The best high heat adhesive options for industrial use

Adhesives are chemical substances made up of polymers - effectively, large molecules made out of much smaller molecules called monomers. As with most materials, being subjected to heat causes these molecules to gain energy and start to move more freely. For adhesives, this increased molecular activity leads to softening (and eventually melting in thermoplastic adhesives) and reduced bond strength.

The temperature at which an adhesive transitions from a hard, glassy state into a softer, more rubbery one is known as its glass transition temperature, or Tg for short. Generally speaking, the higher an adhesive's Tg, the better its heat resistance.

Another key problem to consider is differential thermal expansion and contraction. Some materials expand and contract more with temperature changes than others do - this is known as a material's coefficient of thermal expansion, or CTE. Metals such as stainless steel, for example, have a much lower CTE than nylon, meaning that steel will expand and contract far less than nylon when heated and cooled.

When bonding substrates with differential CTEs like these together, this can create stress and breakages at the bond joint as one substrate effectively stretches the bond out. Thermal cycling, a process where a product is subjected to hot and cold cycles, causes particular issues when bonding unalike materials.

Therefore, a heat-resistant adhesive ideally needs to be able to withstand the process of heating, all the while continuing to offer strong bond strength. Permabond offers adhesives across a range of chemistries that offer good heat resistance.

High heat adhesive chemistries

Permabond only makes adhesives using organic chemistry (such as epoxies and acrylics). Most modern, high-performance adhesives fall into this category. However, organic adhesives are by their nature limited in terms of how much heat they can withstand - anything above 300degC, and they will fully degrade. Nevertheless, there are many industries and applications that don't require temperatures as high as this, and Permabond has an assortment of products that can help in these cases.

Before choosing an adhesive, it's important to evaluate your substrates. Are they delicate, likely to be damaged or changed by heating? Or are the substrates you're looking to bond vastly different, with different rates of thermal expansion and contraction? These things will play a vital role in the success of your bond, not just the adhesive you choose.

Single-part epoxies

1-part epoxies are a good candidate for an application requiring high heat resistance. They provide strong bonds on a variety of substrates including metals, composites and some plastics. They require heat to cure anyway, which is normally done at temperatures between 80 and 150degC. Because of this, all 1-part epoxies offer a good level of heat resistance as standard.

Permabond ES5516 is a one-part epoxy launched at the beginning of 2025. Developed with the ever-growing EV market in mind, ES5516 excels at bonding electric motor magnets (such as class H magnets designed to withstand up to 180degC) as well as in other high-heat applications like boilers and sensors.

Two-part epoxies

Often used in the automotive and aerospace industries, among others, 2-part epoxies cure fully at room temperature. Offering similar benefits to 1-part epoxies in terms of strength, durability and versatility, these need to be mixed before bonding and can be heated to accelerate curing times. In fact, it's often recommended that 2-part epoxies are heated in an oven post-cure before subjecting them to heavy loads at high temperatures - this enables the development of a stronger polymer matrix in the cured adhesive through additional crosslinking.

An exception to this rule is Permabond ET5424 - another new adhesive launched earlier this year! Permabond ET5424 cures fully at room temperature, with high performance at temperatures as high as 230degC and as low as -40degC. As the cured adhesive is heated up, it increases in strength as other two-part epoxies do - however, it doesn't need to be oven cured beforehand to ensure a strong bond at high heat.

Designed primarily for automotive and aerospace applications, ET5424 is a high heat adhesive with low outgassing and highly suited for paint baking/powder coating applications.

Structural acrylic adhesives

Products such as Permabond TA437 offer very high strength on motor magnets, as well as on most metals, ferrites and ceramics. It has excellent heat resistance, retaining very high strength even at 200degC. TA437 will also cure anaerobically when bonding metal to metal in a tight-fitting gap.

Cyanoacrylates

Cyanoacrylates, also known as superglue, cure rapidly at room temperature via interaction with moisture. They're very easy to dispense and apply and set in seconds, providing a strong bond on many materials. However, most cyanoacrylates are not heat-resistant adhesives. For those that are, the majority require a post-cure, where after initial curing, the bonded parts are subjected to a high temperature for a time in order to 'sensitise' them to high heat. This is often effective, but can be time-consuming and more expensive; a drawback in high speed production lines.

An exception to the post-curing rule is Permabond 825, a high heat-resistant cyanoacrylate adhesive. This low-viscosity product offers high strength at up to 200degC and bonds well to plastics and metals. It also has excellent strength retention during thermal aging. Due to its very quick cure, 825 is very well suited to high speed production lines.

Other adhesive chemistries can be used in some cases, but the above four are the ones Permabond most frequently recommends.