The optimal temperature and reaction time for the synthesis of nylon-6,6 from adipic acid and hexamethylenediamine can vary depending on the specific process used. However, a common temperature range for this reaction is between 250-285C. The reaction time can range from a few minutes to several hours, depending on the desired molecular weight and degree of polymerization. It is important to note that the reaction conditions should be carefully controlled to minimize side reactions and achieve the desired properties of the nylon-6,6 polymer.