dc.description.abstract | In this investigation, the influence of alkali treatment on the chemical composition (content of
hemicelluloses), sorption properties and surface charge of jute woven fabrics were studied. In order to
partially remove hemicelluloses, jute fabric was alkali modified with NaOH solutions of different
concentrations (5%, 10% and 17.5%) during 5 min at room temperature. With increasing the NaOH
concentration, the content of hemicelluloses decreased. Untreated jute fabric has 21.76%
hemicelluloses, while after alkali treatments, the content of hemicelluloses decreased down to
13.76%.The content of hemicelluloses has impact on various sorption properties, which can be
evaluated by determination of moisture sorption and water retention value. Moisture sorption values
provide information on the extent of areas accessible to water vapor within the fiber, while water
retention value represented the total water holding capacity of fibers (i.e. all water absorbing and
holding surfaces, cracks and cavities in jute fibers structures). Higher availability of hydroxyl groups
which occurs as a result of removal of hemicelluloses, contributes to higher moisture sorption of
alkali treated jute woven fabrics in relation to untreated. The moisture sorption of alkali treated jute
fabrics increased for 17.3-21.6% in comparison with untreated fabric. Removal of hemicelluloses
causes increase in water retention values. This is a consequence of structure changes (changes in the
size and number of pores and microcracks in fibers) and effective removal of hydrophobic layer on
the fabric surface (fats and waxes), which should enable better hydrophilicity. Alkali treatments
during only 5 min can improve the water retention value up to 49%.
The changes of the fabric surface chemistry caused by removal of hemicelluloses also have
influence on the electrokinetic properties, i.e. surface charge. Zeta potential measurements in a wide
pH range were used for studying the surface charge of textile fabrics, including presence, availability
and nature of surface groups. Untreated jute woven fabric has negative zeta potential in a wide range
of pH due to the presence of hydroxyl and carboxyl groups on the surface subjected to dissociation in
a high pH range. The greater accessibility of dissociated surface functional groups increases the ζpotential. Alkali treated jute fabrics display a positive ζplateau-value (zeta potential value in a basic
range of pH) as a result of removal of fats, waxes and pectin from the fibers surfaces. Also, the
effectiveness of such an alkali treatment process in order to increase the accessibility of surface
groups can clearly be seen from the drastic change of the ζ-potential at low pH values as compared to
untreated fabric. With increasing the concentration of NaOH from 5 to 17.5%, ζ-potential values
decreased. Furthermore, isoelectric point (IEP, a pH value were ζ value is 0) as an indicator of the
nature of functional groups of alkali treated jute fabrics are shifted toward higher pH. This indicates
that after alkali treatment, contribution of acidic groups on the fiber surface become lower. | sr |