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• Time of issue:2021-07-14
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(Summary description)Between polymers, polymers and non-metals or metals, metal-to-metal and metal-to-non-metal bonding, there are problems of interface bonding between polymer base materials and different materials. Adhesive bonding is a kind of technology with strong comprehensiveness and complicated influencing factors. The existing bonding theories all explain their principles from a certain aspect, so there is no comprehensive and unique theory so far.

Adsorption theory

People regard the adsorption of solids to adhesives as the main reason for bonding, which is called the adsorption theory of bonding. The theory believes that the main source of adhesive force is the molecular force of the adhesive system, that is, Van der’s gravitation and hydrogen bonding force. When the distance between the adhesive and the adherend molecules reaches 10-5Å, the interface molecules generate mutual attraction, which further shortens the distance between the molecules to the maximum stable state.

According to calculations, due to the van der Waals force, when the distance between two ideal planes is 10Å, the gravitational strength between them can reach 10-1000MPa; when the distance is 3-4Å, it can reach 100-1000MPa. This value far exceeds the strength that can be achieved by the best modern structural adhesives. Therefore, some people think that as long as the two objects are in good contact, that is, the adhesive fully wets the bonding interface, the calculated value is to assume that the two ideal planes are in close contact, and to ensure that the interaction between the pairs of molecules on the interface layer is destroyed at the same time At this time, it is impossible to ensure that the forces between the pairs of molecules occur at the same time.

The polarity of the adhesive is too high, and sometimes it will seriously hinder the wetting process and reduce the adhesion. The intermolecular force is a factor that provides adhesion, but it is not the only factor. In some special cases, other factors can also play a leading role.