Chemiluminescence from oxidation of polyamide 6,6 II. The effect of metals salts

Chemiluminescence (CL) emission from isothermal and non-isothermal oxidation of polyamide 6,6 in the presence of Co, Ni, Cu and Zn chlorides, alone or combined with KI, demonstrates that copper salts, irrespective of the oxidation number, are the most efficient stabilizing species. They reduce CL emission of the third stage of observed kinetic runs, ascribed to the chain oxidation of polyamide, most efficiently. Cobalt chloride has pro-oxidative rather than a stabilizing action. Synergism has been observed for chlorides of Ni, Zn and Co and for KI. The kinetic analysis of chemiluminescence against temperature was based on two different pathways of initiation: 1. A fast process via either free radicals entrapped in the polymer or terminal amino groups. 2. A slower process involving the free radical chain oxidation of the polyamide. The presence of metal salts combined with KI leads to a reduction of the rate constants of the slower stage by more than two orders of magnitude whilst the rate constants of the faster stage are increased by the presence of metal salts

Morphological and Thermal Properties of Cellulose-Montmorillonite Nanocomposites

Cellulose-layered montmorillonite (MMT) nanocomposites were prepared by precipitation from N-methylmorpholine- N-oxide (NMMO)/water solutions. Two hybrid samples were obtained to investigate the influence of the reaction time on the extent of clay dispersion within the matrix. It was observed that longer contact times are needed to yield nanocomposites with a partially exfoliated morphology. The thermal and thermal oxidative properties of the hybrids, which might be of interest for fire-resistant final products, were investigated by thermogravimetry and chemiluminescence (CL). The nanocomposites exhibited increased degradation temperatures compared to plain cellulose, and the partially exfoliated sample showed the maximum stability. This result was explained in terms of hindered transfer of heat, oxygen, and degraded volatiles due to the homogeneously dispersed clay filler. Kinetic analysis of the decomposition process showed that the degradation of regenerated cellulose and cellulosebased hybrids occurred through a multistep mechanism. Moreover, the presence of nanoclay led to drastic changes in the dependence of the activation energy on the degree of degradation. CL analysis showed that longer permanence in NMMO/water solutions brought about the formation of carbonyl compounds on the polymer backbone. Moreover, MMT increased the rate of dehydration and oxidation of cellulose functional moieties. As a consequence, cellulose was found to be less stable at temperatures lower than 100 °C. Conversely, at higher temperatures, the hindering of oxygen transfer prevailed, determining an increase in thermo-oxidative stabilit

Thermal oxidation and its relation to chemiluminescence from polyolefins and polyamides

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