Why Does Superglue Get Hot When Drying?

When you apply superglue to a surface and it dries or hardens, you may notice that it gets hot. This heat is a fascinating by-product of the chemical process that takes place, known as curing. In this article, we will explore the science behind this phenomenon and explain why superglue gets so hot as it dries.

The Science Behind the Heat

Superglue, a type of adhesive known scientifically as cyanoacrylate, undergoes a chemical reaction to form a hard polymer when it dries. This process, known as curing, is an exothermic reaction, meaning it releases heat as it progresses. The main component of superglue is ethyl 2-cyanoacrylate, which, when combined with moisture (such as water vapor in the air or trace water present in the adhesive itself), undergoes a polymerization reaction to form a hard, sticky polymer.

Role of Water

Water plays a critical role in the curing process of superglue. It acts as a catalyst, allowing the monomers (the single-unit building blocks of polymers) to combine and form the polymer. Without water, the monomers would not bond, and no adhesive effect would occur. The water in the environment or the superglue itself is crucial for starting the chain reaction that leads to polymerization.

Chain Reaction and Bonding

Most superglues are based on ethyl 2-cyanoacrylate paired with an acidic inhibitor. This inhibitor is typically added to prevent premature curing or self-adhesion before the glue is applied. When water comes into contact with the superglue, it dissolves the inhibitor, allowing the monomers to start bonding and form the polymer. This chain reaction leads to the formation of a strong bond with the surface to which the glue is applied.

Heat Release during the Reaction

The exothermic nature of the polymerization reaction means that heat is released as the monomers combine to form the polymer. This heat is a by-product of the chemical reaction and is what causes the superglue to feel warm to the touch as it cures. The amount of heat released can vary depending on the specific formulation of the superglue and the presence of moisture.

Examples of Exothermic Reactions in Everyday Life

The process of superglue getting hot when it dries is not unique. Other materials, such as concrete and fiberglass, also undergo similar exothermic reactions during curing. In concrete, the hydration of cement is an exothermic process that releases heat. Similarly, fiberglass epoxy cures through a polymerization reaction that also generates heat.

Conclusion

In summary, the temperature rise in superglue when it dries is due to an exothermic chemical reaction called curing. Water acts as a catalyst, dissolving the inhibitor and allowing the monomers to bond, forming a polymer. This process releases heat as a by-product, making the superglue feel warm to the touch. Understanding the science behind this phenomenon can help in the proper application and curing of superglue and similar materials.