Polyacrylate-water partitioning of biocidal compounds: Enhancing the understanding of biocide partitioning between render and water

In recent years, the application of polymer-based renders and paints for façade coatings of buildings has risen enormously due to the increased mounting of thermal insulation systems. These materials are commonly equipped with biocides - algaecides, fungicides, and bactericides - to protect the materials from biological deterioration. However, the biocides need to be present in the water phase in order to be active and, hence, they are flushed of the material by rain water. In order to increase the knowledge about the partitioning of biocides from render into the water phase, partition constants between the polymer - in this case polyacrylate - and water were studied using glass fibre filters coated with polyacrylate. The polyacrylate-water partition constants (log. K_AcW) of ten biocides used in construction material varied between 1.66 (isoproturon) and 3.57 (dichloro- N-octylisothiazolinone). The correlation of the polyacrylate-water partition constants with the octanol-water partition constants is significant, but the polyacrylate-water partition constants were predominantly below octanol-water partition constants (K_ow). The comparison with render-water distribution constants showed that estimating the leaching of biocides from render based on polymer-water partitioning is a useful and practical tool.