Thermolysis parameter and kinetic research in copolyamide 66 containing triaryl phosphine oxide

Flame-retardant polyamide 66 (FR-PA66) was fabricated with adipic acid hexamethylene salt and bis(4-carboxyphenyl)phenyl phosphine oxide as raw materials. Thermogravimetric (TG) data of flame-retardant FR-PA66 at different heating rates were measured by employing TG analyzer, and analyzed with Flynn-Wall-Ozawa and Coast–Redfer method, respectively. The results show that the flame-retardant properties of triaryl phosphine oxide on FR-PA66 come from the first cleavage of P–C bond and forming of carbonized protective layer. The former reduces the initial thermolysis activation energy of FR-PA66 to 75 kJ/mol. The latter improves the middle and late thermolysis activation energy of FR-PA66 to 190 kJ/mol and 195 kJ/mol, which is higher than that of PA66 for 50 kJ/mol and 46 kJ/mol, respectively. The most probable thermolysis kinetic mechanism function (f(α)) of FR-PA66 in three different stages are showed as following: when the rate of decomposition (α) is lower than 0.1, f α = 1 − α ; when α is between 0.1 and 0.7, f ( α ) = 2 ( 1 − α ) 1 / 2 ; and when α is beyond 0.7, f ( α ) = − [ I n ( 1 − α ) ] − 1 .