Utilisation of Thermoplastic Polymer Waste for Nanofiber Air Filter Production

Abstract

Thermoplastic polymers serving numerous practical applications are widely used in modern societies. For example, thermoplastic polystyrene is used as packaging and building insulation material, while thermoplastic nylon due to its extreme durability and strength is widely used to manufacture textile articles. However, disposal or recycling of used thermoplastic polymer items is problematic and expensive. Thermoplastic polymer waste can be successfully transformed into nano-fibres by electro-spinning. Electro-spinning is an inexpensive method where nano-fibres are generated by a charged jet of polymeric solution in a high-voltage electric field. When the jet travels in the air the solvent evaporates and charged fibres are collected on a grounded rotating drum. The diameter of nano-fibres ranges from 100 to 2000 nm and depends on the appropriate polymer solvent system, technological parameters, and environmental conditions. Due to low basis weight, large surface area to volume ratio, high pore volume, tight pore size and relatively uniform fibre size, utilised polystyrene waste could be used in nano-fibre air filters. The experimental results show that nano-fibre air filters meet High-Efficiency Particulate Air (HEPA) filtration standard, where filtration efficiency of the most penetrating particles (0.3 μm) is >85 %, and can be used to filter hazardous chemicals, biological and radioactive particles from air streams.