Nylon degradation study

We studied the polyamidation of nylon 4,6, and varied the reaction time, reaction temperature, partical size, starting molecular weight, and type of reactor gas. At the same time we looked at the molecular weight broadening and the degradation with colour formation. In order to have good heat and mass transfer the reactions were mainly conducted on fine powder in a fluidized bed reactor and with dry nitrogen as carrier gas. 

It is difficult to find any definitive information that indicates ozone damage as extensive as that suggested in the mri report. The latter identified cotton, nylon, and rayon as particularly susceptible to ozone. The oxidation of cellulose fibers by ozone was the subject of a study in 1952 that showed that dry cotton was not seriously degraded by ambient ozone. In more recent studies, these conclusions were confirmed. The only information available on fibers other than cotton addressed the effect of ozone on modacrylic, acrylic. Nylon 66, and polyester fabrics.The results indicated minimal effects on these fibers. 

In past studies (3), Electron Spin Resonance, ESR, has been used to investigate bond rupture associated with stress-ozone degradation in unsaturated rubbers. It was believed that it might be enlightening to perform similar experiments on plastics ( 5, 8, 10, 11). In the study reported here the combined effects of environment (O3, N02 and S02) and sustained stress on the ultimate properties of Nylon 6 fibers are presented. These agents were found to have a profound effect on strength, toughness and the deformation-bond rupture kinetics. 

Levchik, S. V., Levchik, G. F., Balanovich, A. I., Camino, G., and Costa, L., Mechanistic study of combustion performance and thermal decomposition behaviour of Nylon 6 with added halogen-free fire retardants, Polym. Degrad. Stab., 1996, 54, 217-222. 

One of the more recent studies on cotton, polyester, and nylon (24) demonstrated that cotton was superior to the synthetics in outdoor performance in areas of low air pollution but that its performance was reduced considerably in areas of high air pollution. Specific effects of air pollutants are discussed later under chemical agents causing fiber degradation. 

Several other pyrolytic studies were performed on nylon 6. In one such study [4], the influence of several aliphatic carboxylates on nylon 6 thermal degradation was studied. The carboxylates that were evaluated include sodium butyrate, sodium caproate, sodium a-ethylcaproate, sodium caprylate, sodium laurate, potassium caproate, potassium laurate, and lithium caproate. Small amounts of these aliphatic carboxylates strongly increase the thermal decomposition rate even at 280° C. The effect of aliphatic carboxylates can be explained by the deprotonation of one of the amide groups of the polymer followed by the nucleophilic substitution of a neighboring carbonyl group, in a reaction as shown below ... 

Nylon fibers are used extensively in outdoor textiles and as a result are subject to sunlight, varying temperatures and acid precipitation. The degradation of nylon by light, heat, humidity and air polluted with sulfur dioxide has been widely studied (8-13). However, little data is available on the effect of aqueous acid on nylon in the presence of heat, light and moisture (i.e. acid rain conditions). Therefore, the purpose of this work was to determine the effect of acid rain conditions on nylon. The synergistic effects of aqueous acid, light and heat on nylon were also examined. 

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