People who often use addition-type liquid silicone raw materials to turn over molds or potting often encounter the phenomenon that the contact surface does not solidify or becomes sticky. When I inquired about it, the reply was that it was caused by platinum catalyst poisoning. For those who have just come into contact with the addition-type liquid silicone, it is not possible. Many people are confused when they hear such professional terms. Let’s give you an in-depth analysis of the reasons why the addition type silica gel platinum catalyst is poisoned and does not solidify.
Definition of poisoning: The phenomenon of decline or loss of catalytic activity of a catalyst due to the action of certain substances is called catalyst poisoning. These substances are called toxins. Poisons are usually impurities brought into the reaction raw materials, or certain impurities in the catalyst itself; reaction products or by-products may also poison the catalyst.
Principle of poisoning: A small amount of impurities contained in the original catalyst are either strongly adsorbed (mostly chemical adsorption) on the active center, or react chemically with the active center and become other substances, thereby poisoning the active center. The severity of "poisoning" is determined by the type and amount of chemicals exposed.
Poisoning substances: For platinum catalysts, catalyst poisons mainly include S, Se, Te, As, Sb, Bi, Zn compounds, halides, etc. Common toxic substances for addition-type platinum silicone include sludge, clay, putty, solder, photosensitive resin, 3D printing (occasionally), etc. The following are common substances that can easily cause platinum catalyst poisoning.
1. Amines and amino compounds: neutralized amines, ethanolamine, N-methylethanolamine, triethanolamine N-dimethylethanolamine, n-butylamine, diethylamine, triethylamine, tetramethyleneethylenediamine (butylamine) Diamine), cyclohexylamine, melamine, dimethylformamide, nitriles, cyanate esters, oximes, nitroso compounds, hydrazine compounds, azo compounds, adiponitrile, methylethyl, nitroso compounds , chelate, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid
2. Sulfur-containing ingredients: dimethyldimethylethanethiol, allylthiourea, etc.
3. Tin-containing ingredients: fatty acid tin salts, organic tin curing agents.
4. Phosphorus-containing ingredients: triphenylphosphine, phosphite, triethyl phosphite.
5. Ingredients containing arsenic, antimony, selenium and tellurium: triphenylarsine, triphenyl stilbene, chlorobenzene carboxymethyl selenide.
6. Residual solvents or monomers: ethanol, methanol, ethyl acetate, vinyl acetate.
7. Primer 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, polyethylene acetate/acrylic.
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