exterior paint durability Construction relations

1 exterior paint durability
1.1 weatherability and color retention
Decorative function is one of the important features of the exterior paint. Cultured Stone Veneer Exterior paint is long-term exposure to the outdoors, by the wind, rain and sun, after a period of time, the appearance of finishes chalking, discoloration, discoloration, loss of light and other phenomena. The weathering of high-performance exterior paint color retention requirements generally 8 ~ 10a, the equivalent of a national standard artificial accelerated aging 1000h, and its color is not greater than 2. Coating chalking, fading and discoloration and coating binders and pigments are closely linked.
(A) Binders and weatherability and color retention
The base material plays a decisive role in the performance of the paint. External finishes by ultraviolet light, the sun and the rain will progressively deterioration, which ultraviolet impact. It enables the base polymer chemical reaction and deterioration. If the emulsion polymer containing a polyethylene, polyacrylate, polymethacrylate, polystyrene, polyvinyl chloride, poly (vinyl acetate) and poly-butadiene, etc., by ultraviolet radiation, it is prone to the main chain scission, intermolecular cross linking or degradation reactions.
So that the binder polymer for crosslinking or degradation will cause changes in coating properties: intermolecular crosslinking makes extended reduced, while the main chain will reduce the strength of the coating, eventually leading to the yellowing of the exterior paint or powder technology. Note that the base material in the preparation of high performance exterior paint should preferably therefore, select the excellent weathering resistance of the emulsion as a binder. Silicone modified acrylic emulsion and water emulsion polyurethane is the fastest growing and the most the coating binders variety of development prospects. Higher chemical bonds between the polymer molecules of these binders and special molecular structure determines they have excellent anti-aging properties, its artificial accelerated aging more than 1500h, some even up to 3000h, fully able to meet the high-performance exterior paint on Binders weatherability requirements. Of course, the emulsion weather resistance not only concerned with the varieties And it is also the size of the emulsion particles in the emulsion and emulsifying system closely related. Emulsion finer particles, the coating film formed by the more perfect, the more excellent weather resistance corresponding. Furthermore, still in the emulsion by adding a certain amount of an ultraviolet absorber, can reduce the UV damage of the coating film.
(2) pigments and weathering protection color
Paint coating by the base material polymer and the Yen (fill) material. Therefore, the types and ratio of the two kinds of main component determines the structure and physical properties of the coating film. In the coating formulation, when the pigment volume concentration (PVC) is below the critical PVC, pigment particles dispersed in the base polymer continuous phase to form the "sea - island" structure; but if the PVC exceeds the critical PVC base polymers the gaps between the pigment particles can not be completely filled with loose accumulation of pigment particles, voids therebetween, the coating scrub resistance, contamination resistance, weatherability, a sharp decline. Similar emulsion varieties, PVC is lower, the higher the gloss, weathering resistance, color retention worse. So, in the preparation of high performance exterior paint should strictly control PVC less than the critical PVC as far as possible, to ensure the integrity of the coating.
The primary role of the pigment is to make the coating film has a certain degree of opacity and show different colors, so to make the coating film has excellent weather resistance, a pigment on the need to have good hiding power and coloring power, the higher the degree of dispersion, sharp The color and light stability. The white pigment excellent weather resistance, not only their own color consistent, and can absorb large amounts of ultraviolet light, to mitigate the damaging effects of ultraviolet radiation on the base material or other color pigments that improve weatherability of the coating color retention. White pigment, the most widely used, and the best of rutile titanium dioxide. Color pigments, inorganic and organic pigments are used, but the coating film weathering performance considerations, the general use of inorganic pigment is more suitable. The light resistance and weather resistance of the inorganic pigments are generally superior to organic pigments, present in the exterior latex paint, the main use of the excellent weathering resistance of the iron-based pigment.
In addition, in the high-performance coated should avoid using easy powder filler, and filler has better weather and pH stability. Better application precipitated barium sulfate, quartz powder, mica and wollastonite powder.
2.2 stain resistance
China's industrial smoke, excessive dust and vehicle exhaust emissions, high dust content in the air, and less per capita green area. Therefore, high stain resistance exterior paint adapt to this special state of the environment is extremely important practical significance.
High stain resistance performance of the exterior paint is very important. Exterior paint slowly, an important reason for this is the stain resistance of the coating is not ideal, the decorative effect is short-lived. Therefore, the need to address an important issue for the high-performance exterior paint is to try to improve the coating anti-stain resistance coating of contaminated medium resilience. Coating anti-contamination and poor performance of the main reasons are: ① the coating preparation process generally required the use of emulsifiers and a variety of additives, with the passage of time, in the coating of these low molecular weight substances to be volatilized, so that the coating left in a large number of pores. The microstructure, compared with solvent-based paints, latex paints and coatings containing a large number of micropores, and the surface is relatively rough, exhibit uneven. Atmospheric dust is easily deposited under the effect of gravity which, to different degrees of covering of the coating color. When it rains, the dust along with the rain capillary action penetrated coating, evaporation of water, dust particles continue to be retained in the pores, "fatal" impact this will have on the decorative effect of the coating.
Therefore, increasing the density of the coating, hard is an important way to address contamination issues. I have developed a sol-acrylate emulsion organic-inorganic composite coatings, anti-stain determination, its reflectance decreased only about 5%, mainly due to the sol colloidal particles are relatively subtle, the particle size is generally 5 ~ 40nm, the structure after the film formation is very compact and hard, the gap is minimal, dust particles easily penetrated therebetween. Add nanoscale SiO paint can improve the hardness of the coating to dramatically improve the ability of anti-staining. ② binder, the organic polymer chain structure determines the polymer emulsion coating prone to the accumulation of static electricity, thereby generating the electrostatic adsorption, dust particles are easily adsorbed at the surface of the coating, the decorative effect of the coating, the emulsion polymer chain covalent bond (e.g. Si-O) of the introduction of some of the ionic inorganic conductive properties, can be improved to avoid electrostatic adsorption pollution of the coating. ③ Since the coating high temperature return YS, easy, dust, resulting decorative effect decreased, generally high hardness coating stain resistance, which requires a high glass transition temperature (Tg) of the emulsion, but the coating film at the same time constructability disadvantage. Cultured Stone Veneer
Strictly speaking, the paint just a semi-final purpose coating on the surfaces of buildings, buildings from the decorative and protective role. Therefore, the dry film coating after construction is finished. Coating durability play supporting construction technology have a close relationship, in order to obtain a satisfactory long-term effects of finishing, it is necessary to strictly control the construction engineering quality of the paint.
Usually due mainly out powder coating defects caused by improper construction methods of exterior paint, peeling, efflorescence, shedding. In order to avoid the emergence of these quality defects, should be strictly in accordance with the the coating construction engineering specifications for construction. For cement grassroots should pay special attention to control moisture and alkalinity. Accordance with the regulations applying emulsion paint, the moisture content shall not be greater than 10%; concrete base material curing period should be more than 28d, cement mortar plastering should be more than 14d, grassroots pH control in less than l0; surface should be cleared before construction dust, oil, etc., to maintain the cleanliness of the surface of the grass-roots level; sealing primer before coating porous substrates should be brushing a layer of latex or solution type, to avoid the suction of the substrate on the coating uneven, causing flooding.