Silicones Sealant

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Industrial Silicone Sealants

Silicone sealants are a reference sealing technology for industrial applications requiring flexibility, durability and resistance across a broad temperature range. They can bond or seal metals, glass, engineering plastics and composites, while maintaining long-term elasticity and resistance to UV exposure, moisture and many environmental stresses.

Samaro distributes the DOWSIL™ and XIAMETER™ ranges from Dow for industrial silicone sealing applications.

What is the difference between silicone and silicone sealant?

Silicone refers to the base polymer chemistry, typically PDMS — polydimethylsiloxane — used to formulate many types of products including fluids, greases, resins and elastomers.

A silicone sealant is a formulated product, generally supplied in a cartridge or tube, designed for sealing and flexible bonding applications. Many one-component silicone sealants cure at room temperature in the presence of atmospheric moisture and form a permanently flexible joint.

The distinction between a silicone sealant and a silicone adhesive mainly depends on the required level of adhesion and mechanical performance: some formulations are specifically designed for bonding, while others are primarily intended for sealing.

What types of industrial silicone sealants are available?

The DOWSIL™ and XIAMETER™ ranges cover several families of industrial silicone sealants, each suited to different chemical and application requirements.

Acetoxy-cure silicone sealants

DOWSIL™ 732 and DOWSIL™ AP are multipurpose acetoxy-cure silicone sealants.

This type of silicone releases acetic acid during curing, producing the characteristic vinegar-like odour. It generally provides good adhesion to many non-porous substrates such as glass, glazed ceramics and aluminium.

DOWSIL™ 732 is listed with FDA, NSF 51, NSF 61 and MIL-A-46106 certifications on the current Samaro product page. Its service temperature range extends from approximately -65°C to +180°C, depending on the grade.

DOWSIL™ AP is a multipurpose acetoxy-cure silicone sealant with high flexibility and a service temperature range of approximately -50°C to +180°C.

Neutral-cure silicone sealants

Neutral-cure silicone sealants are preferred when corrosion-sensitive materials or electronic assemblies need to be protected from acidic curing by-products.

Products such as DOWSIL™ 7091 and DOWSIL™ 3145 are neutral-cure silicone solutions used for flexible bonding and sealing applications.

DOWSIL™ 7091 combines flexibility, broad substrate adhesion and room-temperature curing, making it suitable for applications in transportation, marine, electronics and general industry.

DOWSIL™ 3145 is a one-component neutral silicone adhesive and sealant offering high mechanical strength and room-temperature curing, particularly for demanding electronic and industrial applications.

Silicone sealants for demanding thermal or chemical environments

Some DOWSIL™ silicone sealants are specifically formulated for applications exposed to demanding temperatures or aggressive chemical environments.

DOWSIL™ 730 FS is a one-component acetoxy-cure fluorosilicone sealant developed for applications requiring resistance to hydrocarbons, solvents and aggressive chemicals.

Other high-temperature silicone grades can be selected according to the temperature profile and specific application requirements.

Two-component silicone sealants and primers

Two-component silicone sealants cure by mixing a base and curing component rather than relying solely on atmospheric moisture.

They can be particularly useful for industrial processes requiring controlled curing or for larger bonding and sealing areas.

DOWSIL™ primers can also be used to improve adhesion on certain difficult substrates. The need for a primer should always be assessed according to the substrate, surface preparation and silicone formulation.

When selecting a silicone sealant, I do not look only at its temperature resistance. The substrates, joint movement, exposure to moisture, UV or chemicals, curing mechanism and dispensing process all need to be considered. Acetoxy, neutral, fluorosilicone and two-component technologies do not respond to the same constraints. Our role is to identify the appropriate technology and determine whether a primer or specific certification also needs to be considered.

Thomas Brunet

Adhesives Brand Manager at Samaro

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What are industrial silicone sealants used for?

Industrial silicone sealants are used wherever durable sealing, flexibility and resistance to environmental stresses are required.

Appliances and lighting: sealing ovens, lamps, cooking equipment and luminaires.
Automotive and transportation: glazing joints, body sealing, housings and connector protection.
Food-processing equipment: sealing tanks, mixers and processing equipment using products with the appropriate certifications.
Aerospace and marine: window and porthole sealing, external joints and protection against environmental exposure.
Electronics: sealing housings and components where flexibility and environmental protection are required.
Nuclear: specific silicone grades may be available in PMUC versions for applications requiring this qualification.

What are the limitations of silicone sealants?

Silicone sealants have several characteristics that need to be considered during selection.

They are generally difficult to paint once cured, are not intended to replace structural adhesives for highly loaded assemblies, and may require a primer on difficult-to-bond substrates.

Acetoxy-cure silicone sealants can also be unsuitable for corrosion-sensitive metals or electronic assemblies because they release acetic acid during curing. In these cases, a neutral-cure formulation should be considered.

DOWSIL™ solutions available from Samaro

DOWSIL™ 732: multipurpose acetoxy-cure silicone sealant for industrial sealing and flexible bonding applications. The current Samaro product page lists FDA, NSF 51, NSF 61 and MIL-A-46106 certifications.
DOWSIL™ AP: multipurpose acetoxy-cure silicone sealant offering high flexibility and good adhesion to many non-porous substrates.
DOWSIL™ 730 FS: solvent- and chemical-resistant fluorosilicone sealant for demanding industrial environments.
DOWSIL™ 3145: neutral-cure silicone for bonding, protection and sealing of electronic and industrial components.
DOWSIL™ 7091: high-performance neutral-cure silicone adhesive and sealant for flexible bonding and sealing applications.

Explore our pages dedicated to two-component silicone sealants, silicone adhesives and sealants and solutions for Electric & Electronic Protection & Assembly.

Our technical team can help you select a silicone solution suited to your application.

How do you choose an industrial silicone sealant?

The choice depends on the substrates, service temperature, joint movement and exposure to moisture, UV or chemicals. The curing mechanism and any certification requirements should also be considered.

When should you use a primer with a silicone sealant?

A primer may be required when the silicone does not provide sufficient adhesion to the substrate on its own. Its use depends on the material, surface condition and silicone formulation, so compatibility should be checked for each assembly.

How does a silicone joint accommodate movement and thermal expansion?

Once cured, silicone remains flexible and can accommodate relative movement between assembled parts. The actual movement capability depends on the formulation, joint geometry and mechanical stresses involved.

Can silicone sealant be applied to plastics or painted surfaces?

Some silicone sealants can bond to plastics or coated surfaces, but adhesion varies significantly depending on the material and surface treatment. Adhesion testing and, where appropriate, a suitable primer should be considered before validating the process.

How do you check whether a silicone sealant is suitable for a regulated application?

Check the certifications and specifications associated with the exact product grade and the conditions under which they apply. Food-processing, aerospace, railway or nuclear applications may require different approvals, so the current technical data sheet and certificates should always be reviewed before validation.

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