Accelerated aging of nylon 66 and Kevlar 29 in elevated temperature, elevated humidity, smog, and ozone

Abstract

Accelerated aging of Nylon 66 and Kevlar 29 yarns was carried out in humid air, smog, and ozone to establish aging trends in these environments. Tensile strengths of nylon yarn aged in a humid environment (50% RH at ambient temperature) for six months degraded from 40% at 1 10 O C to 85% at 150 OC. Kevlar yarns in the same test lost from 10% (130 "C) to 32% (170 "C) of their strength. Based on these data, the estimated energy of activation for the nylon degradation is 18 kcal/mol and for the Kevlar degradation is 13 kcal/mol. Nylon exposed to smog for six months lost -63% of its tensUe strength compared to -7% loss in ozone. Kevlar strength loss was -27% for smog exposure and insignificant for ozone exposure. No trend between oxygen depletion or carbon dioxide generation and strength loss was apparent in the gas analyses. Infrared spectrophotometry did not show changes in materials degraded at significant levels (40 % ). Preliminary nondestructive chemiluminescence studies indicate a linear relationship between thermally induced chemiluminescence and tensile strength.

Aging characteristics of glass fiber‐reinforced polyamide in hot water and air

“…A first‐order kinetic analysis of the declining stress‐at‐break values revealed a linear Arrhenius behavior resulting in activation energy of 165 kJ/mol in the temperature range from 95°C to 135°C. For nylon yarns exposed to humid air (10 and 50% RH ) at elevated temperatures (110°C, 130°C, and 150°C), the literature reports approximately 75 kJ/mol . This deviance may result from different stabilizer packages, reinforcing filler materials, specimen surface‐to‐volume ratios, or different environmental conditions.…”

“…For the early stages of degradation, activation energy of 15 kJ/mol was reported for water exposed PA66 based on infrared spectroscopic data . For mechanical degradation, however, activation energy of about 75 kJ/mol was deduced . For glass fiber‐reinforced polyamide 66 grades, no activation energies are described in the literature.…”

Accelerated Aging, Photochemical and Thermal Aspects

“…Numerous examples of the limitations in particular measurements can be cited. For example, Mead et al (1982) concluded that "infrared examination of aged nylon yarns with various degrees of degradation showed only slight differences for the most severely degraded samples when compared to controls"; the authors found only slight differences in the infrared absorption spectra of samples that had lost as much as 40% in tensile strength. In another situation, because the discoloration of many polymers is often bleached by the same light source that is used to initiate deterioration, Bendaikha and Decker (1984) point out that "discoloration, although an important parameter in testing the light sensitivity of a polymer, may actually reflect quite imperfectly the extent of photodegradation occurring."…”

The characterization of microenvironments and the degradation of archival records :

“…Both Hudson, et.al, and Jellinek, et.al. carried out experiments at various temperatures and were able to obtain activation energies. Another group of workers (63) were actually concerned with accelerated aging of nylon and Kevlar by smog and ozone, using tensile strength as the physical measure of degradation. It was found that smog seriously degraded the tensile strength, but ozone did not.…”