Visualization of sonication in high-viscosity polymer melts.

Area of Science:

• Materials Science
• Polymer Engineering
• Acoustics

Background:

• Nanoparticle dispersion in polymer melts is critical for composite materials.
• Conventional extrusion struggles with mixing in high-viscosity polymers.
• Ultrasound effectively disperses nanoparticles in low-viscosity fluids via cavitation and acoustic streaming.

Purpose of the Study:

• To investigate ultrasound-induced flow and acoustic streaming in polydimethylsiloxane (PDMS) melts of varying viscosities.
• To understand the influence of dissolved gases and viscosity on ultrasound-driven fluid dynamics in polymers.
• To identify key parameters for developing ultrasound-assisted polymer processing.

Main Methods:

• Utilized flow visualization techniques.
• Employed Particle Image Velocimetry (PIV) to quantify velocity fields.
• Tested PDMS samples with viscosities of 5, 30, and 300 Pa·s under degassed and non-degassed conditions.

Main Results:

• Non-degassed samples showed significantly enhanced acoustic streaming (up to 20 mm/s) due to dense bubble clouds.
• Degassing reduced velocities (3–6 mm/s) and stabilized flow patterns.
• Very high viscosity (300 Pa·s) drastically reduced velocities, indicating viscosity-dependent attenuation and limited bubble formation.

Conclusions:

• Dissolved gases play a crucial role in amplifying acoustic streaming in viscous polymer melts.
• High melt viscosity and gas content are critical factors influencing ultrasound-induced flow.
• Findings provide insights for optimizing ultrasound-assisted extrusion processes for nanocomposite fabrication.