High Efficiency Particulate Air (HEPA) filters from polyester and polypropylene fibre nonwovens

Abstract

In this work, High Efficiency Particulate Air (HEPA) Filters are designed to keep small harmful particles from entering a control environment or to prevent them from escaping. Nonwoven fabrics for filtration application were produced from polypropylene (PP) and polyester (PET) fibres. The nonwoven spunlaced filters made from these fibres are softer and more flexible compared to traditional glass fibre filters for this application. They also have relatively smaller pores which render high air filtration efficiency. Glass fibres are more harmful to human, compared to polypropylene and polyester fibre which are chemically inert. Hydroentanglement and chemical bonding techniques were utilised in manufacturing nonwovens for dry filtration. Acrylic chemical binder as a foam was applied on wet spunlaced material and subsequently cured in an oven. The crosslinks between the fibres and binder were developed with resulted small pores in the material. Three different waterjet pressures and twodifferent concentrations of chemical binder were applied during the processing. The physical, mechanical and performance properties were evaluated and analysed. Hydroentagling process binds the fibres in a homogeneous way and stabilizes the structure of nonwoven. With the use of finer fibres, the surface area of the filter media shows an increasing number of finer pores. The improved surface of the media and homogeneous cross-section after chemical bonding results in better filtration efficiency.