The synthesis of nylon-6,6 from adipic acid and hexamethylenediamine typically involves a two-step process: the formation of an intermediate salt nylon salt and the subsequent polycondensation reaction to form the polymer.1. Formation of nylon salt: This step is carried out at room temperature 25C or slightly above, and the reaction time is usually short, ranging from a few minutes to an hour. The reaction is an acid-base reaction between adipic acid and hexamethylenediamine, forming a salt and water as a byproduct.2. Polycondensation reaction: The nylon salt is then heated to initiate the polycondensation reaction, which forms the nylon-6,6 polymer. The optimal temperature for this step is typically between 250C and 285C. The reaction time can vary depending on the desired molecular weight and degree of polymerization, but it generally ranges from 1 to 4 hours.The temperature and reaction time can affect the yield and physical properties of the resulting nylon-6,6 polymer. Higher temperatures and longer reaction times can lead to higher molecular weights and a higher degree of polymerization, which can improve the mechanical properties of the polymer, such as tensile strength and toughness. However, excessively high temperatures or prolonged reaction times can lead to thermal degradation of the polymer, resulting in a decrease in molecular weight and a reduction in the polymer's mechanical properties.In summary, the optimal temperature for the synthesis of nylon-6,6 from adipic acid and hexamethylenediamine is between 250C and 285C, with a reaction time of 1 to 4 hours for the polycondensation step. These variables can affect the yield and physical properties of the polymer, with higher temperatures and longer reaction times generally leading to higher molecular weights and improved mechanical properties, but with the risk of thermal degradation if taken to extremes.