Polyurea Sealant Fuel Resistance via Composite Network
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Solution Overview
Problem
Aerospace sealant compositions face challenges in achieving both fuel resistance and water resistance while maintaining improved tensile strength and elongation, with existing sealants often compromising on these properties.
Innovation Solution
The development of polyurea compositions comprising a polyformal-isocyanate prepolymer and a polythioether-isocyanate prepolymer, using specific reaction products of polyformal polyols and polythioether polyols with diisocyanates and an amine curing agent, to create a sealant with enhanced properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If difunctional polythioethers are used in sealant compositions, then low temperature flexibility and fuel resistance are improved, but the sealant swells upon prolonged exposure to hydrocarbon fuel and lubricants
Solution Approach 1:
The patent combines polythioether polyol (providing fuel resistance and low-temperature flexibility) with polyformal polyol (providing dimensional stability and water resistance) and reacts both with isocyanate to form a composite polymer network. This composite structure achieves simultaneous fuel resistance, dimensional stability, and water resistance that individual components cannot provide alone.
2Reliability
If polyfunctional polythioethers are used to improve fuel resistance and hardness, then fuel resistance and flexibility are improved, but elongation is compromised
Solution Approach 1:
The patent uses difunctional polythioether polyol (not polyfunctional) to provide localized fuel resistance and flexibility properties where needed, while the polyformal polyol component provides the elongation and tensile strength. This local quality approach allows each component to contribute its optimal properties without the negative effects of polyfunctional crosslinking.
3Reliability
If existing sealant compositions are used, then fuel resistance is achieved, but water resistance and tensile strength are compromised
Solution Approach 1:
The patent creates a composite polymer network from polythioether-isocyanate prepolymer and polyformal-isocyanate prepolymer, where the polythioether component provides fuel resistance and the polyformal component provides water resistance and enhanced tensile strength. The synergistic combination achieves all three properties simultaneously.
4Reliability
If sealant compositions prioritize fuel resistance, then fuel resistance is improved, but water resistance is compromised
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating polyformal polyol (a water-resistant component) alongside polythioether polyol (fuel-resistant). This parameter change in the polymer composition enables simultaneous resistance to both fuel and water that single-component systems cannot achieve.
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 sealant exhibits improved tensile strength, elongation, and resistance to both fuel and water, making it suitable for aerospace applications with enhanced performance.
Implementation Method 1
a polyformal-isocyanate prepolymer comprising the reaction products of reactants comprising a polyformal polyol and a first diisocyanate; a polythioether-isocyanate prepolymer comprising the reaction products of reactants comprising a polythioether polyol and a second diisocyanate
Implementation Method 2
a curing agent comprising an amine
Data Source
Figure 1
AI summary
Disclosed are polyurea compositions comprising the reaction products of a polyformal-isocyanate prepolymer and a curing agent comprising an amine. The compositions are useful as sealants in aerospace applications.