2. ULTRASOUND
• The possibility of dyeing textile using
ultrasound was started in 1941
• Ultrasound is an
oscillating sound pressure wave with
a frequency greater than the upper
limit of the human hearing range
• ultrasonic frequencies lie between 20
kHz and 500 MHz
3. BUBBLING
PHENOMENON
•Ultrasound energy is sound waves with
frequencies above 20,000 oscillations
per second.
•In liquid, these high-frequency waves
cause the formation of microscopic
bubbles, or cavitations.
•They also cause insignificant heating
of the liquid. Ultrasound causes
cavitational bubbles to form in liquid.
4. •When the bubbles collapse,
they generate tiny but powerful
shock waves
•There is a compression or
rarefaction during each cycle
of wave.
•When ultrasonic waves are
absorbed in liquid system,the
phenomenon of cavitations
takes place, which is the
alternate wave formation,
oscillation and collapse of tiny
bubbles or cavities.
5. •During the rarefaction of
the portion of the wave cycle,
dissolved gas molecules act
as nuclei for the formation of
cavities, which may expand
relatively slowly up to a diameter
as much as 0.1 cm. and then
quickly collapse during the
compression portion of the cycle
6. GENERATION OF
ULTRASONIC
WAVES
•The ultrasonic waves can be
generated by a variety of ways.
Most generally known are the
different configurations of whistles,
hooters and sirens as well as piezo-
electric and magnatostrictive
transducers..
7. •The working mechanism of sirens
and whistles allows an optimal
transfer of the ultrasonic sound to
the ambient air
•In the case of magnatostrictive
and or piezo-electric transducers
of ultrasonic waves, the
generators as such will only
produce low oscillation
amplitudes, which are difficult to
transfer to gases.
8. •The occurrence of cavities
depends upon several factors
such as the frequency and
intensity of waves,
temperature and vapour
pressure of liquids.
9. EQUIPMENTS
FOR
ULTRASONICS
• Generator and converter or cleaning
bath are the two main components
of ultrasound equipment.
• Generator converts 50 to 60 Hz
alternate current to electrical energy
of high frequency.
10. •This electrical energy is fed to
the transducer where it is
transformed to mechanical
vibration.
•The transducer system vibrates
longitudinally transmitting
waves into liquid medium. As
these waves propagate
cavitation occurs.
11. •Prototype dyeing machine was
designed for continuous dyeing
of yarn and fabric.
•The system mainly consists of
the ultrasonic tank, transport
system and microprocessor,
which is used to monitor the
process.
•Ultrasonic tank is of 92 x 60 cm
dimensions and capacity up to
200 litres. Temperature can be
varied up to 100°C by
thermostatic control.
12. DYEING
•The use of ultrasound in the dyeing
of textile can be explained as:
when ultrasound waves are
absorbed in the liquid system the
phenomenon of cavitations takes
place. Cavitations can liberate
entrapped gases from liquid or
porous materials like textiles,
dyebath etc. The influence
of ultrasound on dyeing is
explained tohave three-way
effects:
13. •The influence of ultrasound on
dyeing is explained tohave
three-way effects:
• (I) Dispersion: Breaking up of
micelles and high molecular
weight aggregatesin to uniform
dispersion in the dye bath.
• (ll) Degassing: Expulsion (
dissolved or entrapped gases or
air moleculesfrom fiber
capillaries and
14. interstices at the cross over points
of fiber in toliquid and removed
cavitations.
• (Ill) Diffusion: Accelerating the
rate of diffusion of dye inside the
fiber by piercing the insulating
layer covering
the fiber and accelerating the
interaction between dye
and fiber.
15. ADVANTAGES• Energy savings,
• Process enhancement
• Reduced processing times,
• Maintains or improves product quality
• Reduces the use of auxiliary
chemicals.
• Ultrasound is more beneficial to the
application of water insoluble dyes to
the hydrophobic fibres
• Low temperature processes
• Lesser load to the effluent
