FT–IR spectroscopic study on the thermal and thermal oxidative degradation of nylons

Abstract

SynopsisThe effects of heat and oxygen on nylon films were studied by FT-IR spectroscopy. Nylons 6, 66 and nylons containing carbonyl groups in either the diamine or the diacid moiety were prepared. Nylon f i l m s cast on aluminum were studied in an environmental chamber under controlled conditions. The progress of chemical and physical changes was monitored by FT-IR spectroscopy. Thermal energy caused largely an increase in crystallinity due to annealing and also an increase of nonhydrogen-bonded amide groups, which seemed to entail mainly amide groups from the amorphous region. The intensities of IR absorption bands related to the folded structure reduced as soon as heating began. The IR spectra of the carbonyl groups formed by thermal oxidation showed band shapes that indicated that the formed carbonyl groups were of many different origins. The presence of keto groups purposely inserted into the backbone chains increased the rate of oxidation. Pyrolysis of the nylons was also studied to supplement data obtained a t lower temperatures.

Polypyrrole coated nylon lycra fabric as stretchable electrode for supercapacitor applications

“…2 (i)) [25]. Bands at 1640 cm -1 and 1547 cm -1 could be attributed to C=O stretching vibrations (Amide I band) and N-H bending vibrations (Amide II band) [26,27], respectively. The spectra of the coated fabric before and after stretching were characterized by typical features of PPy [28,29].…”

Effects of acid dyes on crystallization and mechanical properties of melt-reprocessed nylon 66

“…It has been reported that the low frequency peak at 1639 cm Ϫ1 within the CAO stretching band is associated with the hydrogenbonded CAO bonds, and the peak at 1643 cm Ϫ1 is assigned to "free" carbonyl bonds. 28,29 The appearance of shoulders between 1650 and 1700 cm Ϫ1 were also interpreted as the formation of different types of carbonyl compounds during the thermal degradation/oxidation of nylon. 29 Accordingly, the observed decrease in the height of the peak at 1639 cm Ϫ1 in the metallized acid dye containing nylon samples indicates the decrease in hydrogen bonding between the amide groups of the nylon chains.…”

Review on the thermo-oxidative degradation of polymers during processing and in service

“…Polyamides containing primary amino end-groups show yellowing almost from the start of oxidation, whereas their molecular weights drop much more slowly [123][124][125][126][127][128][129][130][131][132][133]. Amine end groups can initiate the homolysis of hydroperoxides too, but primarily they condense with aldehydes generated by oxidation to aldimines [134].…”