Semi-crystalline Polymer Blends for Additive Manufacturing
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Solution Overview
Problem
Additive manufacturing techniques face challenges in printing dimensionally stable 3D parts using semi-crystalline polymers due to residual stresses and discontinuous volume changes, which lead to issues like curling and sagging, especially in extrusion-based methods where controlling crystallization kinetics is difficult.
Innovation Solution
A method involving blends of semi-crystalline polymers with secondary materials that control crystallization kinetics by retarding or accelerating crystallization, using miscible amorphous polymers or additives to manage heat of fusion and enthalpy, allowing for reduced residual stresses and improved bonding between layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If semi-crystalline polymers are used for additive manufacturing, then mechanical properties and dimensional stability are improved, but residual stresses and volume changes cause curling and sagging
Solution Approach 1:
The patent modifies the crystallization parameters of semi-crystalline polymers by controlling cooling rates, temperatures, and time durations during and after printing. By adjusting these parameters, the patent optimizes crystallization kinetics to reduce residual stresses and volume changes while maintaining mechanical properties, thereby preventing curling and sagging issues.
Solution Approach 2:
The patent applies preliminary heating or pre-conditioning to the semi-crystalline polymer material before the printing process begins. This preliminary action prepares the material's crystallization behavior in advance, ensuring more uniform crystallization during printing and reducing subsequent residual stresses and dimensional instability.
2Manufacturing precision
If crystallization kinetics are controlled to reduce residual stresses, then dimensional stability is improved, but printing speed and productivity may be reduced
Solution Approach 1:
The patent applies partial crystallization control during the printing process, focusing on critical regions or stages where dimensional stability is most affected. By not requiring complete or uniform crystallization control throughout the entire material and process, the patent maintains faster printing speeds while still achieving sufficient dimensional stability in key areas.
Solution Approach 2:
The patent implements periodic or staged crystallization control during printing, alternating between faster deposition phases and controlled crystallization phases. This periodic approach allows the printing process to maintain overall speed while periodically applying crystallization control to ensure dimensional stability, balancing productivity with precision.
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 enables the production of 3D items with mechanical properties similar to semi-crystalline polymers while reducing residual stresses, preventing curling and sagging, and allowing for annealing to enhance crystallinity and stability.
Implementation Method 1
The extruded part material fuses to previously deposited part material, and solidifies upon a drop in temperature
Implementation Method 2
when the secondary material is combined with the semi-crystalline polymer to form a blend having an enthalpy that is between about 2 J/g heat of fusion and about 80% of the heat of fusion of the neat semi-crystalline polymer
Implementation Method 3
A plasticizer in the range of about 5 wt. % and about 30 wt. % is added to reduce a glass transition temperature to a range between about 20° C. and about 45° C.
Data Source
AI summary
A polymeric material includes a semi-crystalline polymer and a secondary material wherein when the secondary material is combined with the semi-crystalline polymer to form a blend having at least a 3° C. reduction in a hot crystallization temperature relative to the neat semi-crystalline polymer.