People who use platinum-cured silicone rubber often encounter the phenomenon of not curing or contact surface is not cured sticky, a reply obtained by inquiring is caused by platinum catalyst poisoning, so what does catalyst poisoning mean? The following shares the analysis of the phenomenon of platinum catalyst poisoning.
Poisoning Definition: The phenomenon that the catalytic activity of a catalyst declines or loses due to the action of certain substances is called catalyst poisoning. These substances are called toxic substances. Toxic substances are usually impurities carried in the reaction raw materials, or some impurities of the catalyst itself, in addition the products or by-products produced by the reaction may also poison the catalyst.
Poisoning Principle: A small amount of impurities contained in the catalyst raw materials are either strongly adsorbed on the active center (mostly chemical adsorption), or chemically interact with the active center and become other substances, thereby poisoning the active center. The severity of "poisoning" is determined by the type and quantity of chemicals that you are exposed to.
Toxic Substances: For platinum catalysts, the main catalyst toxic substances are compounds containing S, Se, Te, As, Sb, Bi, Zn and other elements, halides, etc. The following are the common substances that can easily cause platinum catalyst poisoning.
a. Amines and amino compounds: neutralizing amine, ethanolamine, N-methylethanolamine, triethanolamine, N-dimethylethanolamine, n-butylamine, diethylamine, triethylamine, tetramethylene ethylenediamine (butyl Diamine), cyclohexylamine, melamine, dimethylformamide, nitriles, cyanate esters, oximes, nitroso compounds, hydrazine compounds, azo compounds, adiponitrile, methyl ethyl, nitroso , Chelate, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid
b. Sulfur-containing ingredients: ethanethiol acid, allyl thiourea, etc.
c. Tin-containing ingredients: fatty acid tin salt, organic tin curing agent.
d. Phosphorus components: triphenylphosphine, phosphite, triethyl phosphite.
e. Containing arsenic, antimony, selenium, and tellurium components: triphenylarsine, triphenyl symmetry diphenylethylene, chlorobenzyl carboxymethyl selenide.
f. Residual solvents or monomers: ethanol, methanol, ethyl acetate, vinyl acetate.
g. Bottom coating: Clay coating glue with polyethylene acetate or acrylic latex as adhesive, coating glue containing calcium carbonate, natural rubber latex/clay, latex/ethylated starch, styrene/acrylic acid, Polyvinyl acetate, polyvinyl acetate/acrylic acid.