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The role of surfactants in castables

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Surfactants are materials that can significantly change the surface tension of a liquid or the interfacial tension between them. Many additives are surfactants. When the refractory castable is mixed, adding a very small amount of surfactant can significantly change the surface energy between the interfaces of the refractory castable and play a role in wetting, emulsifying, dispersing, solubilizing, foaming and lubricating.

The molecule of a surfactant is generally composed of a polar hydrophilic group and a non-polar lipophilic group (hydrocarbon chain portion). According to the charged state in dissolved water, it is divided into two types: ionic and non-ionic. The former is divided into three categories: positive, neutral and negative. Anionic surfactants, such as alkylbenzene sulfonates, dissociate into ions in water, and the groups that act are anions; the cationic surfactants act as cations; and both ions in amphoteric surfactants are kick in. Non-ionic surfactants, such as fatty alcohol polyoxyethylene ethers, do not dissociate into ions in water, are not charged, and do not undergo strong adsorption, and act as oxygen-containing groups.

Among surfactants, water reducers are most commonly used. Water reducing agents are also called plasticizers, which mainly include lignin sulfonates, aromatic sulfonates (that is, coal tar and naphthalene), humates, molasses, NNO and NF. Its working principle is that it has the functions of absorbing and dispersing and lubricating the refractory castable, and can affect the change of its potential, so as to achieve the purpose of reducing water consumption. Non-ionic surfactants, surfactants, cationic surfactants, sodium polyacrylate, silane coupling agent, mechanism of action of surfactants in casting materials, inhibitors, foaming agents and dispersants are also mostly chemical materials, such as oxalic acid , Rosin soap, etc .; Accelerators refer to materials that can accelerate or complete the setting and hardening of materials. Water glass binders use sodium fluorosilicate or portland cement; phosphoric acid and phosphate binders use double salt cement.

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