Amorphous Thermoplastic Additive Manufacturing via Semi-Crystalline Blends
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Solution Overview
Problem
Existing additive manufacturing methods using selective laser sintering (SLS) are limited by the need for crystalline or semi-crystalline polymers, which precludes the use of amorphous polymers with desirable properties like optical transparency and toughness.
Innovation Solution
A semi-crystalline blended polymer is created by mixing amorphous thermoplastic polymers with crystalline or semi-crystalline thermoplastic polymers in specific proportions and heat-treating them to achieve a semi-crystalline structure suitable for SLS, which reverts to an amorphous state after manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If crystalline or semi-crystalline polymers are used for selective laser sintering, then the manufacturing process can be performed, but the resulting articles lack desirable properties such as optical transparency, toughness and elongation before breakage
Solution Approach 1:
The invention uses composite materials by blending amorphous thermoplastic polymers with crystalline or semi-crystalline thermoplastic polymers in specific proportions (at least 20 wt% amorphous polymer). This composite approach allows the material to exhibit both the processability of crystalline polymers during SLS and the desirable mechanical properties of amorphous polymers in the final article.
Solution Approach 2:
The invention changes the compositional parameters of the polymer material by controlling the weight ratio of amorphous to crystalline polymer components. By adjusting this parameter (at least 20 wt% amorphous polymer), the material properties are optimized to enable both successful SLS manufacturing and superior mechanical performance including optical transparency and toughness.
2Strength
If amorphous polymers are used, then desirable properties such as optical transparency and toughness are achieved, but the selective laser sintering process cannot be performed
Solution Approach 1:
The invention creates a composite polymer system combining amorphous and crystalline polymers. The crystalline component provides the necessary melting behavior for SLS manufacturing, while the amorphous component (at least 20 wt%) imparts optical transparency and toughness to the final article.
Solution Approach 2:
The invention modifies the thermal and compositional parameters of the polymer blend to enable SLS processing. By controlling the amorphous polymer content (at least 20 wt%) and the blending ratio, the material achieves a balance between processability during manufacturing and desired mechanical properties in the finished product.
3Stability of the object's composition
If solvents are used to crystallize amorphous polymers, then crystallized polymer is obtained, but residual solvent remains that precludes use in biocompatible applications and requires environmental mitigation
Solution Approach 1:
The invention extracts and eliminates the harmful solvent step from the crystallization process. Instead of using solvents to induce crystallization, the method employs a solvent-free blend of amorphous and crystalline thermoplastic polymers, where the crystalline component naturally provides the necessary crystalline structure without introducing residual solvent contamination.
Solution Approach 2:
The invention replaces the problematic solvent-based crystallization method with a solid-state polymer blend approach. The crystalline polymer component serves as a permanent structural element rather than a temporary solvent, eliminating the need for solvent removal and environmental mitigation while maintaining biocompatibility.
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 allows for the additive manufacturing of amorphous polymeric articles with desirable properties without residual solvent, overcoming the limitations of previous methods.
Implementation Method 1
these semi-crystalline polymer blends when additive manufactured revert to substantially amorphous polymeric articles with the desirable properties of an amorphous polymer
Implementation Method 2
heat-treating sufficiently realizes a semi-crystalline thermoplastic polymer suitable for additive manufacturing processes such as SLS
Implementation Method 3
heat-treating the blended polymer at a temperature above the glass transition temperature of the amorphous polymer but below the melt temperature of the semicrystalline polymer for a time sufficient to crystallize the blended polymer
Implementation Method 4
heating and fusing the particles of the layer in a controlled manner by directed electromagnetic radiation
Implementation Method 5
selective laser sintering of thermoplastic polymers
Data Source
AI summary
A semi-crystalline blended polymer useful for additive manufacturing is comprised of an amorphous thermoplastic polymer and a thermoplastic semi-crystalline polymer, each of the polymers being essentially miscible in the other and being blended at a weight ratio of amorphous polymer/semi-crystalline polymer of greater that 1 to about 20. The semi-crystalline blended polymer displays a DSC melt peak enthalpy of at least about 3 joules/g. The semi-crystalline polymer may be made by blending the aforementioned polymers at the weight ratio and subject to heating between the melt temperature of the semi-crystalline polymer and the glass transition temperature of the amorphous polymer. The semi-crystalline blended polymer may revert to essentially an amorphous polymer when additive manufactured by fusing layers of said polymer powders together.