How to avoid the "tweezers" problem in coating? These 6 tricks must-see!

For most coating engineers, coating "tweezers" is a very headache, today, let's deeply analyze the "tweezers" this "ghost worry".
the formation of "tweezers"
"tweezers" is a layer of dense small bubbles formed inside the coating film, the coating film protrudes a small dot, forming a needle tip large or more atmospheric bubble shape.
some of the spacing is small, dense and hemp presentation, some of the sparse spacing, can intuitively appear the shape of the bubble, which is caused by uneven coating film, usually appears when the coating film to dry

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how to solve the problem of tweezers? Let's continue to look down
avoid using slow-drying solvents!
to solve the problem of "tweezers", you can choose to extend the drying time, that is, extend the opening time of the paint film. The addition of slow-drying solvents can effectively extend the drying time of the paint film, which is helpful to prevent the "tweezers".
But the addition of too much slow-drying solvent, will lead to solvent evaporation rate is much lower than the paint film table dry speed, but not conducive to solving the "tweezers" problem, and may even appear hanging, dark bubbles and other more serious problems.
that is, slow-drying solvents are not actually lmnary and measures should be taken to balance the drying time of the paint film with the evaporation rate of solvents, moisture and air.
you can try solvent aid!
to solve the problem of "tweezers", we can consider the choice of solvent assistance. However, in the selection, there are the following points to note:
(1) to consider solvents can not contain isocyanate reactions with water, free acids and alcohols and other substances, can not choose alcohol ethers and high water content solvents.
(2) according to the changes in the construction environment to adjust the ratio of solvents, to obtain a better volatility rate, to give the paint the best flow.
(3) it is possible to increase the opening hours of the paint film to ensure that the coating is mixed with bubbles, water and solvent vapor before the coating table is dried. High boiling point solvents can be selected, but attention needs to be paid to the blocking effect of strong polar solvents on HDI.
the resin and curing agent
in general, we will choose the equivalent ratio of 1.2 to 1.5, the resin and curing agent combination. In addition, the compatible between resin and curing agent can be improved, and the selectivity of reaction can be improved.
of additives
we usually add silicone substrate moisturizers and leveling agents to formulation modulation.
But many silicone additives on the stirring construction process produced bubbles have a stable effect, the surface pressure is reduced more stable foaming, and easy to float to the coating surface and closed the film surface, so that the film solvent is difficult to release, so that the gas in the coating film aggregation and the formation of small bubbles, easy to form "tweezers" or dark bubbles.
therefore, under the premise of meeting wetting and leveling, try to choose a low stability foam tendency of the additive. In addition, it can be combined with a suitable de-foaming agent to avoid the formation of bubbles or the formation of bubbles as far as possible to eliminate.
construction conditions
15 to 35 degrees C for the best construction temperature, in addition to the relative humidity should be adjusted below 75%, to avoid high temperature and humidity, direct sunlight construction.
spraying, to the substrate should be flat, clean and non-polluting, can not have dust and other impurities, spraying amount to the appropriate amount, construction environment requirements non-polluting, less dust.
preparation of the paint, to use 200 purposes of the filter cloth filtration, filtration after static 10-20min, as far as possible to eliminate small bubbles in the paint before the construction, and to ensure that the construction during the reification period.
in order to reduce pinhole production, generally after painting into the drying room, to ensure that the wet paint film has about 10min solvent volatility time (called flash drying time or leveling time).
summary
above, we can combine the above 6 methods to reduce the occurrence of the phenomenon of "tweezers", so that it can better play the role of paint decoration and protection.
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