Table of Contents
- The Importance of Proper Storage
- General Rules for Storing Structural Adhesives
- Epoxy Adhesive Storage Guidelines
- Methyl Methacrylate Adhesive Storage Guidelines
- Acrylic Adhesive Storage Guidelines
- Cyanoacrylate Adhesive Storage Guidelines
- Signs Structural Adhesives Have Gone Bad
- FAQs
Structural adhesives are designed for high-strength bonding applications, and if the bond fails, it could lead to serious consequences. While many businesses focus on proper application of their adhesives, some forget that proper storage of structural adhesives can be just as important. Even the best or strongest structural adhesive can fail if it is stored incorrectly.
Fortunately, storage errors with structural adhesives can typically be avoided. Our team walks through how to store epoxies, methyl methacrylates, cyanoacrylates, and acrylic adhesives for optimal performance.
The Importance of Proper Storage for Structural Adhesives
Proper storage can have a direct impact on the performance of structural adhesives, but many businesses underestimate just how much of a role storage can play. From our experience, bond failures are often blamed on surface preparation or adhesive application, but they are often rooted in storage issues. Especially because many structural adhesives come in two parts that rely on a chemical reaction between the two components, proper storage is critical to their success.
When storage guidelines are ignored, even unopened adhesives can start to degrade. Improper storage can impact the adhesive’s cure speed, viscosity, consistency, and strength. These effects can lead to premature curing, poor performance, a shortened shelf life, or ultimately bond failure. In some cases, improper storage of reactive structural adhesives can also be a safety hazard.
For businesses, all of these effects can be extremely detrimental. Wasted materials, faulty final products, and safety incidents can lead to significant financial costs and operational problems. Instead of neglecting storage, businesses should treat it as part of the bonding process for best results.
General Rules for Storing Structural Adhesives
While different adhesive chemistries and products have different storage recommendations, there are some general rules of thumb for storing structural adhesives.
If you want to optimize their performance, some general tips on how to store structural adhesives include:
- Keep adhesives in their original, unopened containers until ready to use
- Avoid extreme temperatures (manufacturers usually provide a recommended temperature range)
- Refrigerate the adhesive if recommended and allow time to return to room temperature before use
- Limit exposure to moisture, humidity, and direct sunlight
- Keep separate adhesive component containers together to avoid confusion
- Follow a first-in, first-out inventory management system
- Clearly label containers with receipt and expiration dates
- Review the technical and safety datasheets for every adhesive you stock
- Assign dedicated storage areas for flammable or reactive products
- Test the adhesive before application, especially if nearing the expiration date
With these storage protocols in place, you have a baseline for safe and proper storage of structural adhesives. You can then fine-tune your storage based on the adhesive chemistry or specific adhesive product.
Epoxy Adhesive Storage Guidelines
Epoxy adhesives can be one-part or two-part adhesives that include a resin and a hardener. They are known for their great strength, but improper storage of epoxy adhesives can decrease their effectiveness and lead to costly performance issues.
While epoxies are relatively stable compared to other adhesive chemistries, they are still sensitive to temperature extremes and moisture. Epoxy adhesives should be stored at room temperatures up to about 75°F unless the manufacturer specifies otherwise. Prolonged exposure to colder temperatures may lead to crystallization, and heat can cause degradation of the epoxy.
For best results, some tips on how to store epoxy adhesives so they last longer include:
- Keeping the containers tightly sealed when not in use
- Storing the adhesives at the recommended temperature, depending on the adhesive
- Keeping the adhesives in a well-ventilated area away from excessive moisture
- Storing both components next to one another to prevent mix-ups of two-component epoxies with separate packaging
- Inspecting the components for crystallization before use
If you follow these storage tips for epoxy adhesives, the shelf life is anywhere from 6 to 24 months unopened. Of course, the shelf life of an epoxy adhesive will depend on the type of epoxy and the specific product.
Methyl Methacrylate Adhesive Storage Guidelines
Methyl methacrylate adhesives, or just MMAs, are a diverse collection of adhesives known for their fast-curing capabilities. They are made up of MMA monomers and activators. While they require minimal surface preparation, they can be more chemically reactive than some other structural adhesives, which is important to keep in mind when you store MMA adhesives.
