Photo-Curable Polyimide Resin for Low-Shrinkage 3D Printing
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Solution Overview
Problem
Existing 3D printing methods for polyimides face challenges such as low throughput, limited resolution, surface roughness, anisotropic mechanical properties, and internalized micro-defects due to solvent-based printing and high-temperature annealing, leading to carbon residues and shrinkage.
Innovation Solution
A method involving the use of high-viscosity polyamic acid oligomer formulations in a photo-reactive monomer solution, forming an interpenetrating polymer network (IPN) followed by low-temperature thermal conversion to polyimide, eliminating non-reactive solvents and minimizing shrinkage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If FDM extrusion technology is used to print polyimides, then the material can be printed as a thermoplastic polymer, but the throughput is low, resolution is limited, surface roughness increases, and anisotropic mechanical properties occur
Solution Approach 1:
The patent replaces the mechanical extrusion system (FDM) with a photochemical system (VPP). Instead of melting and extruding thermoplastic polyimide through a nozzle, the invention uses photopolymerization of a liquid resin containing PAA precursor and photo-initiator to form a crosslinked polyimide network directly in the desired shape, eliminating mechanical extrusion limitations
Solution Approach 2:
The patent changes the physical state of the printing material from solid thermoplastic filament to liquid photopolymerizable resin. The resin contains PAA precursor (10-50 wt%), photo-initiator (1-10 wt%), and reactive monomer (50-85 wt%), which can be cured at lower temperatures compared to traditional polyimide processing, enabling VPP manufacturing
2Ease of manufacture
If FDM extrusion technology is used to print polyimides, then the material can be printed as a thermoplastic polymer, but the manufacturing precision and surface fidelity are limited
Solution Approach 1:
The patent replaces mechanical extrusion with optical patterning technologies (LCD, DLP, laser scanning) that can achieve pixel resolution capabilities of 20-50 μm. The photopolymerization process cures the liquid resin layer by layer with high precision, dramatically increasing surface fidelity and eliminating the layering artifacts inherent in FDM
Solution Approach 2:
The invention uses a liquid resin formulation with controlled viscosity (100-2000 cps) that is optimized for VPP processing. The resin contains reactive monomers and PAA precursor in a ratio that enables complete curing without residual solvent, achieving smooth surfaces and high dimensional accuracy
3Quantity of substance
If a high concentration of PAA precursor (e.g., 20 wt%) is used in the printing resin, then the polyimide content is increased, but the viscosity becomes too high for VPP printers and solubility challenges arise
Solution Approach 1:
The patent optimizes the resin formulation by using reactive monomers (50-85 wt%) with appropriate functional groups that are compatible with PAA precursor. The combination of specific monomer types, PAA molecular weight (1000-100,000 g/mol), and concentration ratios achieves the optimal balance: 10-50 wt% PAA provides sufficient polyimide content while maintaining viscosity of 100-2000 cps for VPP processing
Solution Approach 2:
The invention creates a composite resin system where PAA precursor (polymer), reactive monomer (small molecule), and photo-initiator (catalyst) work synergistically. The reactive monomer acts as both solvent and crosslinking agent, ensuring the PAA precursor remains soluble during printing and forms a robust network after curing, eliminating solubility issues
4Ease of manufacture
If a large amount of non-reactive solvent is used in the printing resin, then the viscosity is reduced for better printability, but mass loss and shrinkage of approximately 50% occur during annealing
Solution Approach 1:
The patent completely removes non-reactive solvents from the resin formulation. Instead, it uses only reactive monomers (50-85 wt%) that participate in the photopolymerization reaction and become part of the final crosslinked network. This extraction of harmful non-reactive components eliminates the source of mass loss and shrinkage during curing
Solution Approach 2:
The invention converts the potential harm of having any solvent present by using reactive monomers instead of non-reactive solvents. These reactive monomers serve dual purposes: they provide the necessary fluidity for printing (acting as solvent) and simultaneously participate in crosslinking to form the final network structure (acting as structural component), thus converting what would be a source of shrinkage into a beneficial structural element
5Temperature
If a high temperature anneal (400° C.) is used to convert PAA to PI and remove non-reactive components, then the polyimide structure is formed, but carbon residues and ash contents increase, resulting in black coloration
Solution Approach 1:
The patent changes the curing temperature from high temperature (400° C.) to a lower range (60-200° C.) by using photopolymerization instead of thermal conversion. The photo-initiator absorbs UV light and generates radicals or cations that initiate polymerization at ambient or slightly elevated temperatures, eliminating the need for high-temperature annealing that causes carbonization
Solution Approach 2:
The patent replaces thermal energy input (heating to 400° C.) with optical energy input (UV irradiation). The photo-initiator absorbs UV photons and triggers the polymerization reaction, substituting a thermal process that causes decomposition and carbonization with a photochemical process that occurs at lower temperatures and produces no carbon residues
6Ease of manufacture
If non-reactive solvents are used in the printing resin, then the viscosity is reduced for better flow, but the solvents are burned off during annealing causing mass loss and shrinkage
Solution Approach 1:
The patent extracts and removes all non-reactive solvents from the formulation, replacing them entirely with reactive monomers. This eliminates the need for solvent evaporation or burn-off steps, preventing the dimensional changes and defects associated with solvent removal
Solution Approach 2:
The invention converts the role of non-reactive solvents into reactive monomers. These monomers provide the necessary fluidity for printing (beneficial property) while simultaneously participating in the crosslinking reaction to form the final network (structural contribution). This conversion eliminates the harmful effect of solvent loss while maintaining the beneficial effect of low viscosity during printing
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
Achieves high dimensional accuracy and reduced shrinkage, maintaining material strength and transparency, while overcoming the limitations of traditional 3D printing techniques.
Implementation Method 1
a photo-initiator is dispersed into a photo-reactive monomer to form a liquid resin. Electromagnetic radiation is then applied (e.g., in a 3D printing operation) to solidify the liquid resin and to substantially form a PAA-based interpenetrating polymer network (IPN)
Implementation Method 2
the PAA-based IPN is thermally cycled to higher temperatures to convert the PAA-based IPN into a polyimide-based IPN
Data Source
AI summary
A method of making a polyimide (PI)-based material. In one embodiment, the method begins by dispersing a polyamic acid (PAA) oligomer and photo-initiator into a photo-reactive monomer to form a liquid resin. In contrast to the above-described prior art, the liquid resin is substantially devoid of any non-reactive solvents. Electromagnetic radiation is then applied (e.g., in a 3D printing operation) to solidify the liquid resin and to substantially form a interpenetrating polymer network (IPN) in which the PAA oligomer is entangled within the network formed by the photo-reactive monomer but remains substantially independent and un-crosslinked from the PAA oligomer. Thereafter, the PAA-based IPN is thermally cycled to form a polyimide-based IPN.