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 achieve strong adhesion with 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 coating is formed from a reaction product of polyepoxide, sulfur-functional azole, and phosphorous acid, and the sealant is deposited from a composition including a polysulfide polymer, enhancing 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 modification provides functional groups that enhance bonding to both the primer coating and the substrate, while maintaining the fuel-resistant properties of the polysulfide backbone. This resolves the adhesion problem while preserving fuel resistance.
Solution Approach 2:
The patent modifies the chemical parameters of the polysulfide polymer by introducing silane functional groups and controlling the molecular weight and composition. These parameter changes enable the sealant to achieve both good adhesion to the primer coating and maintained fuel resistance, resolving the contradiction between these two properties.
2Reliability
If polysulfide sealant is applied to aluminum substrate with primer coating, then fuel resistance is improved, but interlayer adhesion deteriorates
Solution Approach 1:
The patent creates a composite sealant system combining silane-modified polysulfide polymer with specific additives and modifiers. This composite material integrates the fuel-resistant properties of polysulfide with the adhesion-enhancing capabilities of silane functional groups, achieving both improved interlayer adhesion and maintained fuel resistance simultaneously.
Solution Approach 2:
The patent optimizes the molecular weight, functional group content, and composition ratios of the silane-modified polysulfide to achieve the desired balance between adhesion and fuel resistance. By carefully controlling these parameters, the sealant achieves strong interlayer adhesion while maintaining excellent fuel-resistant 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 system achieves strong interlayer adhesion and substrate adhesion, with a cured sealant showing less than 40% volume swell in jet reference fluid after immersion, effectively blocking fuel and gases, and demonstrating excellent peel strength and cohesive properties.
Implementation Method 1
methods of electrocoating an electrically conductive substrate serving as an anode in an electrical circuit comprising the anode and a cathode that are immersed in an aqueous resinous dispersion comprising passing electric current between the anode and the cathode to cause a resinous composition to deposit on the anode
Implementation Method 2
sulfur-containing polymers, such as polysulfides, which are polymers that have disulfide (-S-S-) linkages
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.