Gold in the cold: what’s the best adhesive for cold temperatures?

Adhesives, love them as we do, can be quite sensitive. Barring some exceptions, they tend to cure and perform best at room temperature. Overly hot or cold environments, or ones which involve large fluctuations in temperatures, can cause problems with both curing and post-cure performance. However, with many manufacturers needing adhesive products that do well in the cold, we’ve prepared an article to answer the all-important question: which adhesive is best in cold temperatures?

Cold affects adhesive performance in two key areas: curing, and post-cure. Why is this? Cold makes things contract, stiffen, and become slower, more viscous and therefore more resistant to flow. In terms of curing an adhesive, the molecules needed to induce adhesive cure are slowed down in the cold. This results in a longer curing time for every degree below room temperature you go. Increased adhesive viscosity in the cold also means it takes longer to wet the substrate to be bonded, as well as making adhesives harder to dispense through guns and static nozzles. The general rule of thumb is that for every 8°C (14°F) below room temperature you go (which we generally define as 23°C/73°F), the cure time doubles. Below 10°C (50°F), most adhesives cure poorly, and below 5°C (41°F) almost all hope is lost!

In this article we’ll discuss effective methods for maximising success when using adhesives in the cold, as well as the best Permabond products for curing and performance at low temperatures.

The best adhesive for curing at low temperatures

Let’s start by discussing curing an adhesive at low temperatures. As mentioned earlier, since cold causes adhesive molecules to slow down, curing in the cold takes a lot longer than curing at room temperature. Fear not, however, as there are options available should you need to cure at a lower temperature than this – for example, if you’re bonding something outside in cooler weather.

Permabond ET503 is a fast-curing two-part epoxy adhesive that can be cured at temperatures as low as 5°C (41°F). It bonds to a very wide variety of substrates and has excellent overall environmental durability, offering outstanding strength and toughness. Due to its ability to withstand water, moisture and humidity, it’s ideal for use in outdoor applications. It offers good strength performance in temperatures as low as -40°C (-40°F).

Adhesives that offer continuous cold resistance

Curing an adhesive at room temperature may not be an issue for you, but instead you require an adhesive bond that withstands continuous exposure to low temperatures, and/or can withstand frequent fluctuations in temperature.

Example applications for cold-resistant adhesives:

• Bonding refrigerator and freezer components
• Gas storage vessels (liquefied natural gas, hydrogen, etc)
• Bonding satellite and spacecraft components
• Bonding airplane components
• Cryosurgery and other medical applications
• Oil and gas pipes

There are, of course, many other reasons you may need a cold-resistant adhesive; the examples above are just an overview.

Tips to ensure optimum results when dealing with cold environments

If your project involves an adhesive being exposed to cold temperatures, or fluctuations in temperature, there are several factors that you need to consider before selecting an adhesive to use. These factors include, among others, the following:

• The substrates (materials) you’re looking to bond
• Joint design
• Surface preparation before bonding

Let’s start with substrates, the most important factor. As mentioned earlier, cold causes all materials to contract, and conversely, heat makes them expand. The extent to which materials expand and contract with temperature varies depending on that material’s coefficient of thermal expansion. This matters when dealing with low temperatures as well as large fluctuations in temperature. If one substrate contracts or expands much more with temperature than the one it’s being bonded to, this can eventually lead to adhesive failure as the bond gets stretched out. It is therefore ideal to bond similar substrates when dealing with the cold, with either the same or very similar coefficients of thermal expansion. This page shows the coefficients of many commonly bonded materials.

For the same reason, it’s also ideal to bond your substrates at the temperature in which they’ll be operating. This ensures no subsequent breaking of the bond as the substrates adjust to the cooler environment after bonding. However, as mentioned earlier, if the environment is too cold, curing won’t be possible. What you can consider here, however, is your joint design. It’s best to adopt a joint design that utilises tension or compression forces, and avoids peel or cleavage forces, as these are where adhesives are most vulnerable to failing. Optimum joint design gives cured adhesives the best chance of staying stronger for longer, even when under duress from temperature changes.

Lastly, optimum surface preparation of the substrates before bonding is crucial to ensure good adhesion. Make sure to remove any surface contamination, oxide layers and grease before applying the adhesive. Applying Permabond 2K Primer can help to improve the long-term durability of the bond.

Choosing the right adhesive for your project

You’ve chosen your substrates, optimised your joint design and prepped your surfaces. Now, which adhesive should you choose for the best results? Flexibility is one of the most important features to look for in a cold-resistant adhesive. A product that is too rigid and offers no ‘give’ will be much more likely to weaken or break when faced with cold stress.

Another important feature to look out for is good thermal resistance. Adhesives with this quality tend to not become so viscous in the cold, therefore retaining their ability to flow. Thermal resistance also means an adhesive will more readily withstand thermal cycling and shocks caused by sudden changes in temperature.

The best adhesives for continuous cold exposure and/or temperature fluctuations (post-cure)

We recently launched a new breakthrough UV adhesive, Permabond UV6357. Originally developed for a manufacturer of freezer and fridge components, UV6357 provides excellent adhesion on glass and metals, as well as on rigid thermoplastics such as ABS, PVC and Nylon. Its outstanding thermal resistance means it withstands thermal cycling and shock, making sure that bonded joints remain flexible when subjected to temperature changes. It has high reactivity and will cure even when the UV light is filtered by the substrate, such as when bonding fritted glass.

Permabond ET5428 is a thixotropic two-part epoxy that provides outstanding performance at both elevated, and very low temperatures. On a recent overlap shear test conducted on CFRP at -40°C (-40°F), ET5428 retained 13MPa (1885 psi) of tensile strength. The adhesive also offers excellent resistance to impact and vibration, bonds a very wide variety of substrates and is a fantastic all-rounder. It’s particularly beneficial in bonding composite materials and is one of our most popular products.

Other products you might want to consider are Permabond MT- modified epoxies and MS polymers. These products offer more flexibility than other adhesive chemistries. For a faster cure, consider using an MMA (methylmethacrylate adhesive). In addition to curing quickly, these adhesives are toughened with rubber, meaning they offer really high bond strength as well as great thermal resistance.

Another thing to remember is that we can custom make a product to suit your exact project needs. If this is something you’d be interested in, please get in touch with us.

Final Thoughts

Bonding both in the cold and for the cold can be a challenging, complex task. It can be made less so by thorough consideration of substrates, joint design and of course, adhesive choice. Permabond is able to provide a solution in the vast majority of low-temperature applications – if you’d like to discuss your project with us, please don’t hesitate to contact us.