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Tunable Elasto-Viscoplastic Properties of Polymer Blends for 3D Printing Applications
Ases Akas Mishra1, Manoj Chandregowda2, Janina Faiß3
1Chalmers University of Technology, Department of Industrial and Materials Science, Göteborg, Sweden.
Macromolecular Rapid Communications
|June 23, 2025
Summary
Optimizing elasto-viscoplastic (EVP) fluid properties using dimensionless numbers like Ohnesorge (Oh) and modified Bingham (ξ/Bi) is key for stable 3D printing. Proper formulation minimizes die swelling and enhances shape fidelity in printed structures.
Area of Science:
- Soft Matter Rheology
- Materials Science
- 3D Printing Technology
Background:
- Post-extrusion flow of soft matter is governed by elasto-viscoplastic (EVP) properties, impacting filament stability, die swelling, and shape fidelity in 3D printing.
- Achieving precision in 3D printed structures necessitates optimization of yield stress, viscoelasticity, and extrusion pressure to mitigate excessive die swelling and material spreading.
Purpose of the Study:
- To investigate the influence of EVP rheological properties on the extrusion dynamics of soft matter.
- To systematically assess die swelling, print width, and deposition accuracy in model EVP fluids (Carbopol-polyethylene oxide blends).
- To establish correlations between nanoscale structural features and macroscopic flow behavior, guiding formulation for improved printability.
Main Methods:
- Utilized Carbopol-polyethylene oxide (PEO) blends as model elasto-viscoplastic (EVP) fluids.
- Systematically varied blend composition to analyze die swelling, print width, and deposition accuracy.
- Employed Rheo-Small Angle X-ray Scattering (Rheo-SAXS) measurements to probe nanoscale lengthscales and correlated them with die swelling.
Main Results:
- Die swelling was found to be directly related to characteristic nanoscale lengthscales observed via Rheo-SAXS.
- Parametric analysis using Ohnesorge (Oh) and modified Bingham (ξ/Bi) numbers revealed distinct flow regimes.
- High ξ/Bi (low yield stress) and low Oh (<0.1) resulted in excessive die swelling (up to 1.6x nozzle diameter) and spreading (up to 6x nozzle diameter), leading to drop formation.
- Conversely, high Oh (≥10^2) and low ξ/Bi (≤8x10^4) ensured optimal printability, high shape fidelity, and minimal die swelling.
Conclusions:
- Dimensionless groups, specifically Ohnesorge and modified Bingham numbers, effectively predict and guide the extrusion behavior of EVP fluids.
- Optimal printability and shape fidelity are achieved under conditions of high Oh and low ξ/Bi, characterized by stable filament extrusion.
- Findings provide a framework for EVP fluid formulation and extrusion pressure optimization in 3D printing applications.
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