A Deep Dive into Aerospace Adhesives: Comparing Epoxy, Cyanoacrylate, Polyurethane and Silicone

Comparing Aerospace Adhesives: The SkyGeek Guide

Adhesives play a critical role in the aerospace industry. They're responsible for bonding various components of aircraft, spacecraft and satellites together, ensuring these high-performance machines can withstand the extreme conditions they're exposed to during the flight. This SkyGeek guide (with FAQ) to common aviation industry adhesives is based on our long experience serving the needs of individuals, aerospace companies, commercial airlines, military installations, government customers and fixed-base operations.

Aerospace adhesives must provide strong bonds, resist extreme temperatures and be lightweight to minimize the impact on overall performance. Additionally, they must adhere to strict industry standards for safety and reliability. That means adhesives in aerospace aren't just glue - they're critical components of engineering precision and safety. Whether you're assembling fuselage components or just patching a panel, your adhesive choice matters.

Over our 40-plus years of operations, we have developed expertise in the advantages and disadvantages of commonly used aerospace adhesives. Use this guide to learn about four common types of aerospace adhesives: epoxy, cyanoacrylate, polyurethane and silicone. We'll also help you navigate which adhesive is best suited for your project, whether you're bonding composite wing panels or mounting an interior panel.

About Epoxy Adhesive

Epoxy adhesives are one of the more popular choices for aerospace applications due to their exceptional mechanical strength and resistance to harsh environmental conditions. Find more than 200 kinds of epoxy adhesives at SkyGeek, ranging from 50-gram E-Z packs of Henkel Hysol red epoxy adhesive to gallon kits of epoxy paste adhesive by Solvay. These adhesives are often used in primary and secondary structural bonding, offering performance that meets rigorous aerospace requirements for safety in the skies.

Advantages of Epoxy Adhesives

• High bond strength, making them ideal for structural bonding applications.
• Excellent resistance to chemicals, heat and moisture.
• Wide range of formulations, allowing for customization to suit specific application requirements.
• Generally low shrinkage during curing, resulting in minimal stress on bonded components.
• Outstanding durability over time, even under load-bearing conditions.

Disadvantages of Epoxy Adhesives

• Longer curing times compared to other adhesive types
• It might require heat or pressure to cure effectively
• Can become brittle at very low temperatures
• Some types may require careful surface preparation for optimal adhesion

About Cyanoacrylate Adhesives

Cyanoacrylate adhesives, often referred to as "super glues," provide quick bonding times and strong adhesion for a variety of materials. Cyanoacrylate adhesives from SkyGeek include inexpensive 1-oz. bottles by Permabond and cyanoacrylate gel adhesives in 7-oz. tubes by Henkel's Loctite® brand. They're perfect for small-scale applications and quick fixes where speed is more important than long-term load-bearing performance.

Advantages of Cyanoacrylate Adhesives

• Rapid curing, usually in seconds to minutes.
• Excellent bond strength for small, non-structural components.
• Can bond a wide variety of materials, including plastics, metals and composites.
• Easy to apply, often without the need for complicated equipment.
• Ideal for minor repairs, field fixes, or temporary solutions during maintenance.

Disadvantages of Cyanoacrylate Adhesives

• Limited thermal and chemical resistance compared to other aerospace adhesives.
• Can become brittle over time, reducing long-term bond strength.
• Not suitable for large, structural bonding applications.
• May produce fumes, so must be used with proper ventilation.

Polyurethane Adhesives

Polyurethane gets its name from its definition: a class of organic chemical polymers joined by urethane links. Polyurethane adhesives offer a combination of flexibility and strength, making them suitable for a range of aerospace applications. They're often used where vibration, movement or thermal expansion is expected.

Advantages of Polyurethane Adhesives

• Excellent flexibility, allowing for the absorption of stress and vibrations.
• Good adhesion to a variety of materials, including plastics, metals and composites.
• Can be formulated to meet specific application requirements.
• Generally resistant to moisture, chemicals and abrasion.
• Ideal for interior panel bonding and non-structural applications.

Disadvantages of Polyurethane Adhesives

• Can require a primer for optimal adhesion on certain surfaces.
• Can be sensitive to UV light, which may cause degradation over time.
• Lower temperature resistance compared to epoxy adhesives.
• Not always suitable for exterior or high-heat applications.

About Silicone Adhesives

Rubber-like silicone is a polymer made of siloxane. Although it acts like rubber, it's considered a chemical middle ground between rubber and plastic. It's also chemically stable, so silicone implants are popular plastic surgery choices.

Silicone adhesives are known for their excellent temperature resistance and flexibility, making them ideal for applications where thermal expansion and contraction are concerns. Silicone adhesives shine in sealing applications, gasketing, and anywhere temperature extremes are the norm.

Advantages of Silicone Adhesives

• Strong temperature resistance, capable of withstanding extreme fluctuations.
• Excellent flexibility, allowing for movement between bonded components.
• Good resistance to moisture, chemicals and UV light.
• Can be formulated as one-part or two-part systems, providing options for curing times and application methods.
• Non-corrosive formulas available for electronics or sensitive surfaces.

Disadvantages of Silicone Adhesives

• Generally lower bond strength compared to epoxy, cyanoacrylate and polyurethane adhesives.
• Longer cure times, particularly for one-part systems.
• Might require a primer or surface treatment for optimal adhesion on certain materials.

Aerospace adhesives play a vital role in modern aircraft, spacecraft and satellite manufacturing and maintenance. Understanding the characteristics, advantages and disadvantages of these adhesives can help engineers choose the right adhesive for the job. When in doubt, consult SkyGeek - because sticking things together is kind of our thing.

Aerospace Adhesives FAQ

What factors should be considered when selecting an aerospace adhesive?

Key factors to consider include bond strength, temperature resistance, chemical resistance, cure time and the materials being bonded. Other considerations may include flexibility, durability under stress and compatibility with surrounding components or surface finishes. Application method and required certifications can also influence adhesive selection.

Are there any industry standards for aerospace adhesives?

Yes. Aerospace adhesives must meet specific industry standards, such as those outlined by the Federal Aviation Administration (FAA) and other international regulatory bodies. These standards ensure performance, reliability and safety in extreme operating environments. Common certifications may include MIL-SPEC, AMS and ASTM compliance.

Can aerospace adhesives be used for other industries?

While aerospace adhesives are specifically formulated for aerospace applications, some can be used in the automotive, marine and electronics industries. Their high performance makes them ideal for situations requiring strong bonds and resistance to environmental stressors, even outside the aerospace sector.

How do I determine the appropriate cure time for an aerospace adhesive?

Cure times vary depending on the adhesive type, formulation and application requirements. Consult the manufacturer's technical data sheet for specific information about cure times.

Do aerospace adhesives require special equipment for application?

Some aerospace adhesives may require specialized equipment for application. That equipment can range from dispensing systems to ovens to presses. Others can be applied using manual application equipment or standard automated dispensing systems.