Nylon thermal degradation

Jha, A. and Bhowmick, A.K., Thermal degradation and ageing behaviour of novel thermoplastic elastomeric nylon-6/acrylate rubber reactive blends, Polym. Degrad. Stab., 62, 575, 1998. 

The Molding Area in Injection Molding (a) Discuss the dependence of each of the curves making up the molding area in Fig. 13.6 on polymer parameters such as Tg, Tm, m(T), n, k, m(P), and Tm(P), and thermal degradation, (b) Apply the preceding ideas to three polymers—PVC, nylon, and HDPE—whose properties appear in Appendix A. 

For nylon-6,10 the smallest cyclooligomer contains 18 atoms in a ring. However, for nylons prepared from amino-acids, much smaller rings are possible. Nylon-6 at 270°C contains about 8 wt. % of caprolactam, the cyclic monomer [81]. Nylon-4 degrades thermally to form the very stable cyclic monomer, pyrrolidone, and the attempted preparation of nylon-4 at conventional high temperatures produces very little polymer [86]. 

The acetylation of the end groups of nylon 6 diminishes the thermal degradation at around 250° C, which suggests that end groups play an important role in this reaction [20, 21], assumed to have a radicalic bite back type mechanism. 

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 ... 

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