Mechanism of glycolysis of nylon 6,6 and its model compound by ethylene glycol

The degradation mechanism of nylon 6,6 and its model compound hexamethylenebis(hexamide) (HMHA) by ethylene glycol (EG) was studied in detail. Glycolysis of both model compound and nylon 6,6 was carried out with stoichiometric excess of EG at high temperature (250 and 275 °C, respectively) in an autoclave reactor as a closed system. Samples were collected at predetermined intervals and characterized by FT-IR, GC-MS, and GPC. FT-IR studies of model compound glycolysis showed no significant increase in the ester band after 11 h indicating that the glycolysis reaction may have reached equilibrium. GC-MS data revealed the presence of ester as well as unreacted model compound. GC-MS data for nylon 6,6 revealed the presence of compounds having β-hydroxyethylester group, bis(β-hydroxyethyl)adipate, and δ-valerolactone as the degradation products. From GPC data, as the glycolysis time of nylon 6,6 increased, both the number average and weight average molecular weights decreased indicating that the main chain of nylon 6,6 was broken into low molecular weight compounds during glycolysis.