What Is a Hot-Melt Adhesive?

A hot-melt adhesive is an adhesive made from thermoplastic, which has to be heated before it can be properly applied to a surface. To dispense the hot-melt adhesive, a special heating gun is used, both to heat the thermoplastic and to dispense it through a nozzle; this comes in both low- and high-temperature varieties. While referred to collectively as glue, there are many different types of hot-melt adhesives on the market, each with special properties. There are many properties associated with these adhesives, such as how long the adhesive will last in the heat gun and how long it takes for a bond to form. All of these things should be known before choosing an adhesive type.

To use hot-melt adhesive, a special type of heat gun is required. This gun has a heating element inside it that converts electricity into heat, so it can melt the adhesive sticks into a usable liquid. These guns come in two main varieties: low- and high-temperature. Low-temperate operates near 250° Fahrenheit (121° Celsius) and is best for cloth substrates; high-temperature operates at 380° F (193° C) and creates a stronger bond. There also are guns that are able to use both temperatures.

While all hot-melt adhesive sticks are commonly referred to as glue sticks, there are many different adhesive types. The most common one for consumers is ethylene-vinyl acetate (EVA), which is low-performance but works fine for many consumers who rarely need glue for heavy-duty projects. Polyolefins are typically low-performance, but they work well with plastics that do not bond well. Polyamides are high-performance and are often used industrially. Each adhesive stick is made with one or two main components and then has additives to increase the adhesive’s efficiency.

There are several special properties attributed to hot-melt adhesive sticks that help consumers and industrial workers know if the adhesive is right for their project. Pot life refers to how stable the adhesive is when melted and whether the glue can char before being dispensed. Melt flow describes how easily the adhesive can flow when molten, with higher levels having weaker bonds. The set time tells users how long it will take the adhesive to set and form a bond.

A special type of hot-melt adhesive stick is known as a pressure-sensitive adhesive. This adhesive at room temperature is solid, like most adhesive sticks. When the operator applies pressure to this stick, usually with his or her fingers, the stick is able to adhere to surfaces. This type of hot-melt adhesive functions on very low-temperature and may char if placed in a heat gun.