Evaluation of the Resistance to Cracking of Paint and Varnish Coatings

The method of assessing the crack resistance of coatings is discussed in this chapter. The influence of the substrate’s porosity on the coatings’ crack resistance has been proven. The approach based on the ratio between the crack length upon indentation of the Vickers indenter and the fracture toughness is presented to evaluate the resistance of coatings to cracking. It is demonstrated that as protective decorative coatings on external walls of buildings age, the mechanism of their breakdown shifts from elastic-plastic to brittle, resulting in “embrittlement” of the coatings. It was discovered that “embrittlement” occurs in coatings after a specific period of humidification. Coating peeling after 2 months of humidification is typical of MA-115 coatings, while cracking is typical of PF-266 coatings. The coefficient of intensity of tension decreases as the surface porosity of a substrate is increased to a certain limit.

After a certain period of influence of alternate freezing and thawing on PVAC and polymer-limy coatings on a solution substrate, “embrittlement” develops. After 15-20 testing cycles, cracks in coatings at the cave-in of a Vikkers indentor occur. When examining thermoaging, it was discovered that as the time of thermoaging increases, the value of the coefficient of intensity of tensions increases naturally. Stresses in coatings are calculated.

Author(S) Details

Valentina Ivanovna Loganina
Penza State University of Architecture and Construction, Penza, Russia.

Ludmila Viktorovna Makarova
Penza State University of Architecture and Construction, Penza, Russia.

Roman Viktorovich Tarasov
Penza State University of Architecture and Construction, Penza, Russia.

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