Specialty Sealants

Specialized Formulations

Specialty Sealants

Specialty sealants cover chemistries built for demanding sealing applications that fall outside general-purpose epoxy, silicone, and polyurethane systems. This category currently centers on polysulfide sealants, high-performance elastomeric polymers used across aerospace, transportation, marine, and industrial environments, and will expand to include additional specialty chemistries over time.

Polysulfide sealants cure into durable, flexible rubber-like materials. Unlike rigid structural adhesives that transfer mechanical loads, they're designed to accommodate joint movement while maintaining long-term resistance to aviation fuels, hydraulic fluids, chemicals, moisture, UV exposure, and weathering. Their molecular backbone delivers durability without sacrificing elasticity, making them well suited to applications subject to vibration, thermal expansion, and pressure cycling.

From aircraft fuel tank sealing and fuselage assembly to structural glazing, expansion joints, and marine structures, polysulfide sealants provide environmental protection where long service life and chemical resistance are critical. Available in pourable, brushable, and non-sag formulations, they offer strong adhesion to metals, glass, composites, concrete, and many engineering substrates while maintaining a watertight, chemically resistant seal.

While polysulfide sealants provide strong adhesion and long-term environmental sealing, they are primarily designed to seal joints rather than carry structural loads. For high-strength permanent bonding of metals, composites, and engineering plastics, explore the dedicated Structural Epoxy Adhesives category.

Product selector guide

How to select the right polysulfide sealant?

For aerospace sealing applications, select polysulfide sealants based on application method, cure speed, and environmental requirements:

Class A: Low-viscosity brush-grade sealants for coating and surface sealing.
Class B: Extrusion-grade sealants for fillet sealing and gap filling applications.
Class C: Roller-grade sealants designed for large-area fuel tank sealing.
Rapid Cure: Selected when reduced processing time is required.
Non-Chromate: Preferred where environmental compliance requirements apply.

Polysulfide Sealants

Product	RTU Type	Application Area	Grade / Class	Application Method	Curing Mechanism	Color	Product Features	Specifications
WS-8010	Two-Part (2K)	Aircraft access doors, fillet sealing	Class B	Extrusion / Fillet	Chemical Cure at room temperature	Black / White	General purpose aerospace sealant with excellent adhesion and flexibility	AMS3284 Type 1 MIL-S-8784
WS-8020RC	Two-Part (2K)	Fuel tank sealing, general aerospace sealing	Class A	Brush Application	Rapid Chemical Cure at room temperature	Black	Rapid cure, high temperature resistance, fuel resistant	AMS8802 Type 2 AMS3276 Cessna CPN021 Type 1
WS-8020RC	Two-Part (2K)	Fuel tank sealing, structural sealing, high temperature applications	Class B	Extrusion / Gun Grade	Rapid Chemical Cure at room temperature	Black	Rapid curing fuel tank sealant with excellent environmental resistance	AMS3276 AMS8802 Type 2 Boeing BMS5-104 Type IV Boeing BMS3-32 Grade 2
WS-8030	Two-Part (2K)	Lightweight fuel tank sealing	Class B	Extrusion	Chemical cure at room temperature	White / Gray	Lightweight formulation with high temperature resistance	AMS3281 Type 1
WS-8031	Two-Part (2K)	Lightweight aircraft fuel tank sealing	Class B	Extrusion	Chemical Cure at room temperature	White	Lightweight sealant designed for aerospace fuel systems	AMS3281 Type 3
WS-8032	Two-Part (2K)	Fuel tank sealing and aerospace structures	Class B	Extrusion	Chemical Cure at room temperature	White	Lightweight fuel tank sealant with aerospace qualification	AMS3281 Type 2 Korea Aerospace Industries A84MS0022
WS-8032	Two-Part (2K)	Fuel tank sealing, roller application	Class C	Roller Grade	Chemical Cure at room temperature	White	Low viscosity roller grade sealant for large surface application	AMS3281 Type 2 Korea Aerospace Industries A84MS0022
WS-8032S	Two-Part (2K)	Fuel tank sealing, non-chromate applications	Class B	Extrusion	Rapid Chemical Cure at room temperature	White	Lightweight, rapid cure, environmentally friendly non-chromate formulation	Bombardier BAMS552-009 Airbus A2MS552-008
WS-8032S	Two-Part (2K)	Fuel tank and environmental sealing	Class C	Roller Grade	Chemical Cure at room temperature	White	Non-chromate roller grade sealant for aerospace applications	Bombardier BAMS552-009 Airbus A2MS552-008
WS-8033	Two-Part (2K)	Lightweight fuel tank sealing	Class B	Extrusion	Chemical Cure at room temperature	White	Lightweight aerospace fuel tank sealant	Embraer MEP09-084 Grade B Type 1
WS-8035	Two-Part (2K)	Fuel tank sealing	Class A	Brush Grade	Rapid Chemical Cure at room temperature	Black	Fast curing brushable fuel tank sealant	Boeing BMS5-184
WS-8035	Two-Part (2K)	Fuel tank sealing and general aerospace sealing	Class B	Extrusion	Rapid Chemical Cure at room temperature	Black	Rapid cure, general purpose aerospace sealant	Boeing BMS5-184
WS-8070	Two-Part (2K)	Corrosion protection sealing	Class B	Extrusion	Chemical Cure at room temperature	Gray	Corrosion-inhibitive aerospace sealant	MIL-PRF-81733 Class 1 Grade A Type II Cessna CPN007 Type X
WS-8072	Two-Part (2K)	Corrosion protection and environmental sealing	Class B	Extrusion	Rapid Chemical Cure at room temperature	Gray	Non-chromate, lightweight corrosion inhibitive sealant	MIL-PRF-81733 Class 1 Grade B Type II AMS3265

