Study on the Long-Term Acid Rain Aging Behaviour of Polyamide 6

The long-term acid rain aging behavior of polyamide 6 (PA6) was studied in aqueous solution with pH = 1 at 40°C in comparison with a stabilized sample (Stabilizer: 0.2wt% Irganox 1010, 0.2wt% Irgafos 168, 0.3wt% Tinuvin 770 and 0.3wt% Tinuvin 234). The aging can be described as a succession of three stages. The first one corresponded to the physical absorption of water until equilibrium while the chemical degradation can be neglected resulting in a drop of the mechanical strength and an increase of the toughness of the sample of PA6. The hydrolysis reaction of the amido link of PA6 predominated during the middle and last stage of aging, resulting in a decrease of all the mechanical properties. The reduced viscosity of PA6 decreased monotonically during the whole aging process. The end amine group concentration could not be detected due to its reaction with acid. The carboxylic acid came not only from the carboxylic acid end group produced by the degradation of the sample, but also from the acid rain. The stabilizers didn't have any effect of the anti-acid rain degradation of PA6.