Photodegradation of nylon 66. I. Phototendering by TiO₂

Abstract

synopsisThe mechanism by which TiOz exerts a phototendering effect on nylon 66 photodegradation has not been previously explained. To aid in the elucidation of this mechanism, the wavelength dependence curves of photodegradation of nylon 66 both with and without Ti02 have been accurately determined. These dat,a, in conjunction with reflectance and phosphorescence measurements, indicate that the phototendering effect of TiOz proceeds by a chemical rather than an energy transfer mechanism.

Photophysical processes in poly(hexamethylene adipamide)–acid dye complexes: Energetics of nylon 66 phototendering

“…An excitation maximum at 290 nm and a broad structureless emission with a maximum centered at 400 nm are observed. These excitation and emission wavelengths correspond to the values reported by Dearman et al 33 and Taylor et al 34 for nylon 66 films and yarns. The nylon luminescence decays exponentially with a mean lifetime of 1.9 sec at liquid nitrogen temperature, 77°K.…”

“…7), which agrees with the spectra published by Taylor et a1. 34 The 290 nm excitation is the nylon electronic transition, and the weak 365 nm excitation is attributed to the titanium dioxide. Maximum emission occurs at 400 nm upon excitation of the dull nylon with 290 nm energy and at 480 nm upon exciting the dull nylon with 365 nm radiation.…”

Progress in the Area of Degradation and Stabilization of Nylon 66

“…Taylor, Tincher, and Hemmer [29] studied photooxidation of nylon 66 in the absence and presence of titanium dioxide. They observed that the phototendering effect of titanium dioxide proceeded by a chemical, rather than energy, transfer mechanism.…”

NMR Analysis of UV- and Heat-Aged Nylon-6,6

“…The above reaction mechanisms are consistent with those proposed by earlier workers. [12][13][14][15][16][17][18] Amide bond scission (a bond between the carbonyl and amide nitrogen) has been proposed by some previous investigators. This would result in the formation of amine end groups, which is clearly contradictory to our data in Table 2 for both UV degradation and heat aging.…”