As occurs in paints and coatings, adhesives consist of various chemical components where each of these compounds has a specific function. In addition to the main polymer that provides the main properties of an adhesive, there are other compounds such as additives and fillers that add specific properties to the adhesive.
The adhesives are polymers that can be classified into two major groups according to the manner in which cross linking or curing reached: chemical curing adhesives and physical curing adhesives.
Chemical curing adhesives reach their cured or crosslink by a series of chemical reactions (polyaddition, polycondensation or polymerization) that occur internally between the monomers, such adhesives are composed by the following compounds:
Monomers: These are the basic units that form the polymers. Once the monomers bond with others monomers to produce polymers, polymers can adopt the structures and properties of thermoplastics, elastomers and thermosets materials. The resin, catalyst and reactive diluents are also considered as monomers.
Prepolymers: Prepolymers are polymer chains with small length and weight, primarily used for adhesives such as polyurethane and unsaturated polyester adhesives.
Fillers: Fillers are chemicals compounds which vary primarily the mechanical properties of adhesives. The fillers most used in the adhesives include silica, clay, aluminum powder, etc. The correct selection of fillers will directly affect the physical, chemical and mechanical properties of adhesives, glues or sealants.
Pigments: These are the chemical compounds that give the color to the adhesive. Due to the pigments, we can use the same adhesive with the same properties but the different colors.
Additives: Additives are chemical compounds that vary the chemical properties of the adhesives. Accelerators, corrosion inhibitors, adhesion promoters, fire retardants and fungicides are considered as additives in adhesives.
Physical curing adhesives are the adhesives that contain the polymers already formed, but need an energy (heat, pressure, etc.) to produce the adhesion and curing process. This kind of adhesives are composed by the following compounds:
Polymer: This is the main polymer that form and produce the adhesive. Once it crosslinks, the polymer can adopt structures and properties of thermoplastics and elastomer materials. These adhesives don’t contain polymers with thermosets material structures.
Fillers: Fillers are chemicals compounds which vary primarily the mechanical properties of adhesives. The fillers most used in the adhesives include silica, clay, aluminum powder, etc. The correct selection of fillers will directly affect the physical, chemical and mechanical properties of adhesives, glues or sealants.
Pigments: These are the chemical compounds that give the color to the adhesive. Owing to pigments, we can use the same adhesive with the same properties but the different colors.
Additives: These are chemical compounds that vary the chemical properties of the adhesives. Fire retardants, emulsifiers, rheology promoters, solvents, dispersants, and plasticizers are considered as an additive in adhesives.