Paint knowledge | eight Application Mistakes of polyurethane waterproof coating

Core tip: polyurethane waterproof coating (JS waterproof coating for short) has been rapidly developed and widely applied from the end of last century to the beginning of this century due to its good physical properties, simple construction methods and construction on wet base However, in recent years, this kind of product has appeared a great potential quality hazard, which left a very bad impression on many construction units and management departments and began to hold a skeptical attitude Less than ten years after the new product came out, it has been faced with the awkward situation of being accompanied by the inferior eliminated products, which is regrettable The reason is that in addition to the low price competition in the market, the manufacturer intentionally sacrifices the quality and does not supervise the construction process To let go of work and materials 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 Home of coatings: polyurethane waterproof coating (JS waterproof coating for short), with its good physical properties, simple construction method and construction on wet base, has been rapidly developed and widely applied from the end of last century to the beginning of this century However, in recent years, this kind of product has appeared a great potential quality hazard, which left a very bad impression on many construction units and management departments and began to hold a skeptical attitude Less than ten years after the new product came out, it has been faced with the awkward situation of being accompanied by the inferior eliminated products, which is regrettable The reason is that in addition to the low price competition in the market, the manufacturer intentionally sacrifices the quality and does not supervise the construction process In addition to the excessive use of work and materials, it is also related to the improper application of this product and many people in the industry have misunderstandings about this product 1 The basic principle of JS waterproof coating is to modify inorganic cementitious materials with cement and quartz sand as the main components by synthetic polymer latex The film formed by JS waterproof coating keeps the characteristics of high strength and strong water resistance of cement cementitious materials and improves its flexibility (i.e elongation) as much as possible At the same time, the polymer latex also brings about negative effects, that is, the decrease of hardness and the decrease of long-term water resistance and aging resistance The size of the negative effects is closely related to the type and dosage of the latex used (that is, the modification ability of the latex) At present, there are two main types of latex used in JS coating on the market: polyacrylate latex and polyethylene vinyl acetate latex The modification ability of the former is better than that of the latter, and the amount of the former to achieve the same performance is significantly less than the latter, and its negative effect is also significantly less than the latter However, most people mistakenly think that JS coating should be based on the greater the amount of latex, the better When choosing products from different manufacturers, the same price should be taken as the criterion to compare which factory has the larger amount of latex Therefore, in order to show the large amount of latex, some manufacturers or businesses mix the purchased latex raw materials with water to prepare JS coating The product quality is far from the real JS coating What's more, some construction teams use the commercially available polyvinyl acetate latex (commonly known as white latex) or polyvinyl alcohol glue after contracting the waterproof project at a low price (commonly known as 107 glue) mixed construction, its consequences can not be described, seriously damaged the reputation of JS coating At present, less than 10% of JS coatings used in construction projects actually use polyacrylic latex, which is the main reason why JS coatings have slipped into the ranks of "inferior" products 2 Insufficient understanding of classification and use The elongation of JS waterproof coating is directly related to the amount of latex, but the amount of latex directly affects the long-term water resistance of the coating In order to solve this contradiction, the technical treatment of engineering specifications and product standards is to divide JS coating into two types, type I is the large amount of latex, and the elongation is required to reach more than 200%, which is used for engineering parts with intermittent immersion (such as To meet the requirements of large deformation Type II is the engineering part (basement, toilet and bath room, etc.) with a small amount of latex and a elongation of only 80% to meet the requirements of long-term water resistance, but it is not used separately in many projects From basement to roof, one type is used Type I or type II not only fails to achieve the expected effect, but also has many potential quality problems, which is disappointing 3 The relationship between the coating thickness and the construction times no matter how good the waterproof coating is, it must have a certain coating thickness as the quality assurance In the roof engineering technical specifications and underground engineering waterproof technical specifications, the basic thickness of JS coating is required to be 1.5-2.0mm However, in the actual engineering design and construction monitoring, we often only pay attention to the construction times but ignore the final thickness of the coating We often see that some design drawings only indicate "several coats of JS waterproof coating" but not the thickness requirements The site management only cares about painting several times To some lack of integrity of the construction team to drill a hole, the coating water diluted, than the design requirements for one or two times more than the approval of the site management personnel, after contracting to the project at a low price can earn a lot of profits, no matter how excellent the performance of the product can not withstand such damage 4 The importance of neglecting the influence of the mixing state on the film performance JS coating is a two-component product, in fact, the last process of product production - mixing and phase separation is left to the site construction team to complete Who knows, the mixing and phase separation state of two-component products is very important for the formation of film performance In addition, JS coating is not as easy as the mixing and phase separation of other liquid-liquid two-component products for powder liquid two-component Although the product specifications of various manufacturers have explained the correct method of site mixing, many construction teams are perfunctory in the mixing process, some even do not have a special mixer, on-site Find a stick and mix it by hand A few people know the judgment and mastery of "end point of phase separation", which greatly reduces the performance of the final formed film due to incomplete mixing of phase separation 5 Misunderstanding of tensile strength In the product standard of JS coating, the tensile strength of coating film is required to be type I ≥ 1.2MPa and type II ≥ 1.8MPa respectively Many people mistakenly think that the higher the tensile strength is, the better In fact, in the test method of tensile property of JS coating, there is a process of heating and curing at 50 ℃ for 24h after 7 days of standard curing Many coating products are caused by the volatilization and migration of plasticizer during 50 ℃ thermal curing The rapid growth of tensile strength indicates that the thermal aging properties of these products change rapidly and their service life is not long Therefore, the products with abnormally high tensile strength should be alarmed If necessary, the heat aging retention rate test can be done It is not unilateral that the higher the tensile strength is, the better 6 In order to avoid the stress concentration, the tire base is added to expand the dispersed stress and reduce the cracking of the coating Therefore, the setting of the tire base position directly affects the use effect It should be that the closer the tire base is to the base, the more stress can be dispersed In fact, many projects set the tire base position at will, no one cares, in order to set it in the middle of the coating Some projects lay the tire base on the surface of the coating The author once found this phenomenon in a construction site and asked why the construction personnel exposed the tire base On the surface, the workmate replied, "we will settle the money of the tire base with the employer", which is ironic 7 One sided understanding of "construction at wet base" Compared with other waterproof coatings, JS waterproof coating can be constructed on wet base There is a problem of moisture degree here, which does not mean that it can be constructed under any humid climate or very high moisture content of base Because latex in JS coating is solidified by volatilization, high moisture content of base and too humid climate are unfavorable for the curing of latex to form film, which will reduce Low film elongation At the same time, the cement in JS coating is hydrated and solidified The base course and climate conditions that are too dry are unfavorable to cement solidification Therefore, during construction in hot and dry seasons, it is necessary to spray some water on the base course before construction In fact, JS coating has some requirements for the construction temperature and humidity range Generally, the temperature is 5 ℃ ~ 35 ℃, and the humidity is 50% ~ 70% Regardless of the temperature and humidity conditions, forced construction can also form film, but the film performance is far from each other 8 Misunderstandings about the water can be mixed most manufacturers in their product instructions that water can be added to dilute the paint during the first brushing construction, so as to improve the penetration of the base and improve the adhesion of the base Therefore, many people misunderstand that JS coating can be added with water at will, which is very harmful The ratio of two components in JS coating - the ratio of polymer to cement and the ratio of water to cement (the ratio of water to cement) are determined by the manufacturer through many tests The effect of changing one component ratio on the performance of the coating film is great In the actual project, the amount of powder can be increased at will The phenomenon of adding water to adjust the consistency is everywhere In fact, many projects use the name of JS coating to reduce the material In this way, JS coating has little future 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,