3D Printed Polymer Articles with Isotropic Strength
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Solution Overview
Problem
3D printed parts made with thermoplastic polymers often exhibit weak mechanical properties due to poor layer-to-layer adhesion, leading to asymmetry in mechanical performance between the XY and Z directions, and poor elastomeric properties.
Innovation Solution
The use of semicrystalline and amorphous polymers with a specific stiffening temperature (G′/G″ crossover temperature) of less than 140°C, which enhances material mobility during printing, resulting in improved interpenetration of polymer layers and increased layer adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional thermoplastic polymers are used for 3D printing, then the printing process is simple and fast, but the layer-to-layer adhesion is poor and mechanical properties are weak
Solution Approach 1:
The patent changes the thermal parameters of the polymer material by selecting materials with specific glass transition temperatures (Tg) and melting points, as well as controlled crystallization rates. This allows the material to maintain mobility at printing temperatures for good layer adhesion, then stiffen appropriately after deposition to maintain structural integrity.
Solution Approach 2:
The patent exploits phase transitions of the polymer material - specifically the transition from rigid to mobile state during printing, and from mobile to rigid state after deposition. This enables the material to be deposited in a mobile state for good layer adhesion, then transition to a rigid state to provide mechanical strength.
2Device complexity
If amorphous or semi-crystalline polymers are used for 3D printing, then the material structure is simple, but the parts are anisotropic with poor performance in the Z direction
Solution Approach 1:
The patent changes the thermal and rheological parameters of the polymer to achieve optimal printability and isotropic properties. Specifically, materials with Tg between 50-150°C and melting points between 100-200°C are selected, along with controlled viscosity and crystallization rates, to enable good layer adhesion and isotropic mechanical properties.
Solution Approach 2:
The patent uses composite polymer systems that combine amorphous and semi-crystalline phases, or blends of different polymers, to achieve both ease of processing and isotropic mechanical properties. The composite structure allows the material to exhibit desired rheological behavior during printing while providing uniform mechanical properties in all directions.
3Strength
If polymers with high material mobility during printing are used, then layer adhesion is improved, but the material may not maintain structural integrity after cooling
Solution Approach 1:
The patent changes the thermal parameters of the polymer to achieve a balance between printability and structural integrity. Materials with specific Tg and melting point ranges are selected so that they remain mobile during printing for good adhesion, then stiffen appropriately after cooling to maintain structural integrity.
Solution Approach 2:
The patent creates a dynamic material system that transitions from a mobile state during printing to a rigid state after deposition. This dynamic behavior allows the material to exhibit high mobility when needed for layer adhesion, then transitions to a stable rigid state to provide structural integrity.
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 leads to 3D printed parts with high elongation at break in the Z direction, comparable to the XY direction, improved impact resistance, and enhanced robustness, making them suitable for applications requiring isotropic mechanical properties.
Implementation Method 1
The materials of the invention all have higher material mobility (as measured by melt rheology) at layer interfaces during printing
Implementation Method 2
semicrystalline and amorphous polymers having a select stiffening temperature at the print conditions
Data Source
AI summary
The invention relates to 3D printed parts made with thermoplastic polymers having a low stiffening temperature. 3D printed parts of the invention have very good Z layer adhesion, have a high elongation at break in the Z direction, preferably of more than 50 percent, and have at least an 80 percent ratio of Z to XY stress at yield or at break. The resulting part may be nearly isotropic—having similar mechanical properties in the XY and Z print directions. The excellent layer adhesion makes the resultant printed part more robust—able to withstand many cycles of use. Certain polymers of the invention produce printed parts that have a very low haze, and are nearly transparent.