Analysis of the flow and hanging of water-based paint

Paint film
the paint liquid on the surface of the phenomenon of downward flow is called flow hanging. Appears more vertically or at angular angles. Generally appears on the vertical side for the hanging curtain-like flow, appears at the corner for the tear-like flow hanging
chinese
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problems arise from a variety of reasons - from raw materials, formulations, applications and other stages have a more obvious impact, of which the formulation and application stage of the impact is particularly obvious.
Raw material factors
1
, resin fluidity:
From the point of view of resin mobility, resin particle size is small, solid content is lower, often have better mobility, which also leads to the vertical spray, more susceptible to gravity flowing down.
2
, resin dry speed:
resin dry speed is slower, the paint film is given a longer opening time, which also makes the flow hanging problem more likely to occur.
of course, from the above resin characteristics of the impact of the point of view, most can be adjusted through the formula.
formulation factors
formulation is one of the most important factors affecting the performance of anti-flow hanging. Its effects are mainly reflected in: solid content, viscosity, rheumoid state, drying speed, wetting and spreading.
1
, solid content:
in the case of determining the thickness of the coating dry film, the higher the solid content, the smaller the required coating of the wet film thickness, it is easier to control the paint film in the flow of the limit value below.
2
viscosity: the
viscosity of the air, the better the anti-flow performance.
3
, fluid state:
is different from the viscosity of the intuitive, coatings often show false plasticity, expansion, tentacles and other fluid state.
and tentacles are shown to be better anti-flowing due to their high viscosity in a low shear state.
Because of the rapid recovery of viscosity after the construction of fake plastic state paint, it can achieve considerable film thickness in the construction without flow hanging;
4
, drying speed:
flow hook takes a certain amount of time, and the drying speed is faster, you can make the paint film lose fluidity and prevent the flow hanging before the occurrence of the flow hanging.
in water-based paint, which is closely related to the resin itself, solvent matching, moisture content and construction environment.
, the drying of paint film is also related to the construction method, different construction methods for the drying speed also has different effects. Even the same construction methods, such as in spray construction, different equipment, techniques, etc. will affect the drying speed of the paint film.
5
, wetting and laying:
, such as wetting and wetting, will also affect the performance of anti-flow hanging. Such as the film wetting and laying performance is not good, causing shrink edges, ripples, etc. , the paint film local film thickness increased, more likely to lead to hanging, ripple protruding parts are also more prone to tears.
application factors
the emergence of the phenomenon of streaming is mainly due to the application process. The main factors in the application process are paint, film thickness, spraying techniques, lacquer atomization, construction substrates, construction environment, technology and so on.
1
, paint:
water-based paint in the process of use, according to the instructions, a small amount of water construction. If the water is too much, it is very easy to cause the flow hanging.
2
, film thickness:
paint film thickness is one of the decisive indicators affecting the performance of antiflow hanging. The anti-flow hanging of the paint film, are under the premise of a certain thickness of the paint film, each coating has a certain film thickness limit, beyond this value, it is very easy to produce flow hanging problems.
3
, spraying methods:
the same paint, different users will also have some differences in the issue of flow. In terms of spraying techniques, a small amount of coating of the first shot is much better than a direct wet spray. The atmospheric pressure blows directly to the substrate, and the atomization falls also have different manifestations.
from the construction method, an over-spraying, muzzle distance is too close, the gun speed is too slow, the degree of atomization is not enough, etc. will have a negative impact on the anti-flow performance of the paint film.
4
, lacquer liquid atomization:
coating film is already carried out in the process of spraying. Good atomization, conducive to the uniform spread of lacquer liquid, but also in the spray process has more moisture and solvent volatilization, reducing the risk of hanging.
5
, construction substrate:
different substrate paint capacity has high and low, the more smooth substrate is not easy to paint. Therefore, for different substrate types, roughness, the performance of anti-flow hanging should also be adjusted.
6
, construction environment:
the impact of the construction environment against the flow hanging is mainly achieved through the impact of the environment on the drying time of the coating film. It is well known that the drying speed of water-like paint is greatly influenced by environmental factors. Low temperature and high humidity environment, paint film opening time is extended, is not conducive to paint film anti-flow hanging performance.
7
, process:
to achieve good coating effect, anti-flow hanging performance is one of the inevitable requirements. This performance has a lot to do with the design of the coating process. For example, wet wet process, coating film is not completely dry that is the next construction, etc. , too much pursuit of coating efficiency caused by the flow hanging is not uncommon.
summary
from the above analysis, the factors affecting the performance of anti-flow hanging are many.
formulation engineers in the
design
formulation should be considered in all aspects, as far as possible to achieve a wide range of adaptable anti-flow hanging performance, such as seasonal, construction equipment, construction environment caused by different flow.
Of course, sometimes formula engineers in order to balance other performance, can not meet the anti-flow hanging performance under harsh conditions, it is necessary to cooperate in the application process, such as reasonable process matching, control of paint film thickness, improve the construction environment.