Core-Shell Polyamide Powder for Laser Sintering
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Solution Overview
Problem
Polyamide powders used in laser beam agglomeration technologies face challenges with deformation and poor geometric definition due to a narrow melting to crystallization temperature gap, which limits the precision and quality of manufactured parts.
Innovation Solution
Development of a new seeded polyamide powder with a shell and core structure made of PA6, PA12, or PA6/12, where the shell and core can have the same or different molecular masses, produced through anionic polymerization with specific catalysts, activators, and organic fillers, enhancing the Tf-Tc difference for improved processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyamide powder with narrow melting to crystallization temperature gap is used, then manufacturing process is simpler, but deformation phenomena occur during manufacturing reducing geometric definition
Solution Approach 1:
The invention changes the thermal parameters of the polyamide powder by selecting specific polyamide types (PA6, PA12, or PA6/12 blends) with optimized molecular weights and compositions. This creates a widened temperature gap between melting point (Tf) and crystallization point (Tc), allowing the powder to remain in a stable plastic state longer during laser sintering, thereby preventing deformation and improving geometric definition while maintaining manufacturing simplicity
Solution Approach 2:
The invention uses composite polyamide formulations, specifically blends of PA6 and PA12 in various ratios, or core-shell structured particles with different polyamide compositions. These composite structures provide optimized thermal properties with enhanced fusion enthalpy and widened Tf-Tc gap, resolving the contradiction between ease of manufacture and manufacturing precision
2Use of energy by moving object
If polyamide powder with low fusion enthalpy is used, then energy consumption is reduced, but geometric definition of manufactured parts deteriorates
Solution Approach 1:
The invention optimizes the molecular weight and molecular weight distribution of the polyamide components, as well as the composition ratios in blends or core-shell structures. This tuning of molecular parameters increases the fusion enthalpy (ΔHf) to enhance geometric definition during laser sintering, while the process remains energy-efficient due to the optimized thermal characteristics of the specific polyamide formulations
3Productivity
If cooling rate is increased to prevent deformation, then manufacturing time is reduced, but deformation phenomena increase due to rapid temperature drop below crystallization point
Solution Approach 1:
The invention changes the crystallization kinetics parameters of the polyamide powder through careful selection of polyamide type, molecular weight, and composition. The optimized materials exhibit slower crystallization rates and wider Tf-Tc gaps, allowing controlled cooling without rapid temperature drops below Tc. This enables faster manufacturing cycles while preventing deformation caused by rapid cooling, thus improving both productivity and geometric definition
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 enhanced Tf-Tc difference in the new polyamide powder improves the geometric definition of manufactured parts by reducing deformation and increasing the fusion enthalpy, leading to higher precision and quality in 3D object creation.
Implementation Method 1
anionic polymerization of lactam monomer, caprolactam or their mixture
Implementation Method 2
an amide of formula R1-NH-CO-R2... the proportion of this compound being between 0.001 mol and 0.1 mol per 1000 g of monomers
Implementation Method 3
seeded with an organic filler... said filler being particles of finely divided PA12 or PA6 powder
Implementation Method 4
The seeded powder, obtained at the end of the polymerization, is insoluble in the lactam solvent previously introduced into the reaction medium
Implementation Method 5
A thin layer of polyamide powder is deposited on a horizontal plate held in an enclosure heated to a temperature located between the crystallization temperature (Tc) and the melting temperature (Tf) of the polyamide powder. The laser agglomerates powder particles
Implementation Method 6
laser agglomerates powder particles at different points of the powder layer according to a geometry corresponding to the object
Implementation Method 7
the melting temperature (Tf) of the polyamide powder... immediately after the action of the laser beam, the temperature of the sample is higher than the crystallization temperature (Tc)
Implementation Method 8
the addition of a new layer of Colder powder quickly drops the room temperature below (Tc) and causes deformation... the object solidifies as soon as its temperature drops below the crystallization temperature (Tc)
Data Source
AI summary
The invention relates to a seeded particle of polyamide (PA) powder composed of a shell made of PA-6, PA-12 or PA-6/12 and of a core made from PA-6, PA-11, PA-12, PA-6/12, PA-6,12, PA-6,6, PA-8 or PA-4, the core and the shell being either of identical polyamide nature but of different molecular weight or of different polyamide nature. The particle for which the shell has a melting temperature Tf1 and a crystallization temperature Tc1 and for which the core has a melting temperature Tf2 and a crystallization temperature Tc2 is characterized in that the difference in absolute values between Tf1 - Tc1 and/or between Tf2 - Tc2 is greater than the difference in absolute values between the melting temperature and the crystallization temperature of a particle of powder seeded by a mineral filler and for which the shell is made of PA-6, PA-12 or PA-6/12.