Adhesives and sealants are found everywhere, with various strengths according to their applications. Adhesives in the aerospace industry are typically more volatile than normal products. This makes it imperative to understand the proper methods for storing and transporting adhesives and sealants used for aerospace applications.
What Are Adhesives and Sealants?
Adhesives and sealants are tacky substances that chemically bond and seal materials together. Adhesive types are categorized by whether or not they are reactive.
Reactive adhesives rely on chemical interactions to bond materials to one another:
- Natural adhesives: These are made of animal gelatin or material derived from vegetables. They are classified as basic glues.
- One-part and multi-part adhesives: This category of adhesive creates bonds through chemical reactions that can occur within a single adhesive or when two or more adhesives are mixed together.
- Synthetic adhesives: These adhesives are made of a variety of materials and are usually very reactive. Some common synthetic adhesives include polyurethane, epoxies and acrylic polymers.
Non-reactive adhesives use elements like heat or pressure to harden into a bond, rather than a chemical reaction. Non-reactive adhesives include the following:
- Contact adhesives: These adhesives are made of rubber or its variants. They are attached to each surface and pressed together for a rapid bonding.
- Drying adhesives: These need air to become solid as the solvent in the adhesive undergoes evaporation.
- Hot-melt adhesives: With these adhesives, a bond is formed after applying the adhesive in molten form and waiting for it to cool.
- Pressure-sensitive adhesives: For these adhesives to create a molecular bond, pressure must be applied to the materials being adhered. Pressure-sensitive adhesive is typically used where a permanent bond is not desired.
Sealants form a mechanical seal to stop fluids from entering through surfaces, joints or other openings in a material. While sealants are not adhesives, many have adhesive properties and are referred to as “structural sealants” or “adhesive sealants.”
In some cases, adhesive can be a substitute for sealant when it keeps out water and air. An adhesive’s ability to act as a sealant relies on the materials to be bonded and the sizes of the surfaces.
Are Adhesives and Sealants Considered Hazardous Materials?
Adhesives and sealants can be flammable and pose health hazards to humans in storage and transport. Solvent-based and chemically reactive adhesives require particular attention to safety measures due to their hazardous nature.
Adhesive and sealant manufacturers must indicate the possible hazards of a product in its safety data sheet (SDS). They must also list the product’s storage conditions and shelf life in the technical data sheet. Because there are so many adhesion systems on the market, there is no way to create universal guidelines for storing adhesives. Distributors must check the details of each product and take appropriate precautions based on the hazards indicated in product sheets.
How Are Adhesives and Sealants Used in the Aerospace Industry?
Adhesives have a wide variety of uses in the manufacturing of air and spacecraft. One use for adhesives in aerospace industry applications is the creation of conductive circuits. Such adhesives produce electrical or thermal conduction by incorporating metal flakes, like silver.
Additional applications for aerospace adhesives include the production of:
- Electronics assemblies
- Fuel assemblies
- Fiber and metal composites
- Optical fibers
- Transducer seals
Aerospace sealants are used in applications including:
- Fuel tank sealing
- Cabin pressurization
- Electrical encapsulation
- Window and access door sealing
- Form-in-place gasketing
Hazardous Material Classifications for Adhesives and Sealants
Adhesives and sealants may have toxic or flammable properties, so any business that stores or transports them needs to take appropriate precautions for both legal and safety reasons. Please note that the below text is meant only as reference material – consult your freight team/forwarding partner for all requirements.
The Department of Transportation (DOT) uses the United Nations model for hazardous material classification. There are nine classes of material that require specific labeling during shipping:
- Class 1 Explosives: This class requires a yellow-orange diamond label that classifies the divisions of explosives being carried.
- Class 2 Gases: This class has a yellow label for oxygen, a red label for flammable gas, a green label for non-flammable gas and a black and white label for inhalation hazards.
- Class 3 Flammable Liquids: This class has four red diamond labels with fire symbols and the terms gasoline, flammable, combustible and fuel oil.
- Class 4 Flammable Solids: Depending on the division, this class has a red and white striped flammable label, a light blue dangerous label and a half white and half red spontaneously combustible label.
- Class 5 Oxidizing Agents and Organic Peroxides: This class has three divisions with a yellow oxidizer label, a yellow organic peroxide label and a half red and half yellow organic peroxide label.
- Class 6 Toxic and Infectious Substances: This class has white and black symbols with a skull and crossbones to indicate poison and inhalation hazards.
- Class 7 Radioactive Substances: This class has a single diamond label with the radioactive symbol over a yellow background and the word radioactive over a white background.
- Class 8 Corrosive Substances: This class has a symbol of a test tube of dangerous substances with the term corrosive displayed prominently.
- Class 9 Miscellaneous: This class label shows black and white vertical stripes in the top half and white space in the bottom half.
Adhesives fit in Classes 3, 4, and 6, depending on their composition. Check the label of the adhesive or sealant to determine if it needs specific treatment. When shipping sealants or adhesives that are flammable or toxic, you must obtain placards that indicate the material is Class 3 or 4 Flammable or Class 6 Poisonous. Speak to someone at your post office or shipping company to find out how to get authorized for the placards and obtain them.
Safely Storing and Transporting Adhesives and Sealants
When transporting or shipping sealants and adhesives, keep the following reference guidelines in mind, but always confirm requirements with your freight team/freight forwarding partner:
- Never ship sealants or adhesives with other materials that could create a reaction leading to explosion or ignition.
- Research guidelines about transporting multiple hazardous chemicals in the same vehicle or ship, and take care to follow them.
- Secure all sealants and adhesives inside the transport vehicle to ensure they do not fall out or shift unnecessarily during transport. Some formulations are volatile and could cause an explosion or create ruptures and leaks within the container if not secured.
- Ensure all transport vehicles moving sealants and adhesives have signage alerting material handlers, passengers, drivers and others to the potential dangers of the material carried.
- Ensure drivers transporting adhesives and sealants have appropriate, up-to-date licensing and have passed a thorough training course on handling hazardous materials and the potential emergencies related to them.
- Ensure drivers keep logs of the types and amounts of chemicals to be transported, and that they consistently complete the necessary paperwork at the point of delivery.
One more critical consideration for storing and transporting adhesives or sealants is temperature. Conditions in cargo ships and even smaller delivery vehicles can easily become hot enough to cause dangerous reactions or degrade the product’s adhesive or sealing qualities. For optimal safety, it’s important to choose refrigerated container units that ensure temperature stability.
Talk to a Specialist at Klinge Corporation
If you store or transport aerospace adhesives and sealants, safety should be your first priority. Klinge Corporation’s line of specialized refrigerated transport containers includes units that are dependable for any industry. Our management system is ISO 9001:2015 certified, as is our quality assurance program. To find out which transport container products are right for your aerospace adhesive and sealant transport needs, contact Klinge Corporation and request a quote today. We are proud to provide world-class service to match the quality of our products.