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Abstract  

The accelerated thermal degradation of low-density polyethylene (LDPE) was studied in air at atmospheric pressure and temperatures of 70, 80, 90 and 100C. The changes in elongation at break, traction resistance and density as a result of accelerated thermooxidative degradation were followed. Thermal analysis curves (TG, DTG and DTA) of non-aged and thermally aged LDPE were recorded, and the thermal analysis results were compared with those relating to the variations in the elongation at break, the traction resistance and the density as a consequence of accelerated thermal aging.

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Introduction Low-density polyethylene (LDPE) is a widely used polyolefin due to its excellent properties, such as easy processability, chemical corrosion resistance, electrical insulation properties, and so on. However, easily

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density of the polymer resulting in typical commercial grades including low density (LDPE), linear low density (LLDPE) and high density (HDPE). The temperature at which a specific PE melts is also significantly affected; LDPEs melt at approximately 110 °C

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Modified organophilic montmorillonites/LDPE nanocomposites

Preparation and thermal characterization

Journal of Thermal Analysis and Calorimetry
Authors: Roberta Peila, S. Lengvinaite, G. Malucelli, A. Priola, and S. Ronchetti

Abstract  

In this work a commercially available organophilic Montmorillonite (Cloisite 30B) was modified by interaction with different surfactants, namely dodecylsuccinic anhydride (DSA), octadecylamine (ODA), octadecanoic alcohol (ODOH) and octadecanoic acid (ODAc), in order to increase its basal spacing and to achieve a better dispersibility in LDPE. The morphology of the dispersions was investigated through XRD and TEM analyses. Intercalation phenomena were found for all the systems investigated. The thermal properties of the obtained nanocomposites were studied by means of DSC and TGA measurements. No variation of T m and crystallinity of LDPE was found after the addition of the nanoclays (5 mass/mass%). A significant increase of the air thermal stability of LDPE was achieved in the presence of the modified nanoclays.

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The thermal decompositions of azodicarbamide (AZDICA), 2,2′-azobisisobutyronitrile (AIBN), benzoyl peroxide (Bz2O2), dicumyl peroxide (DICUP) andα, α′-bis(t.-butylperoxy)-m/p-diisopropylbenzene (PEROXIMON F) in binary and ternary mixtures containing low density polyethylene (LDPE) have been studied by means of DSC alone. Binary mixtures including 2% by weight of Bz2O2 or DICUP develop a decomposition heat of 64.2 and 59.1 J/g mixture, respectively. These values are higher than those measured for the decomposition of the pure peroxides. In all the ternary mixtures studied, containing LDPE, a peroxide and an azoderivative, the absolute enthalpic values attributed to the peroxide are lower than those obtained from the LDPE-peroxide mixtures. The enthalpy changes observed have been interpreted on the basis of interactions of the peroxide radicals with the polymer support and with the azo derivative.

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Abstract  

Results obtained on the thermooxidative degradations of LDPE (low-density polyethylene) and NBR (nitrile-butadiene rubber) are presented. The activation energies for the thermooxidations leading to solid products were estimated. For LDPE, the activation energies obtained from non-isothermal data are in satisfactory agreement with those obtained from isothermal data. For NBR, the isothermal activation energy is ≉16% higher than the non-isothermal one. This difference is due to the morphological changes undergone by NBR during its heating at the rather high temperatures at which isothermal measurements were performed.

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Summary A two-step isothermal annealing (TSIA) procedure is described that enables the endothermic peaks of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) and their blends, to be satisfactorily resolved during analysis by differential scanning calorimetry. A modified form of multistep isothermal annealing, the TSIA procedure produces a highly characteristic profile of the blend components by facilitating the segregation of the phases based on branch density. It is proposed that the TSIA procedure may have significant merit in the identification and quantification of the components in an unknown blend as well as increasing the sensitivity in analytical procedures aimed at blend component quantification.

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Abstract

The effect of regeneration conditions on the composition of the gases evolved during the catalytic pyrolysis of low density (LDPE) and high density polyethylene (HDPE) with HUSY and HZSM5 catalysts has been analysed by the TG/FTIR technique. When regenerated HUSY was employed, the evolution of the gases obtained was similar to that with fresh HUSY, indicating that the regeneration treatment did not affect its properties. Nevertheless with HZSM5, as the regeneration temperature was higher, the composition of the gases gradually became more similar to that evolved in the thermal process.

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Journal of Thermal Analysis and Calorimetry
Authors: F. S. M. Sinfrônio, J. C. O. Santos, L. G. Pereira, A. G. Souza, M. M. Conceiçăo, V. J. Fernandes Jr., and V. M. Fonseca
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