristics of film-forming additives should be: film-forming additives are a volatile temporary plasticizer, can promote the plastic flow of latex particles and elastic deformation, improve their cohesion, can be filmed in a wide range of construction temperature range. The ideal film-forming additive should have the following characteristics: film-forming additive product boiling point is high, environmental protection performance is superior, good solubility, low volatility, easy to be absorbed by latex particles, can form an excellent continuous coating film. As an excellent solvent of polymer emulsion, it can reduce the minimum film-forming temperature of the polymer, has a small solubility in water, has a certain volatility, the film-forming process can be stuck in the coating film to play a role, after all the film-forming volatility, does not affect the performance of the coating film, does not affect the stability of the emulsion. Film-forming additives can reduce the minimum film-forming temperature of latex paint, make emulsion particle deformation easier, improve the degree of emulsion particle condensation, emulsion polymer and pigment between wetting, mechanical properties of latex paint film, latex paint film density, latex paint wash resistance. When the amount of film additives is less, increasing the amount of latex paint can significantly improve the wash-resistant brush performance of latex paint, with the increase of film-forming additives, latex paint wash-resistant performance improvement effect is reduced.
there are many kinds of coating products on the market, wall coatings, waterproof coatings, water-based color paste and many other characteristics and components are not the same, this stability is more attention. Instability can be observed from a significant increase in viscosity, or the most serious case is the occurrence of gels, the same reason, operation should also be very careful to prevent the occurrence of local vibration reactions, that is, gel occurrence.
film-forming additives are used in latex paint excellent performance of film-forming substances, can greatly improve the film-forming properties of latex paint, not only for pure propylene, phenylamphetamine, acetate emulsion is also effective. In addition to significantly reducing the minimum film temperature of latex paint, it can also improve the polygene, weather resistance, scrubbing and color display of latex paint, so that the paint film at the same time has good storage stability..