Assessing the air filtration efficacy of compressed and uncompressed polyurethane foams

Abstract

The aim of this work was to assess the change in fungal spore filtration efficacy when conventional polyurethane foams were compressed to different ratios. Ninety PPI polyurethane foam samples of 30- and 50-mm thickness were produced, while different samples of 30-mm thickness were compressed to 5 and 25 mm. Air was drawn through foams in a set-up of manifold ports and spores were trapped onto the membrane filters. Micrographs of the polyurethane foams were also collected. An increase in the thickness of the foams resulted in a higher percentage of filtration efficacy. No observable change in the filtration efficiency of the foam was developed when the foam thickness was increased from 30 up to 50 mm. Compression, by reducing the pore size of the foam, allowed a more sinuous path for the air passing through the foam thus resulting in an increase in its trapping ability. Practical applications Compressed foam filters represent a possible way to control dust and microorganisms which can be dispersed in the air of food storage facilities, thus limiting the risk of product contamination. Such filters may find application, for instance, in postharvest warehouses in order to help producers limit the use of chemical treatments on fruit. Furthermore, a compressed polyurethane foam can be easily uncompressed by heating, so that it can be cleaned from the trapped material and compressed once again to be re-used. This could be of great advantage to cut down the production costs wherever air filters are used and need often to be replaced.