Dragana Kopitar

Impact of calendering process on nonwoven geotextiles hydraulic properties

The influence of the calendaring process of nonwoven geotextiles on the water permeability normal to their planes, including influence of different loads, as well as pore characteristics investigated by two different methods has been studied. Methods of pore characteristics differ in obtaining different pore parameters. Two groups of samples were produced whereas first group is bonded by needle punching, while second group is needle punched samples taken from first group and additionally bonded by calendaring. Mass per unit area for both groups is in range of 150 to 500 g/m2, with increasing by 50 g/m2 for the next sample within groups. Calendaring process decrease water permeability of geotextile, but also decreases interval of geotextile water permeability change due to the applied pressure. Calendared geotextiles have controlled and predictable compressibility, respectively structure which will not significantly change in the practical application.

Influence of nonwoven fabric pore sizes on water vapor resistance

The influence of nonwoven fabric pores using the Brunauer–Emmet–Teller method, dry sieving and capillary flow porometry on water vapor resistance were investigated. For a better understanding of the nonwoven thickness impact on pores and water vapor resistance (and therefore the influence on comfort), two types of samples were investigated: nonwoven fabric bonded with the needling and nonwoven fabric additionally bonded with the calendering process. Water vapor resistance increased with increasing nonwoven fabric thickness, whereby it ranged from 11.33 to 15.62 m2 Pa W−1 for the non-calendered samples and it ranged from 5.19 to 9.85 m2 Pa W−1 for the calendered ones. Water vapor resistance showed a good linear correlation with the specific surface area, pore volume, apparent opening size and mean flow pore diameter.

Comfort and microbial barrier properties of garments worn next to the skin

Compared with viscose fibre, modal fibre is characterized by some advantageous properties such as higher dry and wet tenacities, higher wet modulus, lower water retention capacity and lower level of swelling. Impact of different knitted fabric structure made of cotton and 97 % CMD/3 % EL fibres on thermo-physiological comfort and microbial barrier properties were investigated. All knitted fabrics have very good physiological properties. The microbial barrier permeability of knitted fabric after extreme contamination with bacterial spores in dry state showed that double jersey offered more effective microbial barrier than the single jersey knitted fabrics respectively the greater thickness of double jersey knitted fabric provide more difficult barrier to bacterial spores to pass. In wet state all knitted fabrics have more effective microbial barrier which could be explained by cellulose fibres swelling. In wet state 97 % CMD/3 % EL single jersey knitted fabric have more effective microbial barrier then cotton double and single jersey knitted fabrics.

Influence of pressure on water permeability and characteristic opening size of nonwoven geotextiles

The samples investigated in this paper are nonwoven geotextiles manufactured by mechanical carding process, bonded by needling process. Part of the samples was additional bonded by thermal calendaring process. Sampling was conducted according to the standard for geotextile with certain modifications. The samples were tested for water permeability perpendicular to the plane of samples, using loads of 2, 20 and 200 kPa. Characteristic opening size of geotextiles was tested using sieving method. Conducted research shows that external force impact, in this paper different loads, significantly change structure and properties i.e. thickness and water permeability of geotextile.