General knowledge of coating: the function of film forming assistant

Core tips: latex paint is a large category of water-based paint, which contains low VOC and belongs to "green paint" Emulsion paint is mainly a mixture of water dispersions of polymer particles and pigment particles But they do not have good construction performance, so it is difficult to get good paint film It is necessary to add various additives to achieve the required construction performance and film-forming quality, and film-forming additives are one of the most important additives in latex paint 1 Film forming mechanism of latex paint The film-forming process of latex paint is complex, and it needs to go through a polymer from dispersion Paint knowledge how about Akzo Nobel Powder Coating Recommended introduction: powder coating is a kind of coating with different form from general coating, which is in powder form It is a new type of coating, because of its own advantages and more and more known by people Let's introduce Akzo Nobel Powder coating Akzo Nobel Powder coating is a cost-effective coating solution, which can be applied to different kinds of products After the treatment of static electricity and fire baking, a tough and durable coating surface will be formed, with the least impact on the environment Since the introduction of this technology, powder coating has been able to continue to maintain the Paint Home News: latex paint is a large category of water-based paint, containing very low VOC, belonging to the "green paint" Emulsion paint is mainly a mixture of water dispersions of polymer particles and pigment particles But they do not have good construction performance, so it is difficult to get good paint film It is necessary to add various additives to achieve the required construction performance and film-forming quality, and film-forming additives are one of the most important additives in latex paint 1 The film forming mechanism of latex paint the film forming process of latex paint is complex, which needs to go through a process from dispersed polymer particles to coalescence into a whole After the construction, the moisture volatilizes and the spherical particles must fuse with each other to form a continuous coating The film forming process of latex paint is as follows: (1) the particles gradually close to the spherical particles in the latex paint to keep the dispersion state with the function of double electric layer and shielding stability After the construction of film forming, the water gradually volatilizes Depending on its driving force, the dispersed particles gradually close to each other When approaching a certain degree, the adjacent particles tightly squeeze together to achieve the dense state, Lose the freedom of movement and form gelatinous form (2) The stability of particles destroys the water further volatilization, and the volume of paint film shrinks When the evaporation of water will be exhausted, the driving force will also disappear At this time, the capillary force obviously plays a role The volume shrinkage and capillary absorption force are far greater than the dispersion and stable repulsion of particles, and the stability of particles is destroyed, so that particles contact, attract, flow and coalesce with each other to form a continuous film (3) With the passage of time, the residual additives gradually evaporated, the polymer molecular segments penetrated each other, the membrane properties gradually improved, and finally formed a uniform and good performance film 2 the concept of film forming AIDS and the commonly used film forming AIDS latex paint polymer are thermoplastic polymers Only at a certain temperature can they form the film and form the lowest temperature of continuous coating, which is called the minimum film forming temperature, so the film forming temperature must be at the lowest film forming temperature In order to achieve a certain function of latex paint, the proportion of hard monomers added is large, and the minimum film forming temperature is higher than room temperature, so film-forming assistant must be added to make it film-forming Film forming assistant, also known as film forming agent, agglutinating agent and coalescing agent, is usually a high boiling point solvent, which volatilizes slowly after the film is formed, promotes the plastic flow and elastic deformation of latex particles, and improves their coalescing performance In the latex paint, the film builder softens the surface of the particles because of the dissolution of the latex particles, so that the polymer particles are easily compressed and deformed The addition of the film forming auxiliaries can reduce the minimum film forming temperature of the emulsion and the latex paint Commonly used film-forming auxiliaries include glycol, propylene glycol, hexanediol, methylganglion, dodecarbon acetate, monoethylene glycol, propylene glycol ether, ethylene glycol butyl ether, propylene glycol butyl ether, ethylene glycol ether, acetic acid vinegar, turpentine, dipentene Terpinene, dehydrocai, etc 3 Selection of film forming AIDS (1) the film forming AIDS must be strong solvent of polymer, which can reduce the glass transition temperature of polymer and have good compatibility, otherwise it will affect the appearance and luster of paint film (2) the solubility in water is small, which can have excellent coalescence performance for the absorption of latex particles (3) the film forming AIDS have appropriate volatilization speed and remain in the latex paint coating before film forming, Its volatilization rate should be lower than that of water and ethanol After the film is formed, it must be completely volatilized (4) added to the latex system and then adsorbed on the surface of the latex particles, without affecting the stability of the latex particles 4 The function and influence factors of the film forming assistant is like a kind of "temporary" plasticizer, which is used to reduce the glass transition temperature (TG) of the polymer Once the particle deformation and film forming process are completed, the film forming assistant will volatilize from the film, so as to restore the TG value of the polymer to the initial value In general, most of the film-forming aids are 1-2 h later than water at room temperature Therefore, the film-forming AIDS should be composed of solvents with slower volatility As a film-forming agent, the biggest prerequisite is that during the drying process, the water volatilizes, while the film-forming agent remains in the coating, and finally it volatilizes from the coating itself Propylene glycol butyl ether as film forming aids for waterborne coatings showed that propylene glycol butyl ether had better effect on acrylic emulsion paint and styrene acrylic latex paint The minimum film forming temperature of waterborne coatings decreased from 20 to 4 degrees by adding 4% of emulsion Film forming AIDS directly determine the degree of polymer latex particles agglomerating into a complete and continuous coating, and then affect the long-term anti-corrosion effect of the coating To some extent, the film forming assistant also affects the drying speed of the film The minimum film forming temperature and anti-corrosion performance of the film are obviously affected by the film forming assistant Film forming aids such as low temperature can also make polymer latex particles deformation and fusion, forming a complete continuous film, which can reduce the migration of water and corrosive ions to the steel substrate surface If polymer latex particles aggregate to form discontinuous film under capillary pressure, the permeability of the film increases, thus the corrosion resistance decreases In general, 3% to 11% of the additive is suitable, otherwise the polymer latex particles coalesce prematurely, making the film surface porous and loose Excessive film-forming additives are also important factors affecting the freeze-thaw stability of coatings Home of coatings is specialized in coatings, diatom mud, paint coating, coating technology, fire retardant coating news and coating, diatom mud, paint coating, coating technology, fire retardant coating decoration knowledge and decoration renderings,