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Direct Ink Writing and Photocrosslinking of Hydroxypropyl Cellulose into Stable 3D Parts Using Methacrylation and
Mehmet-Talha Yapa1,2, Gopakumar Sivasankarapillai1,2, Jacques Lalevée3,4
1Chair of Forest Biomaterials, Institute of Earth and Environmental Sciences, Faculty of Environment and Natural Resources, University of Freiburg, Werthmanstr. 6, 79085 Freiburg im Breisgau, Germany.
Polymers
|February 13, 2025
Summary
Methacrylated hydroxypropyl cellulose (MAHPC) inks show improved rheology for 3D printing but have a narrow UV-cure window. Blending MAHPC with hydroxypropyl cellulose (HPC) enables stable, high-fidelity 150-layered parts via UV-assisted direct ink writing.
Area of Science:
- Materials Science
- Polymer Chemistry
- Biomaterials
Background:
- Hydroxypropyl cellulose (HPC) is a promising biomaterial for 3D printing.
- Modifying HPC with photocrosslinkable groups can enhance its printability and performance.
- Understanding the relationship between chemical structure and rheological properties is crucial for direct ink writing (DIW).
Purpose of the Study:
- To evaluate the rheological properties, photocrosslinking kinetics, and printability of methacrylated hydroxypropyl cellulose (MAHPC) inks for DIW.
- To investigate the effect of methacrylate substitution degree on ink performance.
- To determine the feasibility of producing multilayered 3D parts using UV-assisted DIW with MAHPC and HPC blends.
Main Methods:
- Preparation and characterization of MAHPC with varying substitution degrees (L_MAHPC and H_MAHPC).
- Rheological measurements (dynamic moduli, shear thinning, shear recovery) under varying strain and time.
- UV-rheology to study photocrosslinking kinetics using the Sestak-Berggren model.
- Direct ink writing (DIW) experiments to assess printability and multilayer part fabrication.
Main Results:
- MAHPC inks exhibited superior rheological properties for DIW compared to unmodified HPC, including enhanced shear dynamic moduli, shear thinning, and recovery.
- Both L_MAHPC and H_MAHPC inks achieved complete photocuring within 30 seconds under UV light.
- A narrow UV-cure time window for neat MAHPC inks led to part fracture with prolonged UV exposure, precluding multilayer printing.
- Blending MAHPC with HPC created an optimal balance, enabling the successful fabrication of stable, high-fidelity 150-layered parts.
Conclusions:
- Methacrylate grafting significantly improves the rheological suitability of cellulose derivatives for DIW.
- The photocrosslinking kinetics of MAHPC inks follow an autocatalytic model, but a narrow cure window limits neat ink applications for multilayer structures.
- Designing photocrosslinkable cellulose derivatives with controlled substitution is essential for achieving high fidelity and stable 3D printed parts using UV-assisted DIW.
