3D Printed TPU Surface Modification via Solvent Swelling
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Solution Overview
Problem
Articles produced using thermoplastic polyurethane (TPU) in 3D printing processes have porous surfaces, leading to elevated wear, susceptibility to dirt adhesion, and negative effects on aesthetics and haptics, as well as potential water absorption that can compromise the structure and stability of the articles.
Innovation Solution
A process involving the partial contact of TPU-comprising articles with a first liquid containing ≥80% by weight of a polar aprotic solvent, followed by contact with a second liquid containing ≥80% by weight of a polar protic solvent, to enhance mechanical properties and surface smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a porous surface structure is used in 3D printed articles, then manufacturing ease is improved, but wear resistance deteriorates and dirt adhesion increases
Solution Approach 1:
The patent applies parameter changes by modifying the surface properties of the porous 3D printed article through controlled exposure to liquid preparations. The surface is treated with a preparation containing specific compounds (NCO-comprising compounds, OH-comprising polymers, or their combinations) to alter the surface chemistry and morphology. This transforms the surface from highly porous and rough to modified with improved wear resistance and reduced dirt adhesion, while maintaining the bulk porous structure for manufacturing ease.
Solution Approach 2:
The patent employs composite materials by combining the original porous TPU article with surface-modifying layers or coatings. The treatment creates a composite structure where the bulk material remains porous for ease of manufacture, while the surface acquires enhanced properties through the interaction with the liquid preparation containing NCO-compounds and OH-polymers, forming a composite surface layer with improved wear and adhesion characteristics.
2Ease of manufacture
If a porous surface structure is used in 3D printed articles, then manufacturing ease is improved, but haptic quality deteriorates
Solution Approach 1:
The patent applies parameter changes by modifying the surface morphology and chemistry through controlled liquid treatment. The surface is exposed to a preparation containing NCO-comprising compounds and/or OH-comprising polymers, which alters the surface parameters to reduce porosity and smooth the texture. This improves haptic quality by eliminating the uncomfortable roughness of highly porous surfaces while preserving the ease of manufacture through the bulk porous structure.
3Manufacturing precision
If aqueous polyurethane dispersion is used for surface treatment, then surface smoothness is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies the principle of using cost-effective, easily applicable surface treatments. Instead of using expensive aqueous polyurethane dispersions, the invention employs simpler, more economical liquid preparations containing NCO-comprising compounds and/or OH-comprising polymers. These cheaper alternatives achieve the desired surface smoothness and improved haptics through a straightforward application process, significantly reducing manufacturing costs while maintaining surface quality.
Solution Approach 2:
The patent applies parameter changes by using cost-effective liquid preparations with specific chemical compositions (NCO-compounds and OH-polymers) to modify the surface properties. The treatment changes the surface parameters to achieve smoothness and improved haptics through a simple application and drying process, avoiding the need for expensive aqueous polyurethane dispersions while maintaining effective surface modification.
4Ease of manufacture
If porous surface is used in TPU articles, then ease of manufacture is improved, but water absorption increases affecting structural stability
Solution Approach 1:
The patent applies parameter changes by modifying the surface chemistry and porosity through controlled liquid treatment. The surface is exposed to a preparation containing NCO-comprising compounds and/or OH-comprising polymers, which alters the surface parameters to reduce water absorption. This creates a water-resistant surface layer that maintains the bulk porous structure for ease of manufacture while protecting against water-induced structural degradation.
Solution Approach 2:
The patent employs composite materials by creating a layered structure where the bulk TPU article maintains its porous manufacturing advantages, while the surface forms a modified composite layer through interaction with the liquid preparation. This composite surface layer has reduced water absorption properties, protecting the article's structural stability without compromising the ease of manufacture of the underlying porous structure.
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 process results in articles with improved tensile strength, breaking elongation, and a smoother surface, while minimizing the residual weight fraction of the first liquid to <5%, thereby addressing the issues of wear, adhesion, and structural integrity.
Implementation Method 1
the build material is at least partially contacted with a first liquid which contains ≥80% by weight based on the total weight of the first liquid of a polar aprotic solvent... the first liquid swells the build material
Implementation Method 2
contacting for a second predetermined duration the regions of the build material contacted with the first liquid in step II) with a second liquid which contains ≥80% by weight based on the total weight of the second liquid of a polar protic solvent... the second liquid removes the first liquid from the build material
Data Source
AI summary
The invention relates to a method for modifying an object comprising the step of: I) providing an object which is made at least partially of a construction material comprising a thermoplastic polyurethane. The method also comprises the following steps: II) contacting, at least in part, the construction material, for a first predetermined period of time, with a first liquid comprising ≥80% by weight, based on the total weight of the first liquid, of a polar aprotic solvent; III) contacting, for a second predetermined period of time, the areas of the construction material that were in contact with the liquid in step II) with a second liquid comprising ≥80% by weight, based on the total weight of the second liquid, of a polar protic solvent. Preferably, the first liquid is DMSO or acetone and the second liquid is water.