Cryogenic Extrusion for Pure Thermoset Shape Memory Polymer Printing
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Solution Overview
Problem
Current 3D printing techniques cannot produce pure thermoset polymers, as they require mixing with other polymer systems, leading to reduced shape recovery rates due to irreversible deformation of secondary copolymers, and lack the capability to economically fabricate complex designs with intricate details.
Innovation Solution
A cryogenic sprayer-assisted extrusion 3D printing method that increases the viscosity of shape memory polymer (SMP) epoxies to enable extrudability and immobilize polymeric chains, allowing for the fabrication of pure thermoset SMP epoxies and composites, such as those with graphene nanoplatelets, without physical or chemical cross-linkers, and triggers shape change through thermal or electrical stimuli.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional 3D printing techniques are used with thermoset polymers mixed with other polymer systems, then the polymers can be printed, but the shape recovery rate deteriorates due to irreversible deformation of secondary copolymers
Solution Approach 1:
The invention extracts and removes the secondary copolymers from the polymer system, using only pure thermoset SMP polymers without any physical or chemical cross-linkers. This eliminates the source of irreversible deformation while maintaining printability through the use of liquid precursors that can be extruded and cured in place.
Solution Approach 2:
The invention changes the physical state parameter of the SMP polymer from solid to liquid by using low molecular weight liquid precursors. This parameter change enables the polymer to be extruded through a nozzle like a conventional printing material, while the cross-linking density and molecular weight are optimized to ensure proper shape recovery after curing.
2Reliability
If pure thermoset SMP polymers are used without mixing with other polymers, then shape recovery rate is improved, but the ability to be 3D printed deteriorates
Solution Approach 1:
The invention changes the molecular weight and physical state parameters of the SMP polymer to create a liquid precursor that can be extruded. The low molecular weight liquid precursor maintains the pure thermoset composition for optimal shape recovery, while its liquid state enables printability through standard extrusion 3D printing processes.
Solution Approach 2:
The invention performs preliminary curing of the liquid SMP precursor to increase its viscosity before extrusion. This preliminary action prepares the material for printing by giving it sufficient body to be extruded without dripping, while still maintaining the liquid-like flow properties needed for printing. After printing, the sample is subjected to cryogenic temperatures to immobilize the polymeric chains, and then fully cured to achieve the final shape memory properties.
3Ease of manufacture
If liquid SMP precursors with low viscosity are used, then extrudability is improved, but shape immobilization deteriorates
Solution Approach 1:
The invention applies preliminary curing to the liquid SMP precursor to increase its viscosity to an optimal range for extrusion. This partial curing maintains enough fluidity for extrusion while providing initial structure formation. The cryogenic treatment is then applied to immobilize the chains, and final curing completes the process, achieving both extrudability and shape retention.
Solution Approach 2:
The invention utilizes phase transition by subjecting the printed SMP epoxy to cryogenic temperatures (e.g., -10° C. or less) to immobilize the polymeric chains temporarily. This phase transition allows the material to be extruded in a more fluid state and then locked into the desired shape at low temperature before final curing, achieving both extrudability and shape retention.
4Ease of manufacture
If SMP epoxies are cured at room temperature to increase viscosity, then extrudability is improved, but the ability to retain intricate details deteriorates
Solution Approach 1:
The invention uses cryogenic phase transition to immobilize the polymeric chains rapidly after extrusion, locking in intricate details before any significant viscous flow can occur. This ultra-rapid freezing at temperatures of -10° C. or less preserves the fine geometric features much better than room temperature curing, while still enabling extrusion of the precursor material.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the 3D printing of pure thermoset SMP epoxies with enhanced shape memory effects and superior mechanical properties, facilitating the creation of complex, precision components with accelerated recovery rates and reduced fabrication costs, suitable for various applications including deployable systems and actuation systems.
Implementation Method 1
freeze-spraying the printed SMP epoxy with a freezing agent at a second temperature of 10° C. or less
Implementation Method 2
curing the SMP epoxy at a first temperature (e.g., room temperature or higher) to increase its viscosity to at least 500 centipoise (cP) (e.g., 700 cP or more)
Implementation Method 3
The (fully-cured) SMP-based ink can be triggered to change shape by a thermal trigger
Data Source
AI summary
Shape memory polymer (SMP) epoxies and composites, and methods of manufacturing the same, are provided. A three-dimensional (3D) printing technique can be used to fabricate a pure thermoset SMP epoxy. A cryogenic sprayer assisted extrusion type 3D printing method can be used to print SMP epoxies and composites of an SMP epoxy and a nanomaterial additive, such as graphene nanoplatelets (GNP).