UV-Curable Polythioether Sealants for Aircraft Surface Smoothing
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Solution Overview
Problem
Aerospace sealants face challenges in efficiently smoothing and electrically insulating surface defects on aircraft, particularly due to the large number of fasteners and panel gaps, which require high-volume production methods that meet demanding aerospace requirements.
Innovation Solution
The use of UV-curable sealant compositions comprising thiol-terminated polythioethers and alkenyl-terminated compounds, which are applied to surface defects, smoothed, and cured using ultraviolet radiation, providing a planarized and insulated surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional sealant compositions and methods are used, then surface defects can be filled, but the process is not amenable to high-volume production and requires manual smoothing operations
Solution Approach 1:
The patent replaces manual mechanical smoothing operations with UV photopolymerization. The sealant composition contains photoinitiators that activate upon UV exposure, causing the material to cure and maintain its smoothed shape without requiring manual intervention. This substitutes the mechanical smoothing process with a chemical/photochemical curing process that can be automated and scaled for high-volume production.
Solution Approach 2:
The patent applies the sealant composition to surface defects and smooths it before UV curing. By performing the smoothing operation on the uncured, moldable material first, the process enables automated application and smoothing followed by rapid UV curing. This preliminary smoothing action on uncured material allows for high-volume production while maintaining surface quality.
2Productivity
If UV-curable sealant compositions are used, then high-volume production is enabled, but the sealant must meet demanding aerospace requirements for flexibility, fuel resistance, and adhesion
Solution Approach 1:
The patent uses a composite sealant composition comprising polythioether polymer, polyene, and photoinitiator. The polythioether polymer provides flexibility and fuel resistance, the polyene enables crosslinking through thiol-ene chemistry for enhanced mechanical properties, and the photoinitiator enables UV curing for high-volume production. This composite material system simultaneously meets aerospace performance requirements and enables automated manufacturing.
Solution Approach 2:
The patent utilizes the thiol-ene click chemistry reaction between polythioether and polyene, which can be controlled through UV exposure parameters. By adjusting UV intensity, exposure time, and photoinitiator concentration, the curing process can be optimized to achieve complete crosslinking while maintaining material flexibility and adhesion properties required for aerospace applications.
3Manufacturing precision
If manual smoothing methods are used, then surface defects can be filled, but the process is time-consuming and not efficient for aircraft with thousands of fasteners
Solution Approach 1:
The patent replaces time-consuming manual smoothing operations with rapid UV photopolymerization. The uncured sealant is applied and smoothed, then UV exposure triggers rapid crosslinking and curing, locking in the smoothed surface geometry. This reduces processing time from minutes per defect to seconds per defect, making the process efficient for aircraft with thousands of fasteners while maintaining surface smoothing quality.
Solution Approach 2:
The patent employs a periodic process sequence: apply uncured sealant, smooth surface, expose to UV radiation for curing. This periodic cycle of application, smoothing, and UV curing enables rapid processing of multiple defects in sequence, significantly reducing total processing time compared to traditional manual methods while maintaining consistent surface quality across all defects.
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 solution effectively fills and smooths surface defects, offering improved aerodynamic performance and electrical insulation while meeting the requirements for flexibility, fuel resistance, and adhesion necessary for aerospace applications.
Implementation Method 1
exposing the smoothed sealant composition to ultraviolet radiation to cure the smoothed sealant composition
Data Source
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AI summary
The present invention provides a method of smoothing a surface defect comprising: applying a sealant composition to the surface defect; smoothing the sealant composition to fill the surface defect; exposing the smoothed sealant composition to ultraviolet radiation to cure the smoothed sealant composition, wherein the sealant composition is UV-curable and comprises: (i) a thiol-terminated polythioether; and (ii) an alkenyl-terminated compound comprising a polyvinyl ether and/or a polyallyl compound.