Dimercaptan Polythioether Polymers for Aerospace Sealant Pot Life
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Solution Overview
Problem
Aerospace sealants require a combination of long application time (pot life) and short curing time, along with high temperature resistance, which is difficult to achieve with existing polymeric materials that are liquid at room temperature and have low glass transition temperature (Tg) and good fuel resistance.
Innovation Solution
Development of dimercaptan terminated polythioether polymers with specific molecular structures and blends with polysulfides, which are liquid at room temperature, have low Tg, and exhibit excellent fuel resistance, along with the use of reactive diluents to reduce viscosity and extend pot life without solvents, and inclusion of curing agents and additives for controlled curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If conventional polymeric materials are used to achieve low Tg and liquid state at room temperature, then good fuel resistance and low temperature flexibility are obtained, but pot life is extended while curing time increases
Solution Approach 1:
The patent modifies the chemical structure of polythioether polymers by introducing specific side chains (formula II) with adjustable parameters (a, b, c) and terminal functional groups (R2), enabling independent optimization of pot life and curing time without compromising low Tg or fuel resistance
Solution Approach 2:
The invention creates composite polymer systems combining polythioether base polymers with specific side chains and terminal functional groups, achieving synergistic effects that provide both extended pot life and accelerated curing while maintaining low temperature flexibility and fuel resistance
2Reliability
If polysulfide polymers are used to achieve fuel resistance, then good fuel resistance is obtained, but viscosity is high and pot life is reduced
Solution Approach 1:
The patent introduces alkyl side chains at specific positions on the polythioether backbone, creating local regions of reduced polarity and increased free volume that lower overall viscosity while maintaining fuel resistance through the sulfur-containing backbone structure
Solution Approach 2:
The invention adjusts the length and branching of alkyl side chains (parameters a, b, c in formula II) to optimize the balance between viscosity reduction and fuel resistance maintenance, allowing independent tuning of these properties
3Ease of operation
If reactive diluents are added to reduce viscosity, then viscosity is reduced and handling is improved, but pot life is extended excessively and curing requirements become more complex
Solution Approach 1:
The patent incorporates terminal functional groups (R2) directly into the polymer structure that serve as built-in reactive sites, eliminating the need for separate reactive diluents and simplifying the curing system while maintaining improved handling properties
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 polymers provide improved low temperature flexibility, fuel resistance, and controlled curing characteristics, enabling effective sealing in aerospace applications with reduced solvent use and improved handling properties.
Implementation Method 1
have low Tg, are liquid at room temperature
Implementation Method 2
fuel resistant nature upon crosslinking
Implementation Method 3
upon crosslinking
Data Source
AI summary
Dimercaptan terminated polythioether polymers are disclosed, as are methods for making and using the same.