Radiation Curable Resin Composition for High Modulus and Impact Resistance
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Solution Overview
Problem
Current radiation-curable resin compositions for stereolithography struggle to achieve a balance between high tensile modulus and impact resistance, often resulting in materials with either low toughness or low modulus, failing to meet the mechanical properties required for durable three-dimensional parts with complex geometries.
Innovation Solution
A radiation curable composition comprising a cationically polymerizable component, a cationic photoinitiator, a hydroxy component, and an impact modifier, with specific ratios of epoxy to hydroxy and aromatic to cycloaliphatic content, which after full cure, exhibits a tensile modulus of greater than 2 GPa, yield stress less than 70 MPa, and a K1c value or Izod value within specified ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If radiation curable resin compositions are formulated to achieve high tensile modulus, then the stiffness and structural integrity of three-dimensional parts are improved, but the impact resistance and toughness deteriorate
Solution Approach 1:
The patent employs a composite resin system combining multiple polymer types (epoxy, polyester, polyamide) with complementary mechanical properties. The epoxy component provides high tensile modulus and stiffness, while the polyester and polyamide components contribute toughness and impact resistance. This multi-phase composite formulation resolves the contradiction by integrating materials with opposing mechanical strengths into a unified resin composition that achieves both high modulus and impact resistance simultaneously.
Solution Approach 2:
The patent systematically varies the proportions and ratios of different resin components (epoxy to polyester ratio, aromatic to cycloaliphatic ratio) to optimize the balance between tensile modulus and impact resistance. By adjusting these compositional parameters within specific ranges, the formulation achieves the target mechanical properties of >2 GPa tensile modulus while maintaining specified impact strength and crack propagation resistance, resolving the trade-off through precise parameter control.
2Productivity
If the resin composition is cured rapidly using high power UV lasers (800 mW and above), then the production speed and process efficiency are improved, but the temperature increases leading to part distortion and excessive color development
Solution Approach 1:
The patent modifies the resin composition's chemical structure and component ratios to alter its thermal and curing characteristics. By selecting specific epoxy, polyester, and polyamide components with appropriate glass transition temperatures and reactivity, the formulation enables rapid curing at reduced exothermic temperature rise. The aromatic to cycloaliphatic ratio control and molecular weight selection adjust the polymerization heat generation, allowing high-speed curing without excessive temperature increase that causes distortion or discoloration.
Solution Approach 2:
The patent introduces photoinitiators and catalysts as intermediary substances that facilitate efficient energy transfer during UV curing. These intermediaries enable the resin to cure rapidly under high power UV laser irradiation while controlling the rate of polymerization and heat generation. The photoinitiator system mediates between the UV energy input and the polymerization reaction, allowing fast curing speeds to be achieved without the harmful thermal effects that would otherwise result from direct high-energy irradiation.
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
The composition achieves a unique balance of high toughness and modulus, ensuring the produced three-dimensional parts have excellent mechanical properties, including high impact strength and resistance to crack propagation, making them suitable for durable custom and semi-custom parts with complex geometries.
Implementation Method 1
a cationic photoinitiator... in step (a), a layer of the radiation-curable composition... is cured with the aid of appropriate imaging radiation
Data Source
AI summary
The invention relates to a radiation curable resin composition comprising a cationically polymerizable component, a cationic photoinitiator, a hydroxy component, an impact modifier and wherein the resin composition after full cure has a modulus of >2 GPa; a yield stress <70 MPa; and a K1c value >1.3 MPa·(m)1/2 or an Izod value >0.45 J/cm. The resin composition can preferably be used in the preparation of three dimensional objects.