Appearance: Light yellow to amber transparent liquid
Solids content (%): >45
Density (25℃): 1.000~1.100g/cm 3
The relationship between surface tension and shrinkage In painting, only when the surface tension of the coating is lower than the critical surface tension of the substrate, can the substrate be wetted and the coating spread on the substrate into a smooth and smooth film. If a paint with a higher surface tension is applied to a substrate with a relatively lower surface tension, the paint will not wet the substrate, and the paint can be applied to the surface of the substrate by mechanical force during construction, but because the surface is not When the coating film is wetted, the surface tension tends to shrink the liquid coating into spherical particles; at the same time, polypropylene wax tip the viscosity of the system increases due to the volatilization of the solvent. If the viscosity has increased to stop the flow before the coating shrinks to form spherical particles, then A very uneven coating film is produced, some areas have no coating film or only a very thin film, while the coating film in the adjacent area is very thick, that is, shrinkage holes are formed. Shrinkage refers to the formation of irregular or non-exposed dents on the coating film, which makes the coating film lose its flatness. From the perspective of leveling, shrinkage is a special “point-type” unevenness phenomenon.
The causes of film shrinkage can be divided into external causes and internal causes.
a. If the shrinkage cavity substrate caused by external causes is contaminated by impurities such as oil, moisture, dust, fingerprints, etc., the surface tension of the contaminated point or area will be greatly reduced, polypropylene wax tip even far lower than the surface tension of the coating. The surface of the treated steel plate and the plastic surface where the release agent is not cleaned, or the critical surface tension of some points or areas is low due to the uneven composition of the substrate surface. After the coating is applied, the points or areas are wet. The film spread coefficient is less than 0, and the wet film will shrink from these low surface tension points or areas to the surroundings to form shrinkage holes. Such shrinkage holes are generally open-bottom shrinkage holes.
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