What is hotmelt adhesive?

Hot melt adhesive has the main component of thermoplastics. In ambient conditions, adhesive exists in a solid state, using hot melt adhesive requires specialized heating equipment to transfer the adhesive from a solid to a liquid state. After applying the adhesive to the surface of the material, the adhesive wets the surface of the material (wetting) then the adhesive will dry (solidification) and return to its original state and create a cohesion between the material surfaces. Depending on the different types of material surfaces, we can choose a suitable hot-melt adhesive.

Image 1: Types of hot melt adhesive

Advantage of hot melt adhesive

Hot melt adhesives create quickly bonding surface materials together (hot tack) and can be used in automatic, semi-automatic machines as well as a variety of methods of applying adhesive such as nozzle, spray, roller, wheel.

Image 2: Glue machine system

Physical parameters

The physical parameters that are particularly important in the production and use of hot melt adhesives such as viscosity, softening point, open time, set time.

The viscosity of hot melt adhesives ranges from a few hundred Centipoises (mPa.s) to million of Centipoises The low viscosity is suitable for kinds of applying methods such as spraying, roller, wheel methods. The higher the viscosity, the harder production so that the method of applying the adhesive is mainly using rollers or wheels. The higher the temperature the lower the viscosity of adhesive, which greatly affects to use of the adhesive with the proper temperature for the particular application and manufacturer's recommendations.

The softening point: is the temperature of the adhesive in which the hot melt adhesive begins to change its physical state from the elastic region to the molten zone. This is an important factor in the selection of adhesive suitable for heat resistance applications.

Open time: is defined as the time period from when the adhesive is applied to the surface of the material until the adhesive still creates an adhesion with the other surface.

Set time: is defined as the time it takes for two surfaces to form to adhere together and to create a satisfactory adhesion.

Open time and setting time to depend on four main factors:

  • Substrate
  • Adhesive
  • Amount of adhesive
  • Temperature

Using hotmelt adhesive

Hotmelt adhesive is widely used in production and life from silicone adhesive using conventional glue guns to make handmade items to automatic systems using granule hot melt adhesive, PSA, and semi-PSA adhesive for carton packaging, confectionery boxes, soft packaging, labeling, bookbinding, MDF, HDF laminating.

The hot melt adhesive has gradually replaced the methods of using traditional tapes because of increasing productivity and increasing the aesthetics of the packaging. In addition, hotmelt adhesive is also widely used in the production of diapers, tampons, tissue boxes, mattresses ...

To know more about the specific application of each type of hotmelt adhesives, you can refer here