Design and production of antibacterial breathable membranes

The aim of this study is to design and produce of breathable membranes providing antibacterial property. Recently, the use of membranes which prevent the passage of liquids containing microorganisms and allow passage of water vapor, has been greatly increased in protective textiles and medical products. Antibacterial properties are also of great importance to prevent migration of pathogens by air or contact from fluids containing microorganisms that they will keep on the surface of these membranes. This property can be achieved permanently by attaching the Quaternary Ammonium Salt (QAS) diol, which is used as an antibacterial agent, to the polymer main chains. Breathable membranes are generally produced in microporous or nonmicroporous hydrophilic form. In microporous membranes, there are large pores that only water vapor molecules can pass through, whereas in hydrophilic membranes, water vapor molecules diffuse through the polymer chains especially through amorphous regions. The most important property of hydrophilic membranes is that they have polymeric backbones containing hydroxyl, ether, amide, or urethane groups which can make hydrogen bridges with water vapor molecules. The antibacterial agents should not reduce the ability of the system to make a hydrogen bridge, and should not easily leach out with the effect of liquids from the structure. To provide these properties polyurethane as a polymer and QAS as an antibacterial agent are suitable. In this study, nine different polyurethane containing QAS diol and isocyanate with different ratios were synthesized successfully by using solution polymerization method. Amorphous membranes with ~32 μm thickness were produced from synthesized polyurethanes and their thermal, mechanical, morphological properties and antibacterial activities were determined. The effect of changes in thermal and morphological properties on vapor permeability has been investigated. It has been determined from the DSC and DMA thermographs that an increase in the amount of QAS does not cause any significant alteration in the glass transition temperature, but an increase in the amount of isocyanate causes an increment in glass transition temperature approximately 5 °C. While there was no significant effect of QAS on mechanical properties, increment of isocyanate amount was reduced the molecular flexibility and so increased hardness. Water permeability was increased with increasing cationic QAS adding to the structure, reduced with the increment isocyanate amount. Finally, antibacterial activity of membranes were determined, unmodified membranes were not show antibacterial activity against Staphylococcus aureus and Escherichia coli, it was determined that as the amount of QAS increases in the membrane structure the antibacterial activity increases. It has also been found that the modified membranes can inactivate S. aureus bacteria at a higher rate than E. coli bacteria.