Selective Laser Sintering of Partially Cured Thermosetting Resins
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Solution Overview
Problem
Current selective laser sintering (SLS) technologies face challenges in printing thermosetting materials due to their amorphous nature, which prevents them from being directly printed and cured, resulting in re-melting of printed parts, and existing strategies rely on high filler loadings or rapid cure kinetics, leading to short shelf-life and deformation issues.
Innovation Solution
A method involving the use of partially cured resin materials, comprising a stoichiometrically balanced thermosetting resin and curing agent, printed near the glass transition temperature and then cured using a sub-Tg schedule to achieve gelation and subsequent crosslinking without deformation, allowing for the production of unfilled, high Tg thermosets that can be printed and cured without deforming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thermosetting materials are printed by SLS using conventional approaches, then printing can be achieved, but the materials re-melt during curing and deformation occurs
Solution Approach 1:
The resin is partially cured before printing to achieve a pre-gelled state with sufficient structural integrity to maintain shape during the printing process and subsequent complete curing, preventing re-melting and deformation
Solution Approach 2:
The curing process is controlled by changing temperature parameters - the printed part is cured at temperatures below the glass transition temperature (Tg) to achieve gelation and crosslinking without causing re-melting or deformation
2Ease of manufacture
If high filler loadings are used to enable printing of thermosetting materials, then printability is improved, but shelf-life is reduced and deformation issues occur
Solution Approach 1:
The invention removes the need for high filler loadings by using a resin-centric approach with controlled partial curing, achieving printability through chemical modification of the resin itself rather than relying on filler reinforcements
Solution Approach 2:
The resin formulation is modified by controlling the degree of conversion during partial curing to achieve optimal printability without requiring high filler content, thereby maintaining long shelf-life
3Ease of manufacture
If rapid cure kinetics are used to achieve gelation during printing, then printing is enabled, but shelf-life becomes short and deformation occurs
Solution Approach 1:
The resin is pre-modified through partial curing to achieve gelation at an controlled rate during printing, preventing premature crosslinking that would reduce shelf-life while still enabling successful printing
Solution Approach 2:
The cure kinetics are controlled by adjusting the partial curing degree and curing temperature parameters to achieve gelation at the optimal rate - fast enough for printing but slow enough to maintain shelf-life
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
Enables the successful printing and curing of thermosetting materials by SLS, maintaining shape during post-print cure and minimizing deformation, with a long shelf-life and improved mechanical properties, using a resin-centric approach that avoids the limitations of filler-based methods.
Implementation Method 1
Selective laser sintering (SLS) is an additive manufacturing, 3-D printing technique in which polymer powders are sintered together layer-by-layer with a laser to produce a printed solid object
Implementation Method 2
The laser selectively fuses the powdered material by scanning cross-sections generated from a 3-D digital description of the object on the surface of a powder bed
Implementation Method 3
curing the printed part according to a cure schedule to provide a cured printed part... curing the printed part at a temperature below the glass transition temperature until gelation is reached
Implementation Method 4
curing the printed part at a temperature above the glass transition temperature... to provide a cured printed part with a three-dimensional crosslinked network
Implementation Method 5
printing and sintering the resin powder on a print bed at a bed temperature near a glass transition temperature of the resin powder to provide a printed part
Data Source
AI summary
The invention is directed to a method of controlled conversion of thermosetting resins and additive manufacturing thereof by selective laser sintering. Partial curing of a thermosetting formulation can be used to increase the Tg of the resin and minimize the additional cure needed to cross-link a printed object. After printing, the partially cured material is finally cured via a slow temperature ramp maintained just below the material's evolving Tg.