A Novel In-Line Measurement and Analysis Method of Bubble Growth-Dependent Strain and Deformation Rates during...

Area of Science:

• Polymer Science and Engineering
• Materials Science
• Rheology

Background:

• Bubble growth in polymer melts is significantly affected by elongational viscosity.
• Accurate prediction of bubble growth requires understanding initial expansion and deformation behavior.
• Key influencing factors include polymer type, blowing agent concentration, and processing conditions.

Purpose of the Study:

• To present a novel in-line observation and analysis method for initial bubble expansion and deformation.
• To enable real-time analysis of foaming processes within bead foam extrusion.
• To investigate the influence of polymer type and processing conditions on bubble behavior.

Main Methods:

• Developed an in-line observation system using a borescope and camera integrated into an underwater pelletizer's water box.
• Utilized nitrogen as a blowing agent injected into polystyrene (PS) and polylactic acid (PLA) melts.
• Implemented a camera trigger system based on angular step signal analysis of the pelletizer's rotary encoder for precise image capture.

Main Results:

• The developed in-line method provides reliable data on initial bubble expansion and deformation.
• Differences in bubble growth behavior were successfully analyzed in-line.
• The analysis demonstrated dependency on real foaming process conditions and polymer type (PS vs. PLA).

Conclusions:

• The novel in-line observation method is effective for analyzing initial bubble growth dynamics.
• This technique facilitates a deeper understanding of polymer foaming processes.
• It supports the development of advanced polymers for foaming applications by providing critical rheological insights.