78 effect of nanochitosan on absorbency figure 17

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7.8 Effect of Nanochitosan on Absorbency Figure 17 depicts the absorbency determined by drop penetration method pertain- ing to nanochitosan-treated cotton fabric. The results show that the absorbency is decreased with the reduction in particle size. This may be elucidated by the example of lotus leaf effect. Distribution of nanochitosan particles as a thin layer over and beneath the surface, (Fig. 16 d f), may roll out the water droplets. The absorbency of nanochitosan-treated fabrics continues to fall within the tolerable limits of conventional wet processing conditions (Chattopadhyay and Inamdar 2013 ). 7.9 Dyeing Behaviour of Nanochitosan-Treated Cotton Fabric As the chitosan structure is very much similar to cellulose, its treatment to cotton is expected to in fl uence the dyeing. Thus, the in fl uence of pretreatment of nanochi- tosan on direct dyeing of cotton has been investigated. The in fl uences of chitosan and nanochitosan pretreatment on dye uptake have been determined. Due to the decrease in the particle of chitosan, the dye uptake by treated cotton fabric, in conventional process, is increased progressively. The results are superior to Fig. 17 In fl uence of particle size on treated cotton fabric absorbency (Chattopadhyay and Inamdar 2013 ) 22 N. Gokarneshan et al.
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corresponding parent chitosan-treated materials. The dye uptake of CHTN-treated samples is found to be signi fi cantly increased, resulting in almost complete exhaustion of dye bath, when acidi fi cation was followed (Chattopadhyay and Inamdar 2013 ). The increased dye uptake due to chitosan treatment may be attributed to the presence of primary amino groups of chitosan. These cations dissipate the negative surface charge on cotton and drives dye molecules to the fi bre. Further, the dye uptake may also been enhanced due to the dyeability of chitosan itself with direct dyes. The nanochitosan due to increased surface area and hence higher accessibility for dye sites put much added value. The primary amino groups on chitosan get protonated (quaternized) in acidic medium having enhanced positive charge, thus forming salt linkages with anionic (sulphonate) groups of residual dye in the bath. Secondly, the higher dye uptake value after acidi fi cation proves the presence of chitosan. The wash fastness and rub fastness properties of direct dyed fabrics were also analysed. As the particle size is reduced, the fastness to washing is improved, which could be considered as the formation of chitosan dye complex in situ. The rubbing fastness is also improved to a certain degree with the particle size decrease. 7.10 In fl uence of Nanochitosan on Crease Recovery The aesthetic appeal of garment/fabric gets downgraded due to susceptibility to creasing. In the conventional method, the problem is overcome by treatment of cotton fabric with different cross-linking agents based on aminoplast resins, e.g.
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  • Fall '19
  • N. Gokarneshan

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