Physicochemical Limitations of Capillary Models Applied to High-Concentration Polymer Solutions

Area of Science:

• Additive Manufacturing
• Materials Science
• Fluid Dynamics

Background:

• Binder jet printing (BJP) advancements necessitate novel binder-powder systems for enhanced material compatibility and part strength.
• Current binder absorption models in BJP primarily focus on powder property variations, overlooking fluid dynamics.
• Understanding binder absorption is crucial for developing new binders and improving printing performance.

Purpose of the Study:

• To investigate the influence of polymeric binder fluid properties on absorption dynamics in binder jet printing.
• To evaluate the accuracy of capillary models in predicting binder absorption time, considering fluid properties.
• To explore the impact of polymer-specific characteristics like molecular weight and entanglement on binder absorption.

Main Methods:

• Utilized a design-of-experiments approach to systematically vary fluid properties.
• Employed an optical observation method to track the absorption time of binder droplets.
• Analyzed the correlation between fluid properties, polymer characteristics, and absorption dynamics against capillary model predictions.

Main Results:

• Capillary models accurately predict absorption time for dilute binder solutions.
• Model predictions deviate significantly for highly concentrated binder solutions.
• Polymer entanglement emerges as a dominant factor in concentrated solutions, drastically reducing absorption rates.
• Increased evaporation due to powder bed heating can exacerbate polymer entanglement effects.

Conclusions:

• Existing capillary models are insufficient for predicting binder absorption in concentrated polymeric solutions used in binder jet printing.
• Polymer entanglement significantly impacts binder absorption dynamics, leading to slower absorption than predicted by current models.
• Future binder jet printing models must incorporate polymer entanglement to accurately simulate binder behavior and facilitate the development of advanced binders.