Basics of the Bonding Process 120

absorption

A form of adhesive bonding involving the attraction between the molecules of an adhesive and a surface material.

adhesion promoter

A material that helps the adhesive bond to a surface. Adhesion promoters are applied to the surface before the adhesive.

adhesive bonding

The process of binding materials together using any number of adhesive substances. Paste, glue, and tape are examples of common adhesives, while structural adhesives are used for most industrial applications.

carrier material

A material that is mixed with the adhesive and that helps the adhesive wet a surface. Most carriers are either water or a solvent.

chemical bonding

A form of adhesive bonding involving a reaction that results in covalent bonds between the molecules of the adhesive and the surface material.

chemical reaction

A process in which one or more substances are changed into another substance. During a chemical reaction, the physical structure of a substance will alter in some way.

chemisorption

Another term for chemical bonding. The term "chemisorption" is used to emphasize the need for close contact between the adhesive and the substrate.

cooling

The process in which an adhesive physically changes from a liquid to a solid. Cooling occurs when there is a drop in temperature in the adhesive.

covalent bond

A type of atomic bond that occurs when two atoms share electrons. Covalent bonds are relatively strong.

creep

The deformation of a material that occurs over time due to the presence of a constant load.

cross-link

To form primary bonds between polymer molecules.

cross-linking

The development of primary bonds that form between polymer molecules.

curing

The process in which an adhesive undergoes a chemical reaction and becomes a solid. Curing requires pressure, heat, UV light, water, or some other means to initiate the chemical reaction and form the bonded joint.

curing agent

A chemical that induces curing within an adhesive.

diffuse

To transfer material from one object to another due to the migration of atoms. During the drying of some adhesives, the carrier material diffuses into the surface.

drying

A form of adhesive solidification in which either solvent or water evaporates in the air or dissolves into the surface.

elastic

Able to return to its original shape after deformation.

elasticity

The measure of a material's ability to return to its original shape after it has been stretched or deformed.

hot melt

A type of adhesive that requires heat for application and strengthens as it solidifies.

mechanical bonding

A form of adhesive bonding during which adhesive material physically locks into the crevices of the surface.

mer

A basic molecular unit that consists of a collection of atoms. Polymer molecules contain thousands of repeating mers bonded in a long chain.

polymer

A very large molecule consisting of repeating atomic units, or mers. Almost all adhesive materials consist of polymers.

primary bond

A bond that forms between atoms and that involves the exchanging or sharing of electrons.

primer

A liquid material that is used to coat a surface before the adhesive is applied. Primers improve surface conditions and allow for stronger adhesive bonds.

solidify

To change from a liquid to a solid. The bond between surfaces strengthens as the adhesive solidifies.

substrate

The surface material upon which an adhesive is applied to form a bond or joint.

surface

The section of a material to which the adhesive is applied.

synthetic adhesive

A chemically manufactured adhesive derived from either thermoplastics or thermosets. Synthetic adhesives are commonly used in industrial settings.

viscoelastic

Having both viscous and elastic qualities. Adhesives are viscoelastic materials, combining the characteristics of both liquids and solids.

viscosity

A fluid's resistance to flow. The higher the viscosity, the greater a liquid's ability to resist flow.

viscous

Resistant to flow. A liquid that is more viscous is less likely to flow.

volatile organic compound

VOC. A chemical that releases vapors that are harmful to a person's health and the environment. Solvents are used less often as carrier materials for adhesives because they release VOCs.

wetting

The spreading of an adhesive over a surface. Proper wetting occurs when the adhesive fills all crevices and irregularities of the surface.

wetting agent

A material that helps the adhesive spread across the surface. Wetting agents are applied to the surface before the adhesive.