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Common problems and solutions of polyurea spraying process

- Aug 30, 2017 -

Polyurea construction process, the main problems may arise: pinholes, drums, curing, stratification and so on.

General problems should be solved in the timely manner when spraying, so as to avoid the late repair of the introduction of other materials or repair caused by new problems, shadow polyurea coating integrity, continuity.

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Pinhole

Pinholes are the most common phenomenon in the construction of polyurea , mainly due to the fact that the substrate treatment is not in place. The substrate is not completely closed, spraying, the reaction heat caused by moisture or air expansion, before the coating curing, the gas burst coating leaked out to form a small pinhole.

For the base surface where the pinhole is prone to occur, after each spray, it should be checked immediately. For a small number of small pinholes, a small amount of polyurea can be sprayed on the cardboard. Before the polyurea is not gel, Will be scraped to the pinhole position, and scraping, and then a whole spray to cover.

For large pinholes, consider reconnecting the area. Or the use of rapid spraying method: thin and fast spray, divided into several times, a film and then spray the next one, which can reduce the heat, thereby reducing the degree of gas expansion.

If the spray construction in the afternoon, but also to a certain extent reduce the emergence of pinholes, because at this time the base surface after sunlight, the temperature increases, the air between the pores greatly reduced. For the late detection of a small number of pinholes can be used to repair the use of polyurea repair materials.

Drums

Drum package is another common problem in the construction of polyurea, mainly due to polyurea coating and base or polyurea coating between the gas or gas caused by, and sometimes in the spraying may occur, more in the spray Within 4-24 hours after the emergence.

The moisture is blocked on the substrate. After the construction, the reaction heat causes moisture or air to expand, forming a certain pressure under the fast curing coating. If the gas leaks out before the coating is cured, pinholes are formed. If the coating is cured Before the gas did not leak out, the formation of small drum package. This is generally caused by poor substrate handling or incomplete curing of the primer.

In addition, under normal circumstances, A, B components through the spray gun, spray to the substrate, can fully react to form a paint film, if the A, B component ratio imbalance, A component over, a component from the muzzle splash or Leakage from the gun to the substrate, the moisture can react with the excess of a components to generate gas, and sealed in the coating, thus forming a drum package.

In the construction found in the drum package, you should cut the drum bag, carefully check the back of the hole, according to the following table to determine the type of drum package, and then solve.

Construction of a long time after the emergence of the drum package is generally due to the high moisture content of the substrate caused by this type of drum area is usually larger, or even flake distribution, cut after the smooth surface, the base surface is generally more humid, sometimes visible Water vapor condensation. In this case, the drum parts should be thoroughly cleaned to ensure that the substrate moisture content is effectively reduced and then repaired.

Poor curing

In addition to the quality of the material itself, the emergence of poor curing is generally due to A, B component ratio caused by imbalance. Usually in the spraying can be found, this time should immediately stop spraying, the curing of the coating completely eliminated, and the use of solvent to wipe, if necessary, construction of a polyurea layer between the lamination agent. Eliminate equipment failure before re-spraying.

Layered

There are two cases of stratification:

A. Polyurea coating is separated from the substrate.

Generally occurs in the substrate processing is poor or the substrate is contaminated. In this case, the coating of the stratified area should be thoroughly removed, the substrate treatment and primer construction should be repeated, then the polyurea is sprayed or repaired with a polyurea repair material.

In addition, the polyurea spray and primer construction time interval is too long, the primer surface wet or dirty may also lead to stratification, this time should be shoveling the stratified area of polyurea layer, the primer surface after grinding and re-construction Paint, and then spray polyurea or use polyurea repair materials for repair.

B. Polyurea coating layer.

The surface repair or maintenance of the coated coating is often caused by this phenomenon, usually caused by spraying intervals for too long or interlayer lamination. In addition, A, B two components of the proportion of imbalance may also cause this phenomenon.

In this case, the layered coating should be shoveled, the surface of the coating can be polished, the stratification by the proportion of the gap may require more thorough removal or cleaning with solvent. And then construction of a polyurea layer between the lamination agent, and then spray polyurea or use polyurea repair materials for repair.


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