Sequential-Cure IPN Resins for Accurate Tough 3D Printing

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Solution Overview

Problem

Conventional vat photopolymerization (VPP) resins used in 3D printing exhibit mechanical anisotropy and poor mechanical properties due to the combination of (meth)acrylate and epoxy functionalities, leading to inaccurate parts and reduced mechanical performance.

Innovation Solution

The development of interpenetrating polymer networks (IPNs) composed of vinyl ester and epoxy-amine components, where vinyl ester functionality is photopolymerized via free radical polymerization and epoxy functionality is thermally polymerized, forming a sequential cure using VPP methods.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If both (meth)acrylate and epoxy functionalities are combined in VPP resins to combine their advantages, then cure rate and mechanical properties are improved, but manufacturing precision and part accuracy deteriorate due to distortion

Engineering Contradiction:

Improvecure rateVSAvoidpart accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent segments the curing process into two distinct stages: first, photopolymerization of (meth)acrylate groups during VPP printing to achieve rapid initial curing; second, thermal polymerization of epoxy groups during post-processing to eliminate distortion and improve precision. This temporal segmentation allows each polymerization mechanism to contribute its advantages without the harmful effects of simultaneous operation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies preliminary action by performing photopolymerization of the (meth)acrylate component during the VPP printing process itself, creating an initial cured structure that maintains shape fidelity. The epoxy component is then thermally polymerized in a controlled post-processing step, allowing distortion-free curing that enhances precision without compromising the already-formed structure.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If epoxy resins are used with thermal curing procedures, then manufacturing precision and mechanical performance are improved, but productivity deteriorates due to prohibitively slow cure rates

Engineering Contradiction:

Improvegeometric accuracyVSAvoidcure rate

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent merges two different polymerization mechanisms—photopolymerization for (meth)acrylate groups and thermal polymerization for epoxy groups—into a single dual-functional resin system. This allows the material to benefit from both rapid light-induced curing during printing and precision-enhancing thermal curing during post-processing, combining the speed advantages of photopolymerization with the precision advantages of thermal epoxy curing.

Inventive Principle:

Principle #5Merging (Combining)

3Productivity

If (meth)acrylate-based resins are used for rapid polymerization, then productivity is improved with high cure rates, but manufacturing precision deteriorates leading to part distortion and weakened mechanical properties

Engineering Contradiction:

Improvecure rateVSAvoidgeometric accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

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

This approach enhances mechanical properties and accuracy of 3D printed parts by creating isotropic structures with improved glass transition temperatures, moduli, and toughness.

Implementation Method 1

the vinyl ester functionality is polymerized by photo-induced, free radical polymerization

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Implementation Method 2

the at least one epoxy functionality and the crosslinker are polymerized by thermal step-growth polymerization

Methodology Applied

Scientific EffectThermal polymerization:

Data Source

PatentUS12545755B2Network toughening of additively manufactured, high glass transition temperature materials via sequentially cured, interpenetrating polymers

Publication Date: 2026.02.10 UNITED STATES OF AMERICA THE AS REPRESENTED BY THE SEC OF THE ARMY

AI summary

Resins and formulations of individual monomers bearing both vinyl ester and epoxy functionality were either synthesized or formulated such that vinyl ester components capable of polymerizing by photo-induced, free radical polymerization were mixed with step-growth epoxy-amine systems, facilitating sequential cure. The vinyl ester component was photopolymerized using vat photopolymerization (VPP). Additionally, the preparation of bio-based photo curable thermosetting resins that have tailorable thermal and mechanical properties is provided. All monomers and polymers described herein are useful in a variety of applications, including additive manufacturing applications.