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aIn this study, the mechanical properties and non-isothermal degradation kinetics of polypropylene (PP), high-density polyethylene (HDPE) with dilauroyl peroxide and their blends in different mixture ratios were investigated. The effects of adding dilauroyl peroxide (0-0.20 wt%) on the mechanical and thermal properties of PP + HDPE blends have been studied. On the other hand, the kinetics of the thermal degradation and thermal oxidative degradation of PP + HDPE (80/20 wt%) blends were studied in different atmospheres, to analyze their thermal stability. The kinetic and thermodynamic parameters such as the activation energy, E a , the pre-exponential factor, A, the reaction order, n, the entropy change, the enthalpy change, and the free energies of activated complex related to PP, HDPE, and blend systems were calculated by means of the several methods on the basis of the single heating rate. A computer program was developed for automatically processing the data to estimate the reaction parameters by using different models. Most appropriate method was determined for each decomposition step according to the least-squares linear regression.

Poly(cyclohexene oxide) (PCHO)/clay nanocomposites were prepared by means ofin situ photoinitiated cationic polymerizationwith initiator moieties immobilized within the silicate galleries of the clay particles. Diphenyliodonium molecules were intercalated via cation exchange process between Cloisite Ca and diphenyliodonium. The polymerization of CHO through the interlayer galleries of the clay can provide a homogenous distribution of the clay layers in the polymer matrix in nanosize and results in the formation of PCHO/clay nanocomposites. The rates of clay loadings were changed to 1%, 3%, and 5% so as to investigate the effect of clay and initiator amount on polymer. X-ray diffraction (XRD) spectroscopy, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) methods were used for the characterization of modified clay and nanocomposite materials. Thermal stability of PCHO/MMT nanocomposites was also studied by both differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

Polypropylene R low density polyethylene (PP R LDPE) blends involving 0, 25, 50, 75 and 100 wt% of PP with dialkyl peroxide (DAP) were prepared by melt blending in a single-screw extruder. The effects of adding dialkyl peroxide on mechanical and thermal properties of PP R LDPE blends have been studied. It was found that at lower concentrations of peroxide (e.g., 0-0.08 wt% of dialkyl peroxide) LDPE component is cross-linked and Polypropylene (PP) is degraded in all compositions of PP R LDPE blends. Mechanical properties (Tensile strength at break, at yield and elongation at break), Melt flow index (MFI), hardness, Scanning Electron Microscope (SEM) and thermal analyses (DSC) of these blends were examined. Because of serious degradation or cross-linking the mechanical properties and the crystallinty (%) of those products were decreased as a result of increasing peroxide content.

Polypropylene‐low density polyethylene (PP‐LDPE) blends involving PP‐LDPE (90/10 wt%.) with (0.06 wt%) dialkyl peroxide (DAP) and different amounts (5, 10, 20 wt%) of calcium carbonate (CaCO3) were prepared by melt‐blending with a single‐screw extruder. The effect of addition of CaCO3 on thermal decomposition process and kinetic parameters, such as activation energy and pre‐exponential factor of PP‐LDPE blend with DAP matrix, was studied. The kinetics of the thermal degradation of composites was investigated by thermogravimetric analysis in dynamic nitrogen atmosphere at different heating rates. TG curves showed that the thermal decomposition of composites occurred in one weight‐loss stage. The apparent activation energies of thermal decomposition for composites, as determined by the Tang method (TM), the Kissinger–Akahira–Sunose method (KAS), the Flynn–Wall–Ozawa method (FWO), and the Coats–Redfern (CR) method were 156.6, 156.0, 159.8, and 167.7 kJ.mol−1 for the thermal decomposition of composite with 5 wt% CaCO3, 191.5, 190.8, 193.1, and 196.8 kJ.mol−1 for the thermal decomposition of composite with 10 wt% CaCO3, and 206.3, 206.1, 207.5, and 203.8 kJ mol−1 for the thermal decomposition of composite with 20 wt% CaCO3, respectively. The most likely decomposition process for weight‐loss stages of composites with CaCO3 content 5 and 10 wt% was an An sigmoidal type. However, the most likely decomposition process for composite with CaCO3 content 20 wt% was an Rn contracted geometry shape type in terms of the CR and master plots results. It was also found that the thermal stability, activation energy, and thermal decomposition process were changed with the increase in the CaCO3 filler weight in composite structure. Copyright © 2009 John Wiley & Sons, Ltd.