Study on needle-punched nonwoven fabrics made from shrinkable and non-shrinkable acrylic blends. Part III: filtration characteristics

This paper reports the filtration behaviours of needle-punched bulked nonwoven fabrics made from shrinkable and non-shrinkable acrylic blends. The basic idea of the present work is to explore the possibility of structural changes in needle-punched nonwoven fabrics made from blends of shrinkable and non-shrinkable acrylic fibres, as in the case of an acrylic bulked yarn, to improve the filtration behaviour. In Part I and Part II of this series, compressional and transmission characteristics of these fabrics were reported, respectively. The effects of variables, namely fabric areal density, needle punch density and the proportion of shrinkable acrylic fibre in the blend, on various filtration-related properties of needle-punched nonwoven fabrics have been studied by relaxing the shrinkable component of the fabric using hot steam treatment. A three-variable factorial design technique proposed by Box and Behnken was used to investigate the combined interaction effect of the above variables on the filtration properties of these fabrics. The fabric areal density and needle punch density were found to have a significant effect on filtration efficiency as well as pressure drop. The proportion of shrinkable acrylic fibre has little effect on filtration efficiency, but the trends are dependent on the needle punch density.