Cohesion (chemistry)

As cohesion ( to Latin: cohaesum, past participle of: cohaerere = " related " ) is called in physics and chemistry, the binding forces between atoms and between molecules within a substance. The forces ensure its cohesion. They act in liquids or in solids and lead to the surfaces of a substance to the surface tension. The adhesion contrast, is based on binding forces between two different phases.

Cohesive energy

The simplest way of plastic deformation is the removal of the particle. The energy that is required to remove a particle from an infinite ideal crystal, is the cohesive energy: where N is the number of particles in the system and the interaction energy between two particles i and j in gross neglect of many-body terms.

Causes

The cohesion is caused by the following interactions:

• By chemical bonds within the chemical compounds
• By intermolecular forces such as van der Waals interactions and hydrogen bonds
• By mechanical entanglement of filamentous macromolecules or entanglement of fibrous materials.

Adhesives

In adhesives cohesion refers to the forces which effect the cohesion of the adhesive. This cohesion forces are responsible for one of the strength ( viscosity) and flow properties (rheology ) of the uncured adhesive for processing and the other for the strength of the cured adhesive in its stress. The cohesive forces in an adhesive are described by characteristics such as modulus, elongation, temperature resistance or Shore hardness.