Binding Mechanisms of Refractory Binding Agents

Different refractory binding agents have different chemical properties and different binding mechanism. There are six common typical binding mechanisms. In general, one binding agent has a specific binding mechanism, but sometimes several mechanisms may coexist. This is very important for material design. Sometimes some specific requirements can be achieved by making use of these binding mechanisms.

(1) Hydration binding

Hydration binding is formed through the hydration reaction between binding agents and water at room temperature. For example, cement is bound through the binding hydration mechanism. 

(2) Chemical binding 

Chemical binding is formed through the reaction between the binding agent and coagulant or the binding agent and the refractory at room temperature or when heated. For example, the binding agent sodium silicate (water glass) can react with the coagulant sodium fluosilicate and generate SiO2:nH2O. Siloxane (Si-O-Si) network structure can be formed after dehydration, resulting in a stronger binding.

(3) Polycondensation binding 

Polycondensation binding is formed by forming a network-like structure through the polycondensation of the binding agent by adding a catalyst or a crosslinking agent. For example, novolac resin can form polycondensation binding through a crosslinking reaction with Methylene Tetramine under heating conditions. 

(4) Ceramic binding (sintering binding)

Ceramic binding (sintering binding) is formed through solid - liquid reactions at low temperature by adding auxiliaries or metal powders that can reduce the sintering temperature to reduce the liquid phase forming temperature. 

(5) Adhesion binding

Adhesion binding is formed through one or several physical actions as follows: 

a. Adsorption

It includes physical adsorption and chemical adsorption. The binding is formed by the van der Waals force between molecules.

b. Diffusion

The mutual diffusion of molecules of binding agents and refractories forms a diffusion layer in the interface and thereby forms a strong binding. 

c. Electrostatic interactions

There are electric double layers in the interface of the binding agent and refractories. The electrostatic attraction of the electric double layers forms a strong binding. 

(6) Cohesion binding

   Cohesion binding is formed through the cohesion of binder agents by adding coagulants.