Adhesive adsorption theory
Time：2012-09-27 16:09:58 Hits：1604
Solid adhesive adsorption as a main reason for the theory of bonding, adsorption theory called bonding. The theory is that: the adhesive force of a major source of bonding system of intermolecular forces, ie van der attraction and hydrogen bonding force. The adhesive and the adherend surface of the adhesive force with the suction force having a same nature. The adhesive molecules and the action process of the adherend surface molecules have two processes: the first stage is a liquid adhesive molecules to the surface diffusion of the adherend by means of the Brownian movement close to each other, so that the two interfaces of the polar group or segment, in this process, the temperature was raised, a contact pressure is applied, are conducive to the strengthening of the Brownian motion and reduce the viscosity of adhesives or the like. The second stage is the generation of adsorption force. When the distance between the adhesive and adherend molecular reaches 10-5Å, the interface between the molecules produced mutual attraction, the distance between the molecules is further reduced to a state of maximum stable.
According to calculations, because the van der Waals force, away from the plane when the two ideal 10Å, and the strength of the gravitational attraction between them of up to 10-1000 mPa; when 3-4Å distance is up to 100-1000Mpa. This value is much more than can reach the strength of the best modern structural adhesives. Therefore, it was considered that when two object contact good, i.e. the adhesive on the bonding interface sufficiently wetted to achieve the desired state of the case, only the role of dispersion force, sufficient to produce a high bonding strength. However, the actual bonding strength with the theoretical calculations vary greatly, this is because the mechanical strength of the solid is a kind of mechanical properties, rather than the molecular properties, and its size depends on the material of each of a local nature, and not equal to the sum of the intermolecular forces. The calculated value is assumed that the two ideal plane close contact, and to ensure that the interface layer between the respective pairs of molecules at the same time destroyed, it is impossible to ensure that the force between the respective pairs of molecules simultaneously.
Polarity of the adhesive is too high, and sometimes seriously impede the conduct of the wetting process and reduce the adhesive force. Intermolecular forces factors provided adhesive force, but it is not the only factor. In some special cases, other factors can also play a leading role.
