Biodeterioration of a polyurethane topcoat by Aspergillus niger

Abstract

This study investigates the biodeterioration potential of the polyurethane waterproofing coating PU 636 by Aspergillus niger ERAN01 under in vitro conditions. Two protocols, adapted from the ISO 846 standard, were employed using agar media with different nutrient contents. After 9 weeks of incubation at 27 °C and 80 % relative humidity, macroscopic, microscopic, mechanical, and spectroscopic analyses were conducted to assess biodeterioration. Fungal colonization was more extensive in the presence of glucose, which correlated with visible colour changes (notably yellowing), a statistically significant increase in surface roughness, the formation of surface cavities observed via scanning electron microscopy, and chemical modifications detected through infrared spectroscopy. Signs of hydrolysis of ester and urethane bonds, as well as oxidation of ether linkages were observed. Despite these changes, tensile strength measurements showed no significant degradation of the material's mechanical integrity. The results suggest that A. niger produces hydrolases and metabolites capable of inducing greater physical and chemical deterioration of polyurethane coating in the presence of glucose. This study emphasizes the importance of environmental conditions, particularly nutrient availability, in influencing fungal biodeterioration of polymeric materials and supports the need for adapted methodologies when evaluating the biodeterioration of polyurethane waterproofing coatings.