In general, considerations for storing MMA adhesive glues include:
- Keeping the adhesives in a cool and well-ventilated area below 75°F (cold storage may be recommended)
- Checking safety datasheets for flammability issues and storage recommendations
- Storing both components next to one another to prevent mix-ups of two-component adhesives with separate packaging
- Avoiding direct sunlight exposure
In general, the shelf life of MMA adhesives is around 6 to 12 months at room temperature but MMA adhesives may last longer if stored in refrigerated compartments. If you store methyl methacrylate adhesives in colder temperatures, move them to room temperature to warm before using, usually 24 hours before application.
Acrylic Adhesive Storage Guidelines
Structural acrylic adhesives are the broader category of adhesives composed of acrylic polymers. They usually come in two-part systems with a base and a reactor and include MMAs. Structural acrylic adhesives can have diverse properties based on the specific adhesive, so specific storage requirements can vary.
In general, structural acrylic adhesives storage considerations include:
- Keeping the adhesives in a cool and well-ventilated area below 75°F (cold storage may be recommended)
- Checking safety datasheets for flammability issues and storage recommendations
- Storing bulk acrylic adhesive components next to one another to prevent mix-ups
- Avoiding direct sunlight exposure
When stored properly, the shelf life of acrylic adhesives can be anywhere from 6 to 18 months depending on the brand and product. Prolonged exposure to higher temperatures can decrease shelf life, whereas cold storage may increase shelf life. If storing acrylic adhesives in refrigerated compartments, the adhesive should be moved to room temperature before using to have time to warm up. Often 24 hours is recommended.
Cyanoacrylate Adhesive Storage Guidelines
Cyanoacrylate adhesives, often called instant adhesives, are known for their fast bonding. They cure in the presence of moisture, so they can be especially sensitive to moisture and humidity.
Best practices for storing cyanoacrylate adhesives typically include:
- Keeping containers tightly sealed when not in use
- Storing in dry environments with controlled humidity
- Storing at room temperature or refrigerating if recommended
- Keeping away from direct sunlight
The shelf life of cyanoacrylate adhesives that are unopened is usually between 8 and 12 months as moisture will eventually seep into the container. Opened containers of cyanoacrylate adhesives could have a shelf life as short as 6 weeks. Refrigeration may increase shelf life, but the adhesive should not be frozen. Refrigerated cyanoacrylate adhesives should be left at room temperature before being used to allow time to acclimate.
Remember, these storage guidelines are just general recommendations. Every adhesive is different, so it is important to follow the recommendations as outlined by the adhesive manufacturer for the best results.
Signs Structural Adhesives Have Gone Bad
Even when stored carefully, structural adhesives can start to degrade over time. Especially as you near the expiration date, it is important to recognize when a structural adhesive will no longer be effective for your application. Some issues are subtle, while others are clear indicators that the adhesive should no longer be used. Using a bad adhesive can lead to wasted materials, rework, and bond failure that can cost your business time and money.
Some common warning signs that a structural adhesive may have gone bad include:
- Noticeable changes in viscosity, such as thickening, separation, or graininess
- Crystallization or cloudiness in normally clear products
- Unusual odor or color changes compared to a new container
- Excessive bubbles after mixing
- Longer cure times or failure to cure at all
- Difficulty dispensing or uneven mixing from cartridges
When in doubt, test the adhesive on a non-critical sample before use. If issues arise, replacing the expired or questionable adhesive is far less costly than risking bond failure.
Have Questions?
Proper storage of structural adhesive glues is a simple way to help ensure optimum performance, and we encourage you to treat structural adhesive storage as just another part of the bonding process, instead of an afterthought. Every adhesive chemistry is unique, so it is important to understand the differences to prevent problems.
If you are experiencing issues or have more questions about your adhesive’s performance, feel free to contact us. Our adhesive experts have worked with a wide range of structural adhesives with different needs and requirements.
