Polyurethane Catalysts – Organometallic Catalysts

2021-12-03   Pageview:360

In polyurethane elastomers and adhesives, coatings, sealants, waterproof coatings, paving materials and other formulations, dibutyltin laurate (DY-12) and other organometallic catalysts are most commonly used, it is very effective in promoting the isocyanate group and hydroxyl reflection, but in the formula with moisture on the reaction between water and isocyanate also has a certain accelerating effect; in the plastic runway and other formulations can be used in organolead and other special catalysts.

Organometallic compounds include carboxylic acid salts, metal alkyl compounds, etc. The metal elements contained are mainly tin, potassium, lead, mercury, zinc, etc. The most commonly used are organotin compounds.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Cathodic inhibition type corrosion inhibitor: zinc sulfate, calcium bicarbonate, phosphate, etc. belong to this type of corrosion inhibitor. They are “safe corrosion inhibitors” as opposed to oxide film-type corrosion inhibitors. Insufficient dosage will not aggravate corrosion. The corrosion inhibition efficiency of these types of corrosion inhibitors is not very high, and they often need to be combined with other corrosion inhibitors in practical applications. Used to enhance the corrosion inhibition effect. They can be used in many forms.

Mixed inhibition type corrosion inhibitor: Most of this type of corrosion inhibitor is organic. Their precipitation film is formed by the interaction between the reactive groups on the corrosion inhibitor molecules and the metal ions generated during the corrosion process. Certain complexing agents containing sulfur, oxygen, and nitrogen atom groups can react with metal ions. A film of insoluble complexes is formed on the metal surface, and at the same time the electrochemical process of the anode and the anode is blocked.

There are also some corrosion inhibitors first through adsorption, and then further polymerize on the metal surface to form a precipitation protective film.

Metal cationic sacrificial pigments, such as zinc powder, wax over emulsion paint initially function as cathodic protection of steel, and then the corrosion products on the surface of the coating play a sealing role. Zinc powder must reach 85% to 95% of the entire solid content to provide the necessary conductivity. An electrochemical cell is built so that steel becomes a cathode on the basis of a sacrificial zinc anode. The use of zinc phosphosilicate to replace part of the zinc pigment can improve the protective and sealing properties of the coating and the sealing properties of the micropores. Zinc powder is divided into spherical shape and flake shape.

Organic compounds are also known as adsorption film type. This type of corrosion inhibitor has good adsorption to the metal surface in the corrosive medium. They are adsorbed on the metal surface to prevent the medium from contacting the metal and prevent corrosion. The molecules of this type of corrosion inhibitor are often composed of polar groups and non-polar groups. The influence of molecular structure on adsorption depends first on the properties of polar groups and non-polar groups. Polar groups contain elements such as oxygen, nitrogen, phosphorus, and sulfur with high electronegativity. The main components of non-polar groups are carbon and oxygen. Among them, the polar group is hydrophilic and can be adsorbed on the active site or the entire surface of the metal surface. The non-polar group is hydrophobic or lipophilic, and the hydrophobic group acts as an isolation to separate the metal surface from the corrosive medium.

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