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An automated method and device for the measurement of coating flexibility

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Abstract

A new method for determining the flexibility of paints and other coatings has been developed. Coated aluminium strips are stretched and the damage caused to the coating during stretching is monitored by means of an automatic image processing system. The stretching device, with a lighting and camera system specially designed to withstand cold conditions down to −25°C, gives useful information about the performance of coatings in cold climates. In addition to the elongation at which the paint film starts to crack, the development of cracking is also measured. A reduction in the test temperature was found to impair the flexibility properties of paints. Ageing can either impair or improve the flexibility properties of paints. The effect depends on the pain and the weathering time.

Rusume

On a mis au point une nouvelle méthode automatisée de détermination de la flexibilité de peintures et autres revêtements. Des bandes d'aluminium couvertes d'un revêtement sont étirées dans le dispositif et la détérioraton du revêtement est contrôlée au cours de l'allongement par un système de traitement d'images automatisé. On mesure l'allongement à partir duquel le film de peinture commence à se fissurer, ainsi que la progression de la fissure. Le dispositif d'étirement, l'éclairage et le système caméra, spécialement conçus pour supporter des conditions de froid allant jusqu'à −25°C, donnent des renseignements utiles sur la performance des revêtements sous climats froids.

Le méthode d'analyse par image permet à la fois de détecter et d'analyser les fissures sur les surfaces. Les algorithmes d'inspection sont basés sur un pré-traitement morphologique et une identification statistique des fissures.

On s'est aperçu qu'une réduction de la température d'essai diminuait les propriétés d'extensibilité des peintures. Un vieillissement accéléré peut soit améliorer soit affaiblir les propriétés de flexibilité des peintures. L'effet dépend de la peinture et du temps d'exposition. Le taux de fissuration augmente aussi, en général, quand diminue l'allongement auquel se produit la première fissure.

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Authors and Affiliations

  1. Technical Research Centre of Finland, Forest Products Laboratory, PO. Box 207, SF-02151, Espoo, Finland

    T. Lappalainen, T. Kanko & P. Ahola

  2. Department of Applied Physics, University of Kuopio, PO Box 1627, SF-70211, Kuopio, Finland

    H. Olkkonen

Authors
  1. T. Lappalainen
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  2. T. Kanko
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  3. H. Olkkonen
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  4. P. Ahola
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Lappalainen, T., Kanko, T., Olkkonen, H. et al. An automated method and device for the measurement of coating flexibility. Materials and Structures 26, 614–620 (1993). https://doi.org/10.1007/BF02472836

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  • DOI: https://doi.org/10.1007/BF02472836

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