Polythioether Prepolymers with Bis(alkenyl) Ethers for Rapid Curing
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Solution Overview
Problem
Aerospace sealants require rapid curing, improved fuel resistance, and compatibility with high filler loads, but existing sulfur-containing polythioether prepolymers face challenges in achieving these properties while maintaining suitable viscosity for application.
Innovation Solution
Hydroxyl-containing bis(alkenyl) ethers are incorporated into the backbone of polythioether prepolymers, allowing for the development of compositions that cure rapidly and exhibit improved filler compatibility, even with high filler loads, by reacting polythiols with these ethers and divinyl ethers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sulfur atoms are included in the backbone of the prepolymer to improve fuel resistance, then fuel resistance is improved, but the curing speed may be compromised
Solution Approach 1:
The patent introduces hydroxyl-containing bis(alkenyl) ether groups at specific positions within the polythioether prepolymer backbone. These localized functional groups provide rapid curing capability without requiring sulfur atoms throughout the entire backbone structure, thus achieving fast curing while maintaining fuel resistance through the sulfur-containing polythioether backbone segments.
Solution Approach 2:
The patent creates a composite molecular structure combining sulfur-containing polythioether segments (for fuel resistance) with hydroxyl-containing bis(alkenyl) ether groups (for rapid curing). This molecular-level composite allows both properties to coexist: the sulfur atoms provide fuel resistance while the hydroxyl and alkenyl groups enable rapid curing reactions.
2Strength
If high loading of filler is included to improve physical properties, then physical properties are improved, but viscosity increases making the sealant difficult to apply
Solution Approach 1:
The hydroxyl-containing bis(alkenyl) ether groups act as intermediary functional groups that interact with both the filler particles and the polythioether backbone. These groups reduce interparticle friction and improve filler dispersion, serving as a molecular lubricant that allows high filler loading while maintaining low viscosity and ease of application.
Solution Approach 2:
The patent changes the chemical parameters of the prepolymer by incorporating hydroxyl and alkenyl functional groups, which alter the surface properties and intermolecular interactions. This changes the filler-polymer interface characteristics, reducing viscosity even at high filler concentrations while maintaining improved physical properties from the filler loading.
3Speed
If rapid curing is achieved by modifying the prepolymer structure, then curing speed is improved, but filler compatibility may be compromised
Solution Approach 1:
The hydroxyl-containing bis(alkenyl) ether groups perform multiple functions simultaneously: the alkenyl groups participate in rapid curing reactions (providing curing speed), while the hydroxyl groups interact with filler surfaces (providing filler compatibility). This multi-functionality allows a single structural modification to achieve both rapid curing and maintained filler compatibility.
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 resulting sealants demonstrate enhanced physical properties, including rapid curing and reduced viscosity with high filler content, making them suitable for aerospace applications.
Implementation Method 1
reacting polythiols with these ethers and divinyl ethers
Data Source
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AI summary
Hydroxyl -containing bis(alkenyl) ethers can be incorporated into the backbone of polythioether prepolymers and can be used as curing agents in thiol -terminated polythioether prepolymer compositions. Cured sealants prepared using compositions containing hydroxyl - containing bis(alkenyl) ether-containing polythioether prepolymers and/or hydroxyl -containing bis(alkenyl) ether curing agents exhibit improved physical properties such as rapid curing and compatibility with fillers suitable for use in aerospace sealant applications.