Amine-Hydroxy Capped Polythioethers for Aviation Sealants
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Solution Overview
Problem
Current epoxy-terminated polysulfides used in aviation and aerospace applications are toxic due to the use of epichlorohydrin, produce corrosive byproducts, and have high viscosity and broad epoxy equivalent weight ranges, which are not environmentally compatible and do not meet the requirements for flexibility, fuel resistance, and high-temperature resistance.
Innovation Solution
The development of amine/hydroxy-capped polythioethers synthesized without epichlorohydrin, using a reaction between dithiols and monoepoxides, which results in a controlled and narrow epoxy equivalent weight range, and are formed without generating hydrolysable chlorine, providing flexibility, fuel resistance, and high-temperature resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If epichlorohydrin is used as a reactant to synthesize epoxy-terminated polysulfides, then fuel resistance and flexibility are improved, but toxicity and corrosive byproduct generation increase
Solution Approach 1:
The patent removes epichlorohydrin from the reaction system and replaces it with alternative reactants (glycidyl ether and dithiol). This extraction of the harmful substance eliminates the generation of hydrolysable chlorine byproducts while maintaining the desired fuel resistance and flexibility properties through the polythioether backbone structure.
Solution Approach 2:
The patent converts the harmful epichlorohydrin-based synthesis route into a beneficial alternative by using glycidyl ether and dithiol reactants. The new synthesis method not only eliminates toxicity and corrosive byproducts but also provides additional benefits including lower viscosity and controlled epoxy equivalent weight, transforming a harmful process into a superior manufacturing approach.
2Reliability
If epichlorohydrin is used as a reactant, then fuel resistance is improved, but corrosive hydrolysable chlorine byproducts are generated
Solution Approach 1:
The patent extracts and removes the chlorine-containing epichlorohydrin reactant from the synthesis system, replacing it with chlorine-free alternatives. This elimination prevents the formation of hydrolysable chlorine byproducts while preserving the fuel resistance property through the sulfur-containing polythioether backbone that provides excellent chemical stability.
3Reliability
If epoxy-terminated polysulfides are synthesized using conventional methods, then fuel resistance is achieved, but viscosity is high and epoxy equivalent weight range is broad
Solution Approach 1:
The patent changes the molecular parameters by using specific reactant ratios and alternative chemistry (glycidyl ether plus dithiol) to produce polythioethers with controlled epoxy equivalent weights in the range of 200-1000 g/eq. This parameter optimization results in lower viscosity compared to conventional epoxy-terminated polysulfides, improving ease of manufacture and application while maintaining fuel resistance.
4Manufacturing precision
If thorough washing is performed to remove unreacted epichlorohydrin, then purity is improved, but processing time and complexity increase
Solution Approach 1:
The patent removes the need for extensive washing operations by eliminating epichlorohydrin from the reaction system entirely. The alternative synthesis using glycidyl ether and dithiol produces a cleaner reaction mixture with fewer byproducts and unreacted starting materials, significantly reducing or eliminating the need for thorough washing steps while achieving high purity product.
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 epoxy-capped polythioethers exhibit improved properties such as low viscosity, controlled epoxy equivalent weight, and excellent chemical resistance, including resistance to aviation and aerospace fuels, while being environmentally friendly and compatible with other epoxy compounds.
Implementation Method 1
formed by the addition of thiol across the double bond of a monoepoxide comprising an olefinic group
Data Source
AI summary
Epoxy-capped polythioethers, amine/hydroxy-capped polythioethers, and curable compositions of epoxy-capped polythioethers are disclosed.