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Sealant in use

What is a Sealant and Why Does It Matter?

Posted 25 Jun 2020 by Johanna Sieber - Product Manager EMEA Engineering Adhesives, Marketing Manager, Paper Converting

Sealants might not be the most visible part of a product or structure, but they play a critical role in how many different products perform, last, and look. Whether you are building a skyscraper or assembling a household appliance, the right sealant can make all the difference.

Let’s take a closer look at what sealants are, how they work, and why they are essential in so many industries.

What Exactly Is a Sealant?

A sealant is typically a paste-like material applied between two surfaces to fill gaps and form a barrier. It adheres to both sides of a joint and can remain flexible or cure into an elastic state, depending on the formulation and application. They either retain their plasticity after being introduced into the joint or change to a more or less elastic state through a mostly chemical reaction.

The primary role of a sealant is to close off gaps between materials, preventing unwanted substances like air, water and other fluids, dust, or chemicals from passing through. In many cases, sealants eliminate the need for mechanical solutions like welding or soldering. Unlike adhesives, which are primarily designed for bonding two substrates, sealants are designed to provide flexible, gap-filling and environmental protection. However, there are some sealant formulations that can serve both purposes and also act as adhesives.

For example, silicone sealants are valued for their high flexibility and weather resistance in building applications. Polyurethane sealants, on the other hand, offer excellent adhesion and abrasion resistance in automotive and industrial settings.

Where Are Sealants Used?

Sealants are everywhere. From construction to transportation, household appliances to medical devices, sealants help maintain integrity, improve efficiency, and enhance durability.

Common applications include:

It’s hard to imagine modern manufacturing without them.

Why Are Sealants Important?

While the primary job of a sealant is to fill and protect joints, modern formulations often do more than just seal. They also offer added benefits depending on the specific needs of the application.

Main Functions:

  • Sealing joints and gaps
  • Blocking out water, air, dust, and other media
  • Allowing for controlled movement between materials

Additional Benefits:

  • Dampening sound and vibration – especially in transportation and electronics.
  • Protecting against corrosion – particularly in metal joints or maritime equipment.
  • Supporting fire resistance – intumescent sealants expand when heated to block flames.
  • Adding visual or design appeal – with color-matched or invisible seal lines in consumer-facing products.
  • Acting as electrical insulators or conductors – critical in EV batteries and circuit assemblies.
  • Inhibiting mold or microbial growth – ideal for HVAC, food processing, and medical environments.
  • Functioning as an elastic adhesive – allowing dynamic joints to stay bonded under stress.

These secondary benefits often become just as important as sealant itself, especially in high-performance and highly-regulated environments.

Choosing the Right Sealant

Selecting the right sealant depends on your materials, the environmental conditions, and the demands of the application. That’s why it’s important to work with a partner who understands both the chemistry of the sealant and the industry where the sealant is being applied.

At H.B. Fuller, we develop sealant technologies tailored to diverse markets, from construction and transportation to electronics and renewable energy. Our solutions are designed to meet the performance, sustainability, and durability requirements that modern products demand.

We take into account a number of different considerations when designing our sealants for our customers, including:

  • Substrate compatibility:
    • Not all sealants adhere equally well to all surfaces. It's crucial to choose a formulation that bonds effectively with your materials, whether it's metal, plastic, glass, concrete, or composite. Compatibility affects not just initial adhesion, but long-term performance, especially under dynamic stresses.
  • Thermal expansion and contraction
    • Materials expand and contract with temperature changes. The sealant must accommodate this movement without cracking, detaching, or degrading. For applications exposed to wide temperature swings, like building facades or vehicle exteriors, flexibility and elongation are key.
  • Chemical exposure
    • Environments with exposure to oils, fuels, solvents, cleaning agents, or harsh weather require chemically resistant sealants. For example, sealants used in fuel tanks or industrial machinery need to withstand corrosive or reactive substances without breaking down.
  • Application method (manual, automated, etc.)
    • Some sealants are better suited to manual application with caulking guns, while others are optimized for high-speed, automated dispensing in factory settings. Factors like viscosity, open time (workability), and cure rate will affect how easily the sealant integrates into your production process.
  • Regulatory compliance
    • Depending on the industry, sealants may need to meet specific standards, like FDA food safety, UL fire resistance, ISO certification, or low-VOC environmental regulations. Using a compliant product ensures not only legal adherence but also customer trust and product safety.

What to Consider Next

Sealants do more than just fill gaps. They protect, insulate, and extend the life of products across nearly every industry. With the right formulation, they can take on multiple roles, making your design stronger and more efficient.

Want to learn more about selecting the right sealant for your next project? Let’s talk.

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