Polyamide Powder Viscosity Stability for Selective Sintering
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Solution Overview
Problem
Polyamide powders used in selective absorbing sintering (SAS) and selective inhibition sintering (SIS) processes face issues with aging, making them unusable after initial molding production, leading to increased costs and environmental impact, and resulting in inconsistent mechanical properties in the final products compared to selective laser sintering (SLS).
Innovation Solution
Development of polyamide powders with high initial viscosity and minimal viscosity increase over time, featuring excess amine or carboxylic acid end groups, open mesopores for homogeneous distribution of absorbers or inhibitors, and optimized pore volume distribution to prevent liquid runoff, allowing for repeated use and improved mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If polyamide powder is used in molding production 10 to 20 K below melting temperature, then molding production is achieved, but aging phenomena occur causing chain extension and making reprocessing impossible
Solution Approach 1:
The patent modifies the chemical composition parameters of the polyamide powder by incorporating specific end groups (amine or carboxylic acid) that stabilize the polymer chains against thermal degradation. This parameter change allows the powder to withstand repeated exposure to molding temperatures without irreversible chain extension, enabling multiple reuse cycles while maintaining consistent molding properties
Solution Approach 2:
The patent applies a protective chemical structure (specific end groups) to the polyamide powder before it undergoes thermal processing. This beforehand cushioning prevents the harmful aging effects from occurring during subsequent molding operations, allowing the powder to maintain its reprocessability throughout its service life
2Loss of substance
If polyamide powder is reused after molding production, then costs are reduced and environment is protected, but aging phenomena prevent reprocessing
Solution Approach 1:
The patent changes the chemical parameters of the polyamide by introducing stable end groups that prevent thermal degradation. This allows the powder to be reused multiple times without the chain extension that normally occurs during thermal processing, thereby reducing waste while maintaining ease of reprocessing
Solution Approach 2:
The patent transforms the polyamide powder from a single-use disposable material into a reusable material by modifying its chemical structure. Instead of being discarded after one use due to aging, the modified powder can be reused multiple times, reducing waste and improving sustainability
3Productivity
If molding is performed 10 to 20 K below melting temperature, then production efficiency is maintained, but amine and carboxylic acid end groups react causing chain extension
Solution Approach 1:
The patent modifies the chemical composition parameters by incorporating stable end groups into the polyamide structure. This parameter change prevents unwanted side reactions between amine and carboxylic acid end groups during molding, maintaining polymer chain stability even at reduced temperatures that preserve productivity
Solution Approach 2:
The patent converts the potentially harmful interaction between amine and carboxylic acid end groups into a beneficial feature by controlling their structure and reactivity. The modified end groups prevent harmful chain extension reactions while allowing the molding process to proceed efficiently at optimized temperatures
4Manufacturing precision
If absorber and inhibitor are applied in dissolved or dispersed form in liquid, then material selectivity is achieved, but liquid may flow away horizontally or vertically
Solution Approach 1:
The patent utilizes the porous structure of the polyamide powder particles to absorb and retain the liquid containing absorber and inhibitor. The pores capture the liquid within the particle structure, preventing it from flowing away horizontally or vertically, while still allowing the liquid to be absorbed by the printed material for selective sintering control
Solution Approach 2:
The patent applies the absorber and inhibitor locally to specific areas of the powder bed through liquid deposition. The liquid is applied only where needed on the powder surface, and the porous structure ensures it remains localized rather than spreading to unwanted areas, achieving manufacturing precision while preventing runoff
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 polyamide powders can be reused, reducing costs and environmental impact while enhancing the mechanical properties of molded products, such as elongation at break, compared to traditional SLS methods.
Implementation Method 1
open mesopores for homogeneous distribution of absorbers or inhibitors, and optimized pore volume distribution to prevent liquid runoff
Implementation Method 2
In the SAS method, the absorption of the material in contact with the absorber is increased
Implementation Method 3
the inhibitor retards the melting
Implementation Method 4
aging phenomena can occur. In this context, the amine and carboxylic acid end groups react with one another and cause extension of the polyamide chains
Data Source
AI summary
A polyamide powder for selective absorbing sintering, SAS, or selective inhibition sintering, SIS. The polyamide powder has a solution viscosity to ISO 307 of 1.8 to 2 and a rise in the solution viscosity of 0% to 25% when it is subjected to a temperature 20° C. below its melting temperature under air for 20 hours.