Lignin Polymer Particles for SLS Without Thermal Decomposition
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Solution Overview
Problem
Lignin's thermal instability and limited processing window pose challenges in additive manufacturing, particularly in selective laser sintering (SLS), leading to mechanical property dependence on fusion with other polymers and potential grain boundaries.
Innovation Solution
Forming highly spherical polymer particles by mixing thermoplastic polymers with lignin, a carrier fluid, and an emulsion stabilizer, then cooling and separating the mixture to create particles suitable for additive manufacturing methods like SLS, which mitigates warping and enhances mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lignin is incorporated into polymer composites for additive manufacturing, then material cost is reduced and renewable content is increased, but lignin decomposes at elevated temperatures and exhibits increased viscosity
Solution Approach 1:
The patent uses a carrier fluid as an intermediary medium to process lignin particles during selective laser sintering. The carrier fluid absorbs excess energy from the laser, preventing lignin decomposition while enabling effective sintering of the polymer particles. This intermediary approach allows lignin to be incorporated without suffering from its inherent thermal instability.
Solution Approach 2:
The patent changes the processing parameters by controlling the temperature and exposure time of lignin during additive manufacturing. By maintaining processing temperatures below lignin's decomposition point and using short exposure times, the patent enables lignin incorporation while avoiding viscosity increase and decomposition. The process operates in a optimized parameter window that preserves lignin's beneficial properties.
2Ease of operation
If lignin temperature is increased for processing, then lignin viscosity decreases and flowability improves, but lignin starts to decompose
Solution Approach 1:
The patent replaces thermal processing with a mechanical/emulsion-based approach. Instead of heating lignin to improve flowability, the patent uses an emulsion stabilization mechanism where lignin particles are suspended in a carrier fluid. This substitution allows lignin to be processed in a low-temperature state while maintaining adequate flowability through the emulsion system.
Solution Approach 2:
The carrier fluid acts as an intermediary that enables lignin processing without requiring high temperatures. The carrier fluid provides the necessary flow medium and energy absorption capacity, allowing lignin to be processed at temperatures below its decomposition point while maintaining adequate viscosity for additive manufacturing.
3Productivity
If lignin particles are fused to polymer particles in SLS, then composite objects can be printed, but grain boundaries are introduced and mechanical properties deteriorate
Solution Approach 1:
The patent creates a homogeneous distribution of lignin particles within the polymer matrix by using an emulsion stabilization approach. Instead of fusing discrete lignin particles to polymer particles (which creates grain boundaries), the lignin is uniformly distributed and stabilized within the polymer phase, eliminating interfacial weaknesses and improving overall mechanical properties.
Solution Approach 2:
The carrier fluid serves as an intermediary that enables uniform distribution of lignin particles during the sintering process. By controlling the interaction between lignin, polymer, and carrier fluid, the patent achieves a homogeneous composite structure without the formation of detrimental grain boundaries, thereby maintaining mechanical 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
The method produces polymer particles with improved mechanical properties and reduced warping, leveraging lignin's abundance and low cost while incorporating its beneficial properties like flame retardancy and antimicrobial effects.
Implementation Method 1
mixing a mixture comprising: a thermoplastic polymer, a lignin, a carrier fluid, and optionally an emulsion stabilizer at a temperature at or greater than a melting point or softening temperature of the thermoplastic polymer to emulsify a thermoplastic polymer melt in the carrier fluid
Implementation Method 2
cooling the mixture to below the melting point or softening temperature to form polymer particles
Implementation Method 3
exposing at least a portion of the first and second particles, when included, to a laser to fuse the first and second particles, when included, and form a consolidated body
Data Source
AI summary
Thermoplastic polymer particles suitable for use in additive manufacturing and related methods may comprise lignin. For example, said polymer particles may comprise a thermoplastic polymer, a lignin, optionally an emulsion stabilizer, and optionally a compatibilizer. Said polymer particles may be produced by melt emulsification methods and be highly spherical and, consequently, suited for selective laser sintering methods of additive manufacturing.