The polyamide nylon-66 is formed from
COOH(CH2)4COOH + NH2(CH2)6NH2
COOH(CH2)COOH + NH2(CH2)NH2
COOH(CH2)4COOH + NHC6H4 NH2(P)
COOHC6H4COOH(P) + NH2(CH2)6NH2
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