Frequently asked questions

Frequently Asked Questions about Polysulfide Sealants

What is polysulfide sealant used for?

Polysulfide sealants are used in applications requiring strong chemical resistance, fuel resistance, flexibility, and long-term sealing reliability. They are commonly used for aircraft fuel tank sealing, aerospace structures, marine applications, insulating glass units, expansion joints, automotive sealing, and industrial assemblies exposed to oils, solvents, and harsh environmental conditions.

Is polysulfide better than silicone?

Neither technology is universally better; the right choice depends on the application requirements. Polysulfide sealants generally offer stronger resistance to fuels, oils, solvents, and gases, making them a common choice for aerospace and chemical-exposure applications. Silicone sealants generally offer better UV resistance, wider temperature capability, and stronger long-term weathering performance, making them a common choice for outdoor glazing and high-temperature sealing.

How long does polysulfide sealant last?

A properly selected and applied polysulfide sealant can provide an extended service life, supported by strong resistance to moisture, chemicals, fuel exposure, and temperature cycling that helps it maintain flexibility and sealing performance over time. Actual service life depends on the formulation, substrate compatibility, joint design, environmental exposure, and application conditions, so specific service life expectations should be confirmed against product-specific data.

Can polysulfide withstand aviation fuel?

Yes. Polysulfide sealants are widely recognized for their resistance to aviation fuels, including jet fuel and other hydrocarbon-based fluids. This fuel-resistant property makes polysulfide one of the preferred sealing technologies for aircraft fuel tanks, fuel system components, and aerospace structures where long-term resistance to aggressive chemicals is required.

How does polysulfide sealant cure?

Polysulfide sealants cure through a chemical crosslinking reaction, where the liquid polysulfide polymer reacts with a curing agent to form a flexible, three-dimensional elastomer network. Two-component systems begin curing immediately after mixing, while one-component formulations cure through exposure to environmental conditions, depending on the specific chemistry.

What is the difference between gun grade and pourable polysulfide sealants?

Gun grade polysulfide sealants are higher-viscosity, non-sag formulations designed for vertical, overhead, and controlled bead applications using dispensing equipment. Pourable polysulfide sealants have lower viscosity and are self-leveling, making them suited to horizontal joints, expansion gaps, and large-area sealing applications where complete cavity filling is required.

Are polysulfide sealants waterproof?

Yes. Once fully cured, polysulfide sealants offer strong resistance against water penetration and moisture exposure. Their low permeability and flexible, rubber-like structure help them maintain a reliable seal through weathering, thermal cycling, and prolonged outdoor exposure.

Learn more

Understanding Polysulfide Sealants

Sealant technology engineered for strong chemical resistance, fuel resistance, and long-term environmental durability

Chemical Resistant

Synthetic Elastomer

What Are Polysulfide Sealants?

Polysulfide sealants are elastomeric sealing materials based on a liquid polysulfide polymer backbone. They are engineered for applications requiring strong resistance against fuels, solvents, chemicals, moisture, and harsh environmental exposure.

Unlike silicone or polyurethane sealants, which rely on siloxane or urethane chemistry, polysulfides contain repeating sulfur-containing polymer chains that provide low gas permeability and strong resistance to hydrocarbon-based fluids.

During cure, reactive terminal groups crosslink the liquid polymer into a flexible three-dimensional elastomer network, forming a durable seal.

Polysulfide Technology – Key Characteristics

Strong Chemical Resistance

Strong resistance to aviation fuels, oils, solvents, hydraulic fluids, and aggressive chemicals.

