Coating knowledge: what properties should a good primer have?

Core tip: the primer is directly attached to the substrate, on which there is a surface coating or intermediate modeling coating, which plays a connecting role A good coating system has no layer interface between the layer and the coating film The primer is the first coating attached to the substrate, so the quality of the primer is required to be very high The primer should have good water resistance, alkali resistance, waterproof, isolation of salt and alkali exudation (anti pan alkaline, anti salting out), as well as good adhesion and interlayer adhesion (1) Alkali resistant cement mortar used in building exterior wall and putty with cement composition Paint agent, top 10 Chinese wall paint brands Recommended introduction: interior wall paint and exterior wall paint can achieve beautiful, clean and pleasant effects, but the effects in different environments are different, so the color of the paint will be different There are ten brands of Chinese paint, ten brands of global paint, ten brands of Chinese wall paint, and ten brands of Chinese paint, Famous trademark of Chinese paint and coating In private rooms, most of us choose according to our own personality, personal hobbies and living habits The younger generation will choose the interior wall paint with rich colors and bright colors, while the older ones will have some working experience Paint Home News: primer directly attached to the substrate, which is attached with surface coating or intermediate modeling coating, plays a connecting role A good coating system has no layer interface between the layer and the coating film The primer is the first coating attached to the substrate, so the quality of the primer is required to be very high The primer should have good water resistance, alkali resistance, waterproof, isolation of salt and alkali exudation (anti pan alkaline, anti salting out), as well as good adhesion and interlayer adhesion (1) The cement mortar used in building exterior wall and the putty for exterior wall with cement composition are all materials with high alkali resistance The primer is often directly applied on the surface of these materials The primer film has good alkali resistance, which can ensure that the primer will not be damaged by alkali saponification in the long-term use process, which is the key to ensure its sealing performance and adhesion (2) Anti pan alkaline pan alkali refers to the white alkaline substance on the surface of concrete or mortar The appearance of this phenomenon is closely related to the chemical reaction to form the concrete's firmness The hardening process of cement is the chemical reaction of water and calcium silicate to form Ca (OH) 2 and calcium silicate hydrate There are also sodium silicate and potassium silicate in cement, so NaOH and KOH will be produced in the hydration process of cement The performance is to protect the finish paint from the basic substances from the wall materials, which may cause discoloration, chalking, loss of light and other defects, so as not to affect the decorative effect of the finish paint (3) The phenomenon of salting out resistance is one of the important reasons for the white and blooming of the film The salting out and pan alkali are often crossed The hydroxide produced in the process of cement hydration reacts to form carbonate and water when it migrates to the substrate surface and contacts with C02 in the air The carbonate will be left on the substrate surface after the water volatilizes When the primer is not used or the primer is not used properly, the carbonate will precipitate into white particles on the coating, which is more significant on the coating of dark paint, resulting in the film blooming In addition, in the finishing engineering, especially in the north, there is often a phenomenon of rushing for the construction period In order to cope with the handover, additives (mostly salts) that are higher than the standard requirements are often added With the evaporation of water in the base layer, salts will be brought out and detained on the surface of the coating, causing the coating to blossom The performance index is mainly to protect the finish paint, so as to prevent the soluble salt from the wall material from being brought to the wall by rainwater to become white crystal substance, which will affect the decoration effect of the finish paint (4) Low water permeability this performance index is related to the pan alkaline resistance and salting out resistance of the paint film The lower water permeability makes the rain water can not enter the primer film, so the soluble salt and alkaline substance in the wall will not be brought to the surface of the top coat, so as to protect the top coat Generally speaking, among the single component primers, the oil-based transparent primer has the best water permeability, followed by the oil-based white primer The waterborne transparent primer is related to the water resistance of the emulsion itself (5) Workability this performance refers to the performance that primer can be applied to different new / old walls smoothly through different construction methods Roller coating is the most common construction method of exterior wall primer In the practical engineering application of primer, some primers are difficult to be applied, which may lead to the phenomenon of granulation and binding of the roller and brush of the roller in the process of construction, thus affecting the uniformity of the coating (6) Good interlayer adhesion The primer is generally connected with the intermediate coating between the cement mortar layer and the top coat or the intermediate coating between the putty layer and the surface coat This requires considering the adhesion between the primer and the relatively loose base material, and meeting the adhesion between the primer and the relatively dense top coat Therefore, the primer must have good adhesion between layers to ensure its own sealing performance and the long-term use of the top coat Performance This is relatively easy for the white primer with pigments and fillers, as long as we pay attention to the product mix, there will be no problem; but for the transparent primer, we need to pay attention not to apply the primer too thick, so as not to affect the adhesion of the top coat on the primer 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,