Abstract:

Objective This study fabricates functional textiles from biological sources using waste plant resources, and the dye was extracted from waste oak leaves. Tussah silk was dyed with oak leaf extract for making ultraviolet (UV)-resistant ecological textiles, which has a significance for the green and sustainable development of the textile industry. The kinetic mechanism of dyeing tussah silk with oak leaf extract was investigated, the dyeing kinetic curve was measured, the pseudo-first-order and pseudo-second-order kinetic equations were fitted, and the thermodynamic parameters were calculated.

Method This study extracted a natural dye solution from oak leaves (Dandong) with deionized water as the extraction solvent. The dyeing properties of oak leaf extract on tussah silk fabric under different conditions were explored by dip dyeing, and the color fastness and UV resistance were measured. The dyeing kinetics curves of oak leaf extract on tussah silk were drawn (70-90 ℃), and the dyeing kinetics parameters were calculated.

Results The influence of dyeing parameters on the dyeing properties of tussah silk fabrics dyed with oak leaf extract was discussed. When the dyeing temperature increased, the K/S values of dyed tussah silk were increased, the L ^*value decreased, and the a^*and b^* values increased, with 98 ℃ identified as optimal dyeing temperature (Tab.1). When the pH were changed from 3.0 to 7.0, the K/S values of the dyed samples were gradually decreased, the L^* value progressively increased, and a^*and b^* values decreased (Tab.2). The K/S values of the dyed samples were increased with the time, and the appropriate dyeing time was found to be 60 min (Tab.3). Moreover, the building-up property of oak leaf extract displayed that K/S values of the dyed tussah silk gradually increased with the dye dosage increasing, and the K/S values tended to increase slowly when the dye dosage was 6.25% (o.w.f)(Fig.3). The results demonstrated that the pseudo-first-order kinetic model was unsuitable for describing the adsorption process (Fig.6 and Tab.1). The pseudo-second-order kinetic fitting curves and parameters calculation results (Fig.7 and Tab.5) exhibited R²>0.99 which was higher than those of the pseudo-first-order kinetic models. Therefore, the adsorption process of oak leaf extract on tussah silk could be accurately described by the pseudo-second-order kinetic equation. The color fastness of tussah silk fabric dyed with oak leaf extract revealed that all the measured color fastness were rated above 3 (Tab.6). In addition, the UV resistance property of tussah silk fabric suggested that the UV transmittance of dyed samples was significantly lower than the undyed sample (Fig.8). The UV protection coefficient (UPF) value of dyed tussah silk fabric reached more than 40 when the dye dosage was more than 7.5% (o.w.f).

Conclusion 1) The optimal dyeing conditions for oak leaf extract on tussah silk were as follows: pH value was 3.0, and dyeing at 98 ℃ for 60 min. The oak leaf extract exhibited good building-up property on tussah silk and could obtain deep color without medium treatment. The color fastness to washing, rubbing and the light was rated above 3.2) The adsorption kinetics study illustrated that the adsorption mechanism of oak extract on tussah silk was consistent with the pseudo-second-order kinetic model. Dyeing rate constant and equilibrium adsorption capacity were increased with temperatures and the half-dyeing time decreased.3) Compared with undyed tussah silk, the UV transmittance of dyed tussah silk was decreased prominently, the UPF value was increased, and the dyed samples had good UV protection performance. When the dye dosage was higher than 7.5% (o.w.f), the UPF value of tussah silk could reach above 40.

Key words: oak leaf dye, tussah silk, ecological dyeing, adsorption kinetics, naturol dye, ultraviolet resistance performance