Thermoplastic Polyurethane Surface Treatment via Impregnation
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Solution Overview
Problem
Additive manufactured objects made from thermoplastic polyurethane using powder bed fusion methods often have rough and porous surfaces, which affect their mechanical properties and susceptibility to contaminants, and existing surface treatment methods either fail to fully address these issues or have environmental drawbacks.
Innovation Solution
A method involving partial or complete contact of the object with an aqueous polyurethane dispersion and water-dispersible polyisocyanate treating agent, under controlled pressure and temperature conditions, to enhance surface smoothness and mechanical properties, with the treating agent comprising 36% to 70% solid polyurethane dispersion and 4% to 8% water-dispersible polyisocyanate by weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If grinding and/or polishing the surface of the additive manufactured object, then the surface smoothness is improved, but the pores cannot be effectively eliminated and the geometry of the object may be changed
Solution Approach 1:
The patent uses an impregnating agent as an intermediary substance that penetrates into the porous structure of the additive manufactured object. This agent fills the pores and bonds with the material, smoothing the surface and sealing pores without requiring mechanical contact that would alter the object's geometry. The impregnating agent acts as a mediator between the porous surface and the desired smooth, pore-free finish.
2Manufacturing precision
If using organic solvents to treat the porous surface, then the porosity is eliminated and surface is smoothed, but the geometry of the object is changed and strong polar solvents require long removal time at high temperature
Solution Approach 1:
The patent changes the fundamental parameter of the treating agent from organic solvent to water-based impregnating agent. This substitution eliminates the need for high-temperature removal processes and prevents geometry changes. The water-based agent achieves pore elimination and surface smoothing through controlled impregnation and evaporation at lower temperatures, fundamentally altering the treatment approach while maintaining effectiveness.
3Manufacturing precision
If polishing the surface of the object, then the surface becomes smoother, but material is abraded from the surface and the geometry of the object may be changed
Solution Approach 1:
The impregnating agent serves as an intermediary that deposits material into and on the porous surface rather than removing material through abrasion. This additive approach to surface treatment fills pores and smooths the surface by adding bonding material, contrasting with the subtractive polishing approach that removes surface material and risks geometry changes.
4Manufacturing precision
If using aqueous polyurethane dispersion and water-dispersible polyisocyanate as treating agent, then the surface finish and mechanical properties are improved while being environmentally friendly, but the treating agent composition must be precisely controlled
Solution Approach 1:
The patent establishes specific parameter ranges for the impregnating agent composition: water content of 30-70% by weight and polyisocyanate content of 3-15% by weight. These controlled parameters ensure optimal penetration into the porous structure, adequate bonding strength, and proper surface finish. The defined ranges balance environmental friendliness with effective pore elimination and mechanical property enhancement.
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 improves the surface finish and mechanical properties of additive manufactured objects, such as tensile strength and elongation at break, while being environmentally friendly and avoiding the use of organic solvents.
Implementation Method 1
bringing the object completely or partly into contact with a treating agent; leaving the object at 10°C-30°C and 100 mbar-800 mbar for 3-10 minutes
Implementation Method 2
heat-treating the object at a temperature of 70°C-90°C after returning to normal pressure
Implementation Method 3
the treating agent comprises an aqueous polyurethane dispersion and a water-dispersible polyisocyanate
Data Source
AI summary
The present invention relates to a method for producing an at least partially coated object and to an at least partially coated object obtained by the method. The method comprises bringing the object completely or partly into contact with a treating agent; leaving the object at 10°C-30°C and 100 mbar-800 mbar for 3-10 minutes; and heat-treating the object at a temperature of 70°C-90°C after returning to normal pressure; wherein the object is produced from a construction material by means of an additive manufacturing method, and the construction material comprises a thermoplastic polyurethane; and wherein the treating agent comprises an aqueous polyurethane dispersion and a water-dispersible polyisocyanate, and the viscosity of the treating agent is 100 mPa·s-550 mPa·s; and wherein the amount of the solid constituent of the aqueous polyurethane dispersion is 36% by weight to 70% by weight, and the amount of the solid constituent of the water-dispersible polyisocyanate is 4% by weight to 8% by weight, relative to the total weight of the treating agent. The at least partially coated object of the present invention has good mechanical properties and good surface effect.