Dual Cure Polythioether Sealant for Dark Zone Curing
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Solution Overview
Problem
Current sealant technologies face challenges in achieving rapid and efficient curing, especially in areas without direct light exposure, and often compromise on fuel resistance and glass transition temperature for such properties.
Innovation Solution
A dual cure polythioether composition comprising a dithiol monomer, diene monomer, radical cleaved photoinitiator, peroxide, and amine as a peroxide-amine redox initiator, which can be cured by actinic radiation and propagates a dark cure mechanism, allowing for rapid curing even in dark zones with excellent fuel resistance and low glass transition temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single cure mechanism (photocure or dark cure) is used, then the curing process is simple, but curing efficiency in dark zones is poor or fuel resistance is compromised
Solution Approach 1:
The patent combines photocure and dark cure mechanisms into a dual cure system. The composition includes both a photoinitiator for light-initiated curing and a peroxide-amine redox initiator for dark curing, allowing the sealant to cure effectively in both illuminated and dark zones while maintaining fuel resistance properties.
Solution Approach 2:
The patent uses a composite curing system with multiple initiator types (photoinitiator + peroxide-amine redox initiator) and multiple monomer components (dithiol + diene ± polythiol). This composite approach enables simultaneous achievement of rapid curing in dark zones and excellent fuel resistance that cannot be obtained with single-component systems.
2Speed
If photocure alone is used, then curing is rapid in light zones, but curing in dark zones is slow or incomplete
Solution Approach 1:
The patent segments the curing process into two independent mechanisms: photocure for light-exposed areas and dark cure for shadowed areas. This segmentation allows each mechanism to optimize its performance in its designated zone, with the peroxide-amine redox initiator specifically addressing dark zone curing that photocure cannot achieve.
Solution Approach 2:
The peroxide-amine redox initiator acts as an intermediary mechanism that bridges the gap left by photocure in dark zones. It provides an alternative curing pathway that does not require light activation, enabling complete curing throughout the sealant application including areas without direct light exposure.
3Reliability
If conventional sealants are used, then fuel resistance may be adequate, but curing time is long and dark zone conversion is poor
Solution Approach 1:
The patent changes the chemical parameters of the curing system by introducing a peroxide-amine redox initiator combination that enables rapid dark cure. This parameter change transforms the curing kinetics, achieving high conversion in dark zones within seconds to minutes rather than hours, while preserving fuel resistance through the polythioether polymer structure.
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 dual cure polythioether composition enables rapid curing within seconds, achieving 90% or greater conversion up to 5 cm into dark zones, combined with high jet fuel resistance and a glass transition temperature less than −50° C, suitable for applications like aircraft and automobile sealants.
Implementation Method 1
a radical cleaved photoinitiator... The composition may be cured by application of light from an actinic light source
Implementation Method 2
a peroxide; and an amine; where the peroxide and amine together are a peroxide-amine redox initiator
Data Source
AI summary
Compositions that are curable to polythioether polymers are provided, comprising: a) a dithiol monomer; b) a diene monomer; c) a radical cleaved photoinitiator; d) a peroxide; and e) an amine; where the peroxide and amine together are a peroxide-amine redox initiator. In some embodiments, the amine is a tertiary amine. In some embodiments, the amine is selected from the group consisting of dihydroxyethyl-p-toluidine, N,N-diisopropylethylamine, and N, N, N′, N″, N″-pentamethyl-diethylenetriamine. In some embodiments, the peroxide is selected from the group consisting of di-tert-butyl peroxide, methyl ethyl ketone peroxide, and benzoyl peroxide. In some embodiments, the composition may additionally comprise a polythiol monomer having three or more thiol groups.