The synthesis of nylon-6,6 involves the condensation polymerization of adipic acid and hexamethylenediamine. The optimal reaction conditions and yield, as well as purification techniques for improving the purity of the product, are as follows:1. Optimal Reaction Conditions: - Temperature: The reaction is typically carried out at elevated temperatures, around 250-285C. - Pressure: The reaction is performed under atmospheric pressure or slightly above. - Catalyst: A catalyst, such as antimony trioxide, is often used to promote the reaction. - Molar Ratio: A 1:1 molar ratio of adipic acid to hexamethylenediamine is ideal for the formation of nylon-6,6. - Solvent: The reaction is typically performed in a solvent, such as water or an organic solvent like N-methyl-2-pyrrolidone NMP , to facilitate the reaction and control the molecular weight of the polymer.2. Yield: The theoretical yield of nylon-6,6 from adipic acid and hexamethylenediamine is 100%, assuming complete conversion of the monomers. However, in practice, the yield may be lower due to side reactions, incomplete conversion, or loss during processing. Typical yields for industrial processes are around 90-95%.3. Purification Techniques: - Filtration: The crude nylon-6,6 product may contain unreacted monomers, catalysts, or other impurities. Filtration can be used to remove solid impurities. - Washing: Washing the crude product with water or a suitable solvent can help remove residual monomers, catalysts, or other soluble impurities. - Precipitation: The polymer can be precipitated from the reaction mixture by adding a non-solvent, such as methanol or acetone, to the solution. The precipitated nylon-6,6 can then be separated by filtration or centrifugation. - Dialysis: Dialysis can be used to remove low molecular weight impurities, such as unreacted monomers or oligomers, from the polymer solution. - Solvent extraction: Solvent extraction can be used to selectively remove impurities from the crude product based on their solubility in different solvents.By optimizing the reaction conditions and employing suitable purification techniques, it is possible to obtain high-purity nylon-6,6 with a high yield.