Determination of diffusion coefficients of biocides on their passage through organic resin-based renders

• The diffusion of biocides through organic resin-based renders is described.
• The rate of the leaching is generally determined by the rate of transport of biocide in the water-filled pores.
• The organic modifier in the render influences the diffusion driven transport of biocides.

In this study the diffusion coefficients of isoproturon, diuron and cybutryn in acrylate and silicone resin-based renders were determined. The diffusion coefficients were determined using measuring concentrations of biocides in the liquid phase after being in contact with renders for specific time intervals. The mathematical solution of the transient diffusion equation for an infinite plate contacted on one side with a limited volume of water was used to calculate the diffusion coefficient.The diffusion coefficients through the acrylate render were 8.10·10−9 m2 s−1 for isoproturon, 1.96·10−9 m2 s−1 for diuron and 1.53·10−9 m2 s−1 for cybutryn. The results for the silicone render were lower by one order of magnitude. The compounds with a high diffusion coefficient for one polymer had likewise high values for the other polymer.