Evaluation of polymer dispersion biocides

Prior to adoption, polymer dispersion biocides must be tested in the products they are intended to preserve under conditions as close as possible to those that will be experienced in use. 

One of the difficulties inherent in the evaluation of these products is the changing nature of polymer dispersions after manufacture. Often the reaction between added redox chemicals and residual monomer will continue for some time after the dispersion has been produced. 

Therefore, in laboratory testing, it is extremely important that the addition of biocide to the polymer dispersion copies as far as possible the conditions that would occur at the production plant. In almost every case a polymer dispersion sample that has been stored prior to addition of biocide will show less degradation of the bioeide than if the bioeide was added when the polymer dispersion was freshly made. This requires all additions of biocide samples to unprotected polymer dispersions to be made at the polymer dispersion plant or laboratory where the polymer dispersion is produced. As a consequence the additions must be made while the polymer dispersion is at the same temperature, pH and redox state that would occur during biocide addition to a production batch. 

A number of methods are available for evaluating the microbial resistance of polymer dispersions and biocides added to them but there are, as yet, no recognised international standards. Nevertheless, the work of the International Biodeterioration Research Group (IBRG) in this field has lead to the production of a draft method (IBRG, 2001), which, it is believed, can be used as an efficacy test for biocides within the scope of the European Biocidal Products Directive and for predicting the in-use performance of polymer dispersion biocides. 

Other organisms known to be appropriate to the specific product under test may be used in addition to or in place of those listed above. 

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