Bonding agent is one of the most important auxiliary materials, and it is widely used in packaging operations. Adhesives are sticky substances that connect two separate materials together by virtue of their adhesive properties. There are many types of adhesives.

Introduction
Adhesive is actually a general term for various stress materials that connect or fit the same or different materials. There are mainly three types: liquid, paste and solid.

Classification
There are many types of adhesives, which can usually be classified as follows:

Material source points
①Natural adhesive
It is taken from matter in nature. Including starch, protein, dextrin, animal glue, shellac, leather glue, rosin and other biological adhesives; also including asphalt and other mineral adhesives.
②Synthetic adhesive
Mainly refers to synthetic substances, including inorganic adhesives such as water glass, and organic adhesives such as synthetic resin and synthetic rubber.
Use characteristic points
①Water-soluble adhesive
Adhesives that use water as a solvent mainly include starch, dextrin, polyvinyl alcohol, and carboxymethyl cellulose.
②Hot melt adhesive
It is a solid adhesive for use after the adhesive is melted by heating. General thermoplastic resins can be used, such as polyurethane, polystyrene, polyacrylate, ethylene-vinyl acetate copolymer, etc.
③Solvent-based adhesive
A binder that is insoluble in water but soluble in certain solvents. Such as shellac, butyl rubber, etc.
④Emulsion type adhesive
It is mostly suspended in water, such as vinyl acetate resin, acrylic resin, and chlorinated rubber.
⑤Solvent-free liquid adhesive
It is viscous liquid at room temperature, such as epoxy resin.
Adhesive is the medium between the label material and the bonding substrate, which acts as a link. According to its characteristics, it can be divided into two types: permanent and removable. It has a variety of formulas, suitable for different surface materials and different occasions. Adhesive is the most important component in the technology of self-adhesive materials and the key to label application technology.