Enhanced, Seamless Ultrasound Introduction Unit for Thermoplastic Melt Treatment

Ultrasonic power stimulation of polymers has been employed to modify their properties for various industrial applications. It is used to disperse particles in polymers or to impregnate continuous fiber-reinforced filaments. These processes operate under extreme conditions, involving temperatures exceeding 400 °C and pressures reaching up to 60 bars. Traditional sound introduction systems rely on moving horns within cavities, which pose significant challenges in maintaining clean environments. The moving horn makes it inconceivable to seal such sound introduction systems. To address these limitations, an innovative tool that incorporates only sealed components capable of introducing sound energy without employing cavities was developed. This technology focuses on optimizing eigenfrequencies to efficiently transfer motion into the polymer channel while minimizing disturbing vibrations and sealing issues. The simulation results reveal the mode of operation between the fourth and fifth resonance of the tool. The measurements of the tool validate this theory, indicating a range of operation between 18.5 kHz and 19.5 kHz. With an amplitude of 15 μm, resulting in a minimum power introduction of 224.03 W/cm² in PLA, the average flow rate gain is 13.6%. This new design reduces the risk of blockages and damage in the processed goods and minimizes the force required to process the polymer.