【 Hot Melt Adhesive Formula 】 How is hot melt adhesive prepared?

Based on thermoplastic polymers, the properties of hot melt adhesives allow them to melt at high temperatures and then return to a solid state when the ambient temperature is reached. Hot melt adhesive has a wide range of applications, and its formula has obvious advantages over traditional adhesives. They can be combined with almost anything, making them a common choice for various industrial and commercial applications.

In most cases, you will see hot melt adhesive sold as small round hot melt adhesive particles of different lengths. Applications are usually accomplished using hot-melt equipment, but in appropriate cases, spraying or impregnation are other methods.

Professional industrial hot melt adhesives hold solid hot melt adhesives and melt them with internal heating elements. The operation of the equipment is very simple – pressing the mechanical trigger mechanism will force the molten glue to be squeezed out of the heated nozzle.

When it is first sprayed out, the temperature of the glue is high enough to burn the skin upon contact. For non-customized hot melt adhesives, complete curing takes several seconds to several minutes.

Customized hot melt adhesive applications Hot melt adhesives are widely used in daily industries. You may not be aware of this, but any assembled product you encounter is very likely to be at least partially bonded with hot melt adhesive. Here are some recognizable examples:

Electronic Products: Wire bonding and Packaging

Automobile: Seat Assembly and Interior

Packaging: Pallet stabilization, packaging, sealing and sealing of boxes and cartons

Electrical Appliances: Gasket Installation and decoration

Furniture: Panel and Cabinet Assembly

Why are hot melt adhesives better? Solvent-based adhesives lag far behind the advantages of hot melt adhesives. Without curing, VOCs are eliminated or reduced. Usually, there are no specific disposal regulations, and their shelf life is much longer. Furthermore, during the brief solidification period, the layer thickness was not lost. However, hot melt adhesive is not without its drawbacks. Without changing the formula, some hot melt adhesives are very sensitive to temperature, environmental changes and chemicals. In some cases, this may lead to a complete loss of adhesive force.

Depending on the application of the adhesive, different strengths, curing times, open times and viscosities may be required. The greatest advantage of using hot melt adhesive might be the ability to create custom formulas that are perfectly tailored to the task at hand.

Modifying the base polymer and additives is the first step in creating a new custom hot melt adhesive formula. Different polymers perform better than others on specific materials and resins. Not only can the structure of the adhesive be changed, but also properties such as low odor emission, color, odor, enhanced flexibility and higher transparency can be increased by adding special tackifying resins. The basic process of configuring a hot melt adhesive formula is as follows:

Polymers are typically selected from n-butyl ethylene-acrylate, styrene block copolymers, ethylene-vinyl acetate, polyethylene, polypropylene, polyester, and polyamide or polyolefin. The higher the percentage of polymer content, the higher the viscosity. A higher viscosity provides excellent toughness and flexibility.

The viscosity of a viscosity-increasing resin adhesive is called “viscosity”. The resin added to the polymer will determine how strong your viscosity is. If you prefer to reduce viscosity, you can add more resin to the mixture.

The choice of resin depends on its compatibility with the polymer you select. Commonly used resins include C9, C5, pure aromatic monomers, rosin, hydrogenated rosin, rosin esters, terpene phenolic resins and hydrogenated hydrocarbons.

The next step in this process is to add wax. The main purpose of using wax as an additive is to control the open time and set the speed. The solidification speed is defined as the length of time required before reaching the appropriate bonding strength. Open time refers to the length of time required to establish a key, which can range from a few seconds to an infinite length.

Wax is also responsible for influencing adhesion and heat resistance at temperatures lower than the ambient temperature. The more wax is added to the mixture, the stronger the bonding force, the higher the viscosity and the slower the solidification time. Waxes can be synthetic, natural or microcrystalline.

The next two main components are antioxidants and plasticizers. Plasticizers ensure that the formula has significant strength and flexibility. They are usually hydrocarbon oils with chemical properties similar to paraffin.

Antioxidants protect the glue by preventing degradation, just as they protect the human body. BHT, phosphate, phenol, phosphite; Aromatic amines are common antioxidants.

Other properties can be achieved by choosing to add components such as flame retardants, fillers and biocides.