Research on special matching primers for elastic coatings on exterior walls

Elastic coating as a category of high-performance coatings on the outer wall, due to the composition of its raw materials, determines the advantages and disadvantages of such products are quite prominent. Elastic emulsion contains a large water absorption rate of the monolith, so the water resistance of elastic coatings is generally poor, the performance of water blistering, peeling and even bottom peeling and other phenomena, especially in the humid and rainy southern regions. In order to solve this common problem, this paper solves the above problems by changing the matching of elastic coating system and developing a special primer special for elastic coating.
Expicturement
With the rapid development of the construction industry, the requirements for the decoration and protection of the exterior walls of the building are getting higher and higher, because the walls are directly exposed to the natural environment, the building is affected by temperature difference, sunlight, rain, wind and sand and other harsh conditions, the walls are prone to aging, cracking and other phenomena, destroying the aesthetics of the building, accelerating the damage to the walls, greatly shortening the life and safety of the building. And as a wall outside the direct protection against the harsh environment of the building "skin" - paint, play a direct role in protecting the wall.
In China, the proportion of elastic coatings used on the exterior walls of buildings is increasing, according to market statistics in 2014, the use of elastic coatings on the exterior walls of buildings accounted for nearly 60% of all flat coatings, compared with only about 20% in 2009, elastic coatings have become the main use of building exterior materials.
elastic coating is based on synthetic resin emulsion, and pigments, fillers and additives prepared, applied a certain thickness (dry film thickness is greater than or equal to 150 m), with the micro-cover due to substrate telescopic (movement) produced by the small elastic functional coating. The advantages and disadvantages of elastic coating relative to ordinary flat coating coating are obvious, the advantage is that because the elastic exterior paint film has a high elongation rate, so when the wall appears small cracks, the paint film is stretched deformation but will not crack damage, can still maintain the original barrier effect, thus avoiding the cracked wall directly exposed to the atmosphere. However, the water resistance of elastic coatings, especially the initial water resistance has always been its short board, the exterior wall for a long time in the rain, humidity and other environment, especially after construction in a short period of time, it is easy to foam, peeling and even peeling phenomenon, seriously affecting the decoration and protection function of the building. See Figure 1
of elastic coatings, especially the initial water resistance is poor, has been a short plate of elastic coatings. Compared with ordinary coatings, elastic coating drying speed is slow, paint film soft, paint film breathability is poor, water molecules and elastic paint film ester bond hydrogen bond binding, thereby destroying the original primer and finish between the force, resulting in elastic paint encountered water easy and primer peeling, foaming, peeling and other phenomena.
The traditional coating system of supporting primers, only pay attention to the penetration and closure of the grass roots, and the grip of the opposite lacquer layer is not very concerned, this elastic coating system for a long time in a rainy, high-humidity state, will cause the primer layer and paint layer separation. In order to solve the common problem of the above-mentioned elastic coating, the development of a primer with good adhesion to both the substrate and the coating layer is the key to solve the defect of elastic coating.
experiments, starting with the reverse grip of the primer, to solve the water resistance problem of the elastic coating support system. We cooperate with well-known domestic emulsion companies, through technological innovation, developed a special elastic matching primer emulsion (hereinafter referred to as 'special emulsion'), with this emulsion made of primer, not only on the grass has a strong permeability, adhesion and self-compaction, but also with elastic paint chemical bond riveting, so that the binding key between the coating can not be hydrolysis in a high humidity state, so that the whole system to achieve excellent water resistance, for the elastic coating system provides a good solution.
test
the use of ordinary exterior primer formula, the selection of different types of emulsions, test elastic matching system water resistance.
test results of 4 different primer matching systems in Table 1 are found in Table 2. Experiments show that the elastic system with special primer is water resistant, while the elastic system with ordinary primer is very water resistant (see Figure 2).
Experiments and Results Discussion
In order to further study the effect of emulsion use on the performance and supporting effect of primer itself, respectively, the gradient test was carried out, the above formula was selected, and the amount of emulsion added in the formula was set at 25%, 30%, 35%, 40%, 45%, according to JG/T210-2007 "building interior and exterior wall paint" standard and supporting bullet system test, the results are shown in the table 3.
3 experimental data show that when the amount of emulsion is 30% or more, the primer performance meets the requirements of JG/T210-2007 "Primer for interior and exterior walls of the building" exterior wall II standard (see Table 4), while the amount of emulsion used to 35% or more, the primer performance meets the JG/T210-2007 "Building interior and exterior wall primer" exterior wall Type I standard requirements (see Table 4). Combined with performance and cost factors, we choose to take 35% of the amount of emulsion formula as a matching primer.
selected 2 kinds of commercially available primers, compared with this experiment special primer,
test primer performance and supporting elastic coating system performance.
From Table 5 can be seen, ordinary primer and elastic paint matching, dry adhesion is very good, but after the water matching ordinary primer and elastic paint adhesion are very poor, outdoor testing is also poor, and this experiment dedicated matching primer are very good.
laboratory plate test water resistance comparison
maintenance and test conditions: roller coated with a primer on an asbestos-free cement plate, to be primer maintenance 24h after the use of wire rod two-way film elastic paint (120um) 80um), two surface paint interval 3h, after the completion of the second paint film maintenance 24h after immersion, immersion area of 2/3 of the plate surface, observe the immersion 3d rear plate condition, see Figure 3.
. Supporting adhesion contrast
plate conditions: roller coated with a primer on an asbestos-free cement plate, to be primer maintenance 24h after the use of wire rod two-way film elastic finish (120um plus 80um), two paint interval 3h.
adhesion: paint maintenance 72h after the rowing method test matching adhesion.
water adhesion: immersion 8h take out the model dry after normal temperature maintenance 30min, rowing method test supporting adhesion.
second adhesion: immersion 8h to remove the model drying after normal temperature maintenance 24h, the rowing method test supporting adhesion.
4 is a commercially available primer and special primer adhesion, immersion adhesion, secondary adhesion results comparison.
. Construction wall comparison
experimental conditions and methods: selected processed cement wall roller primer, maintenance 24h roller coating 2 elastic paint, two surface paint interval 3h, paint maintenance 24h after a lot of water (preferably directly Before the rain weather will be completed the above-mentioned substrate construction, directly through the rain experiment; after the completion of the water (or rain) lightly keyed paint film surface, can easily tear the paint is unqualified, Figure 5 is the commercially available primer and special primer construction wall comparison results.
Conclusion
This test, through preliminary screening of emulsion types, determined that the use of special emulsion matching elastic system, can solve the problem of poor water resistance of elastic coating system, and then by determining the use of primer emulsion, in order to achieve the best cost-performance balance point. Compared with the commercially available ordinary primer, the excellent effect of this product is verified from the performance of the primer, the water resistance performance of the matching elastic paint system, and the outdoor effect of the matching elastic paint.
This experiment solves the disadvantage of water resistance of the elastic building coating on the outer wall, improves the adhesion of the opposite layer of the primer by using special emulsion, makes the matching primer not only have excellent permeability and denseness, but also has the special two-way rivet structure of the primer emulsion, which can be closely combined with the elastic paint. As a whole, weaken the elastic coating hydrolysis in high humidity environment, so that the substrate layer, primer layer, elastic paint layer combined into a more solid whole, to achieve excellent overall water resistance, completely solve the problem of poor water resistance of elastic coatings, for the large use of elastic coatings provides a good solution.
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