Low Gas & Moisture Permeability

The sulfur-based polymer structure provides strong barrier properties against water vapor and gases.

Long-Term Flexibility

Maintains elasticity under temperature cycling, vibration, and continuous mechanical movement.

Types of Polysulfide Sealants

Different formulations provide different processing methods, cure profiles, and application performance

Single Component 1K

1. One-Component (1K) Polysulfide Sealants

One-component polysulfide sealants are pre-formulated systems supplied ready for application. They cure through exposure to atmospheric moisture or oxygen, depending on the specific formulation chemistry.

These systems offer convenience for field applications where mixing equipment is impractical.

Mixed Cure 2K

2. Two-Component (2K) Polysulfide Sealants

Two-component polysulfide sealants consist of a base polymer component and a curing agent that are mixed immediately before application.

The chemical reaction creates a highly crosslinked elastomer with strong mechanical properties, chemical resistance, and long-term durability.

Polysulfide Sealant Application Formats

Thixotropic Gun Grade

3. Gun Grade Polysulfide Sealants

Gun grade polysulfides are formulated with higher viscosity and controlled flow characteristics, allowing application through manual or pneumatic dispensing equipment.

The non-sag formulation allows the sealant to hold position on vertical and overhead surfaces while forming a durable elastic seal.

Typical Uses:

Aircraft fuel tank sealing, construction joints, automotive sealing, marine assemblies.

Self-Leveling Pourable

4. Pourable Grade Polysulfide Sealants

Pourable polysulfides have lower viscosity and are designed to flow freely into horizontal joints, gaps, and cavities before curing into a flexible rubber seal.

They offer good movement capability and are commonly selected for large-area sealing applications requiring uniform filling.

Typical Uses:

Airport runway joints, expansion joints, insulating glass units, and large structural gaps.

Polysulfide Curing Mechanism

The transformation from liquid polymer chains into a durable elastomeric sealing network

Stage 1

Liquid Polymer Before Cure

The polysulfide polymer exists as a flexible liquid chain containing reactive terminal groups. At this stage, the material remains flowable and can wet the substrate surface.

Stage 2

Crosslinking Reaction

The curing agent reacts with terminal functional groups, connecting individual polymer chains into a growing three-dimensional network.

Stage 3

Fully Cured Elastomer

The completed crosslinked rubber structure provides flexibility, chemical resistance, low permeability, and long-term sealing performance.

Key Performance Benefits

Why polysulfide sealants are a common choice for demanding sealing environments

1. Fuel & Chemical Resistance

Hydrocarbon Resistance: The sulfur-containing polymer structure provides strong resistance against aviation fuels, diesel, gasoline, hydraulic fluids, and lubricants.

Chemical Stability: Maintains sealing integrity when exposed to solvents, oils, cleaning agents, and industrial chemicals.

2. Environmental Durability

Weather Resistance: Strong resistance against UV exposure, ozone, humidity, and temperature cycling.

Extended Service Life: Formulated to maintain elasticity and sealing performance over long operating periods in demanding outdoor environments; actual service life depends on formulation, substrate, joint design, and exposure conditions.

3. Movement Capability

Elastic Recovery: The flexible polymer network allows repeated expansion and contraction without cracking.

Stress Absorption: Accommodates thermal expansion differences between dissimilar substrates.

4. Low Gas & Moisture Permeability

Barrier Protection: The dense sulfur-based polymer structure minimizes gas transmission and moisture penetration, which is why polysulfides are a common choice for fuel tanks, aerospace sealing, and insulating glass applications.

Core Industrial Applications

Polysulfide sealants are selected where long-term sealing reliability and chemical resistance are critical

Industry	Application
Aerospace & Aviation	Aircraft fuel tank sealing, fuselage joints, access panels, and aerospace structures requiring resistance to aviation fuels and hydraulic fluids.
Automotive & Transportation	Fuel system sealing, vehicle body joints, industrial equipment sealing, and applications exposed to oils and chemicals.
Marine & Shipbuilding	Deck joints, marine structures, underwater sealing, and applications requiring saltwater and weather resistance.
Construction	Expansion joints, concrete sealing, building facades, and structural gaps exposed to movement.
Insulating Glass	Secondary seal applications requiring low moisture and gas permeability.

Polysulfide vs Other Sealant Technologies

General positioning across three common sealant chemistries. Actual performance varies by specific formulation and test conditions, so product-specific data should be checked before final selection.

Property	Polysulfide	Silicone	Polyurethane
Fuel Resistance	Strong	Limited	Moderate
UV Resistance	Good	Strong	Good
Gas Permeability	Strong barrier	Moderate	Moderate