Polyurethane Resin Crystallization Inhibition for Additive Manufacturing
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Solution Overview
Problem
3D printing resins containing UV curable polyurethane oligomers often experience crystal formation over time, which is difficult to reverse due to high melting points, leading to shelf life issues.
Innovation Solution
Incorporating low percentages of crystallization inhibitors such as amino alcohols, amines, ureas, salts, and polymers like PVP into the resin composition to inhibit crystal growth, along with a reactive prepolymer and monomer system that includes photoinitiators and a heat polymerizable component for dual cure additive manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UV curable polyurethane oligomers are used as 3D printing resins, then the resin can be polymerized through UV light to form 3D objects, but crystal formation occurs in the resin over time leading to shelf life issues
Solution Approach 1:
Crystallization inhibitors are introduced as intermediary substances that interfere with the crystallization process of polyurethane oligomers. These inhibitors (such as PVP, amino alcohols, amines, ureas, or salts) act as mediators between the polyurethane molecules, preventing them from organizing into crystalline structures while maintaining the resin's UV curability and other essential properties.
Solution Approach 2:
The chemical composition parameters of the resin system are modified by adding crystallization inhibitors at specific concentrations (0.01-10 wt%). This parameter change alters the molecular interactions in the resin, raising the cloud point temperature and preventing crystal formation at storage temperatures, thereby extending shelf life without compromising the photopolymerization capability.
2Stability of the object's composition
If crystal formation occurs in the resin, then the resin structure becomes stable, but the crystals are difficult to reverse to liquid form due to high melting point
Solution Approach 1:
Crystallization inhibitors are added to the resin formulation in advance to prevent crystal formation before it occurs. By preemptively introducing these inhibitors, the resin maintains its liquid state during storage and processing, avoiding the formation of high-melting-point crystals that would be difficult to reverse. The inhibitors continuously counteract the tendency toward crystallization throughout the resin's shelf life.
3Reliability
If crystallization inhibitors are added to prevent crystal formation, then shelf life is improved, but the resin composition becomes more complex
Solution Approach 1:
The crystallization inhibitors used are selected from commercially available, cost-effective substances such as PVP, amino alcohols, amines, ureas, and salts. These relatively simple and inexpensive additives are incorporated in small amounts (0.01-10 wt%) to achieve the desired shelf life extension, minimizing the impact on overall resin composition complexity and formulation cost.
Data Source
AI summary
A resin composition useful for additive manufacturing is provided, which resin composition may exhibit improved shelf life through inhibition of crystallization. Such resin composition may include a crystallization inhibitor as taught herein, and/or a prepolymer produced by reaction of an isocyanate with multiple isomers and comprising a lower percentage of the structurally symmetric isomer. Methods of forming a three-dimensional object using such resin composition are also provided.