Silane-Modified Polysulfide Sealant Adhesion to Epoxy Primer
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Solution Overview
Problem
Aerospace sealants with sulfur-containing polymers, such as polysulfides, often fail to adhere well to corrosion-resistant primer coatings and substrates like aluminum, leading to inadequate fuel resistance and durability in aerospace applications.
Innovation Solution
A coating/sealant system comprising a phosphated epoxy resin coating and a sulfur-containing polysulfide sealant, where the polysulfide sealant is deposited over the coating, formed from a reaction product of polyepoxide, sulfur-functional azole, and phosphorous acid, providing improved adhesion and fuel resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sulfur-containing polymers (polysulfides) are used in aerospace sealant compositions, then fuel resistance is improved, but adhesion to primer coating and substrate deteriorates
Solution Approach 1:
The patent introduces a silane-modified polysulfide polymer as an intermediary material that bridges the gap between the primer coating and the sealant. The silane groups in the polymer provide bonding capability to the primer coating while the polysulfide backbone maintains fuel resistance, thus resolving the adhesion problem without sacrificing fuel resistance
Solution Approach 2:
The patent modifies the chemical structure of the polysulfide polymer by incorporating silane groups, which changes the surface properties and chemical reactivity of the material. This parameter change enables the polymer to form strong bonds with the primer coating while maintaining its fuel-resistant properties
2Reliability
If polysulfide sealant is applied over primer coating, then fuel resistance is achieved, but interlayer adhesion between sealant and coating is insufficient
Solution Approach 1:
The patent creates a composite material system consisting of silane-modified polysulfide polymer combined with specific curing agents. This composite structure integrates the fuel resistance of polysulfides with the adhesion properties of silane-modified polymers, achieving both required properties simultaneously
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 system achieves excellent interlayer adhesion and substrate adhesion, with a high peel strength and low volume swell after immersion in jet reference fluid, ensuring effective fuel resistance and durability in aerospace environments.
Implementation Method 1
adding a sulfur-functional azole to a composition comprising a phosphated epoxy resin derived from at least (i) a polyepoxide
Implementation Method 2
adding a base to the composition after at least a portion of the sulfur-functional azole has been added
Implementation Method 3
passing electric current between the anode and the cathode to cause a resinous composition to deposit on the anode
Data Source
AI summary
A coating/sealant system that includes a coating and a sealant deposited over at least a portion of the coating, in which the coating includes a reaction product formed from reactants comprising a phosphated epoxy resin and a curing agent, and the sealant includes a sulfur-containing polymer.