What Is Polysulfide Sealant?

2026-06-22

Polysulfide sealant is formulated using liquid polysulfide rubber with mercaptan-terminated chains as the base material, combined with curing agents, additives, and fillers. During application, a cross-linked network is formed through the reaction between the liquid polysulfide rubber and the curing agent. Polysulfide sealants exhibit excellent resistance to air, jet fuel, fuel vapors, water vapor, non-polar liquid media, and atmospheric conditions. They consistently maintain reliable adhesion to surfaces such as aluminum alloys, structural steel, titanium alloys, polyurethane primers, epoxy primers, resin-based composites, cement, and glass, while maintaining certain tensile mechanical properties. It can flex without cracking at -55°C, ensures structural sealing under dynamic conditions, and maintains structural sealing long-term at 120°C. The most distinctive feature of polysulfide sealants is the presence of disulfide bonds in their molecular chains, which provide excellent resistance to nonpolar media such as fuel. They also have low vapor permeability. These sealants are primarily used for bonding and sealing various components in the construction industry, in the manufacture of insulated glass units, and for specialized military applications such as integral aircraft fuel tanks, fuel compartments, and anti-corrosion sealing of aircraft fuselages.

Types and Typical Formulations of Polysulfide Sealants

Based on their packaging, polysulfide sealants can be classified into single-component, two-component, and multi-component types; based on their terminal groups, they can be classified into mercaptan-terminated, epoxy-terminated, and silane-terminated polysulfide sealants, among others.

One-Component Polysulfide Sealants

Single-component polysulfide sealants generally rely on moisture in the air as a curing accelerator.

Formula No.	Component Name	Parts by Mass
1	Silane-mercapto terminated polysulfide polymer synthesized from LP2 and trimethylchlorosilane (CH3)3SiCl	100
	Lead Dioxide	7
	Calcium Carbonate	120
	Chlorinated Paraffin	97
2	Silane-mercapto terminated polysulfide polymer synthesized from LP2 and trimethylchlorosilane ((CH₃)₃SiCl)	100
	Manganese Dioxide	15
	Calcium Carbonate	120
	Chlorinated Paraffin	45
	Dibutyl Phthalate	45

Two-Component Polysulfide Sealants

Two-component polysulfide sealants generally consist of two components: a base paste and a curing paste. The base paste contains liquid polysulfide rubber, reinforcing agents, tackifiers, plasticizers, and other ingredients, while the curing paste contains curing agents, plasticizers, accelerators, curing inhibitors, and other ingredients.

Component Group	Ingredient Name	Parts by Mass
Base Compound	Liquid Polysulfide Rubber G1	50
	Liquid Polysulfide Rubber G131	50
	Carbon Black	30
	Calcium Carbonate	10
	Titanium Dioxide	10
	Silane Coupling Agent	1
	Stearic Acid	1
Curing Paste	Manganese Dioxide	100
	Dibutyl Phthalate	120
	Calcium Carbonate	20
	Diphenylguanidine	8
	Stearic Acid	1

Multi-Component Polysulfide Sealants

To improve the storage stability of polysulfide sealants, in multi-component polysulfide sealants—unlike two-component polysulfide sealants—the tackifier and accelerator are each formulated as separate components. Specifically, the tackifier in the base paste and the accelerator in the curing paste are each formulated as a separate component and are thoroughly mixed together before use. The shelf life of two-component polysulfide sealants is generally 6 months, while that of multi-component polysulfide sealants is typically 9 months or longer. Due to the large number of components in multi-component polysulfide sealants—particularly the relatively small proportion of the accelerator—they are not suitable for manual mixing in the field and generally require the use of a three-roll mill.