Water-Based Primer-Surfacer for Additive Manufacturing Surface Leveling
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Solution Overview
Problem
Additively manufactured parts often have rough surface features due to layer-by-layer fabrication, leading to surface defects like mud cracking and shrinking, which are difficult to smooth using conventional mechanical methods without introducing new defects.
Innovation Solution
A two-part primer-surfacer coating system comprising a carboxyl-functional polyurethane prepolymer, acrylic copolymer, or polyester polyol, combined with a polyaziridine or carbodiimide crosslinker, applied to smooth and level the surface, providing excellent adhesion to both polymeric substrates and topcoats while avoiding surface defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If mechanical smoothing methods are used on additively manufactured parts, then surface roughness is reduced, but surface defects such as mud cracking and shrinking are introduced
Solution Approach 1:
The patent replaces mechanical smoothing methods with a chemical coating system. Instead of mechanically abrading the surface (which causes mud cracking and shrinking), a primer-surfacer coating is applied that chemically fills and levels the surface profile through curing, eliminating mechanical contact and associated defects
Solution Approach 2:
The patent changes the surface treatment approach from mechanical removal of material to chemical addition and transformation. The coating composition undergoes chemical changes during curing (crosslinking reactions) that transform the rough surface into a smooth, defect-free finish
2Shape
If a primer-surfacer coating is applied to fill surface profiles, then surface smoothness is improved, but adhesion to polymeric substrates and topcoats must be maintained
Solution Approach 1:
The patent uses a composite coating system comprising multiple components (carboxyl-functional polyurethane prepolymer, acrylic copolymer, polyester polyol, and crosslinker) that work together to provide both surface filling capability and adhesion. The combination of different polymer chemistries and crosslinking mechanisms creates a coating that simultaneously achieves surface leveling and strong bonding to substrates and topcoats
Solution Approach 2:
The patent provides different functional properties at different interfaces: the coating formulation is designed to adhere to the polymeric substrate at the bottom interface while simultaneously providing a smooth, level surface for subsequent topcoat application at the top interface, with each function achieved through specific compositional elements
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 system effectively levels surface features, enhances adhesion, and achieves high film thickness without defects, meeting aerospace performance standards, and can be used in additive manufacturing to improve the finish of complex parts.
Implementation Method 1
The compositions are based on carboxylic acid and aziridine or carbodiimide curing chemistries
Implementation Method 2
Water-based primer-surfacer and uses thereof
Data Source
AI summary
Water-based compositions useful as primer-surfacer precursor compositions and primer-surfacer coatings are disclosed. The compositions are based on carboxylic acid and aziridine or carbodiimide curing chemistries. The primer-surfacer coating exhibit excellent adhesion to polymeric substrates and to water-based or solvent-based topcoats. The primer-surfacer compositions can be used to level surfaces.