Hygienic assessment of polymeric coatings by physico-chemical and microbiological approaches

Abstract Various coatings currently used in wall panels for building applications were assessed. The hygienic properties of coatings were investigated by the ease of cleaning as well as in terms of their anti-fouling property. The surface energy of the coatings was calculated using the acid- base approach (according to van Oss, Chaudhury and Good). In our work, the results are found to be relatively consistent and we discriminated apolar, monopolar basic, or coatings with acid-base character. As far as the fouling aspect is concerned, the bacterial survival, expressed as percentage, is governed by environmental factors such as relative humidity and the presence of nutrients on coatings. In our experimental conditions, the surface properties of the coatings have been found to play a secondary role. On clean coatings, the percentage of survival increases with a decrease of the relative humidity. After 24 h of exposure to a wet environment, the survival is around 11-15% on poly(ethylene terephthalate) (PET) and poly(vinylidene fluoride) (PVDF) coatings with an acid-base character and an acidic parameter (γS + ≥ 0.1 mJ/m2). The percentage of survival is twice as high as on monopolar basic coatings in the same environmental conditions. Nevertheless, it is 100% in a dry environment. On the other hand, on soiled coatings, the nutrients play a protective role in the bacterial survival as the percentage of survival is 100% in a wet environment and 60-78% in a dry environment. Regarding the ease of cleaning, the cleaning kinetics is ten times as fast on surfaces with an acid-base character as on highly monopolar basic coatings (with the basic parameter, γS -higher than 8 mJ/m2). As a rule, the more the acid-base character of the coating surface, the easier it was to clean in our experimental conditions. This last point underscores the importance of controlling the coating cleaning and the necessity for proposing easy-to-clean materials in order to ensure hygiene. Keywords: Polymeric coatingsteelfoulingcleaningbacteria.