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The utilisation of ultrasonics has been shown to enable efficient and environmentally friendly textile wet processing. This study conducted a comparative investigation of silk degumming by using a conventional heating bath and ultrasonic irradiation at a range of ultrasonic frequencies. Citric acid, sodium carbonate and papain were used as degumming agents. Sericin degumming rate, fibre whiteness, fibre surface morphology, fibre structure characteristics and fibre tensile properties were measured and analysed. Results showed that ultrasonics at a lower frequency produced a greater degumming rate than at a higher frequency. Ultrasonics is a more effective way than the conventional heating bath of improving degumming efficiency, especially at a lowered temperature of 60°C. When sodium carbonate was applied at 90°C, a conventional heating bath was found to be more effective than ultrasonics. Papain was found to be more effective in sericin removal than citric acid and sodium carbonate, with a degumming rate of 22% achieved at 60°C under ultrasonic irradiation at 40 kHz. The use of papain can, however, cause a possible overreaction to silk under certain severe conditions, resulting in a loss of fibre whiteness. Negligible changes in fibre structure characteristics were measured by Fourier Transform-infrared spectroscopy and X-ray diffraction after ultrasonic degumming with papain. Slightly reduced fibre strength and increased fibre extensibility were observed in ultrasonically degummed silk samples compared with un-degummed and conventionally degummed silk samples.

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Ultrasonic technology has shown the potential to reduce the cost and environmental impact of textile wet processing. This work investigates the effects of ultrasonic irradiation as a pretreatment on wool and its application in low-temperature dyeing. A significant increase in dye uptake and color strength was observed on the fabric ultrasonically pretreated at 40 kHz, followed by that at 80 kHz and the conventionally treated sample, in both acid dyeing and reactive dyeing. This could be due to the changes of the fiber surface structure and modification of the chemical structure in the cell membrane complex as a result of ultrasonic pretreatment. In acid dyeing, a 20% increase in dye uptake was achieved at 70℃ upon applying ultrasonic pretreatment at 40 kHz. With the assistance of a leveling agent, 80% dye uptake of the fabric treated with ultrasonics at 40 kHz was measured at 70℃ in reactive dyeing. Ultrasonic pretreatment can be applied in raw wool scouring and fabric scouring to achieve an efficient dye uptake, and these are also discussed in this paper.

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