one ️⃣  mechanical theory

The surface of an object may appear smooth, but in the microscopic world, it is filled with grooves and pores. Adhesives can penetrate into these uneven areas and, after curing, bond objects together through anchoring, hooking, and wedging.

two ️⃣  Electrostatic theory

When the adhesive comes into contact with the adhered object, a double layer is formed on both sides of the interface, similar to the two plates of a capacitor, thereby generating electrostatic attraction. Experimental results have shown that the bonding work is equal to the instantaneous discharge energy of this capacitor.

three ️⃣  diffusion theory

The molecules of the adhesive and the adherend diffuse with each other, causing large molecules to entangle or dissolve at the interface, resulting in the disappearance of the interface and the formation of transition zones, thus forming a strong bond after curing. Diffusion theory is also known as molecular permeation theory.

four ️⃣  adsorption theory

The adsorption force between adhesive molecules and the adhered material is the main reason for bonding, which includes physical adsorption and chemical adsorption. Physical adsorption is a common cause of adhesive bonding.

five ️⃣  chemical bonding theory

The bonding effect is due to the formation of chemical bonds between adhesive molecules and the surface of the object being bonded through chemical reactions. The chemical bond is 1~2 orders of magnitude higher than the intermolecular force. If the chemical bond can be formed, the bonding with higher strength and aging resistance will be obtained. It is very instructive for bonding wood and other materials.

📝  Formula design of synthetic adhesive

one ️⃣  Select base material

Select appropriate base materials or synthesize new polymers based on the purpose and main functional indicators of the adhesive.

two ️⃣  Choose curing agent and accelerator

Select appropriate curing agents or initiators, as well as corresponding accelerators, based on the cross-linking reaction mechanism of the base material.

three ️⃣  Determine the formula plan

Determine the principle formula scheme based on the reaction stoichiometry relationship.

four ️⃣  formula experiments

Conduct formulation experiments with the main functional indicators of the adhesive as the objective function.

💪  Ways to improve the performance of adhesives

Improve bonding strength

Improve heat resistance

Improve cold resistance

Improve solvent resistance

Improve acid and alkali resistance

Improve flame retardancy

Improve water resistance

Improve aging resistance

Through these methods, the performance of adhesives can be effectively improved to meet various application needs.