Additive-Free and Support-Free 3D Printing of Thermosetting Polymers with Isotropic Mechanical Properties

Area of Science:

• Materials Science and Engineering
• Polymer Chemistry
• Additive Manufacturing

Background:

• Thermoplastic 3D printing is accessible due to easy melting and shaping.
• Thermosetting polymers pose challenges for 3D printing due to their inability to be reshaped after cross-linking and the need for specialized resins or high filler content.
• Existing methods for 3D printing thermosets involve photopolymerization or extrusion with significant rheology modifiers.

Purpose of the Study:

• To develop a novel 3D printing process for pure, unmodified commercial epoxy polymers.
• To overcome the limitations of current thermoset 3D printing techniques.
• To achieve high-resolution, isotropic mechanical properties in 3D printed thermoset parts.

Main Methods:

• A rheology-modifier- and photoinitiator-free 3D printing process was developed for a commercial epoxy polymer.
• A low-cost, non-Newtonian support material that transitions between solid and fluid states under shear stress was utilized.
• The process enables 'one-step' curing after printing complex 3D structures.

Main Results:

• The developed In-Bath Print and Cure (IBPC) process successfully 3D printed pure epoxy without modification.
• One-step curing eliminated interlayer adhesion issues, leading to unprecedented isotropic mechanical properties.
• The process demonstrated high speed (over 720 cm/min) and high resolution (down to 220 μm filament size).

Conclusions:

• The IBPC process offers a low-cost, scalable, and high-performance solution for 3D printing thermosetting polymers.
• This method significantly advances the capabilities for creating complex thermoset structures with excellent mechanical integrity.
• Potential applications span hobbyists, aerospace components, and fiber-reinforced composites.