This study aims to develop poly(vinyl chloride) (PVC) composites prepared by melt mixing by using a combination of talc and calcined kaolin as filler in order to improve the disadvantages of rigid PVC, which is widely used in industry, such as poor mechanical properties and low thermal stability. In addition, PVC/talc and PVC/calcined kaolin composites were also examined for comparison. The calcined kaolin is modified with urea to increase the surface area (chemical treatment), while the surface of both fillers is coated with stearic acid for good compatibility with PVC (mechanical treatment). Scanning electron microscopy micrographs showed homogeneous distribution of mechanically processed fillers. Attenuated total reflectance-Fourier-transform infrared spectroscopy analysis revealed successful coating of the fillers with stearic acid. Also, new bands were detected in the spectrum of urea-treated calcined kaolin, showing an effective chemical treatment. It has been observed that the treatment of fillers improves the mechanical properties of PVC. Thermogravimetric results showed that delaminated calcined kaolin increased the thermal stability of PVC composites. The results of this study proved that binary filler composites combine good properties of both (synergistic effect) and good filler dispersion can be obtained by using stearic acid and urea.

Composites of LDPE filled with different amounts of alumina Al 2 O 3 were prepared using co-mixing technique and melt-mixing. This technique, which is easy, non-toxic and inexpensive, has been successfully used in our laboratory for different polyolefins/ metal oxides nanocomposites elaboration. Samples containing 0.5, 1 and 2 wt% of alumina, were prepared by melt-mixing at 190°C without any chemical treatment or coupling agent. The effect of alumina treatment was studied. The Al 2 O 3 was first co-mixed with the stearic acid then added to the polymer. The stearic acid melts at 70°C, thus ensuring the dispersion of the covered filler particles into the polymeric matrix, which leads to better experimental results. The morphological characterization was carried out by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thermal properties were investigated by thermogravimetric analysis (TGA). The electrical conductivity was also studied. The microstructure-properties relationships were also investigated. The composites prepared with the co-mixed Al 2 O 3 were compared to those prepared with the neat Al 2 O 3. The thermogravimetric (TGA) results showed an enhancement of 55°C in the thermal stability for the LDPE/Al 2 O 3 composition containing 1 wt% of treated Al 2 O 3. The electrical conductivity results showed also an optimum value of 6.6.10-7 Ù-1 cm-1 for the same composition. KEYWORDS Composites, LDPE, Al 2 O 3 nanoparticles, stearic acid, co-mixing method.

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Poly (vinylidene fluoride) (PVDF)-untreated clay nanocomposites were successfully prepared using an innovative one-step reactive melt extrusion process. Through specific temperature and shear conditions, the chemical reactions took place between the polymer matrix, the inorganic clay particles, and three main reactive agents: an organic peroxide, sulfur, and a specific activator led finally to the PVDF-clay nanocomposites. The materials were formulated with various amounts of clay in order to identify the best conditions, enabling to obtain the optimal particle exfoliation in the polymer matrix at the nanometric scale. The microstructure and nanostructure modifications were characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and wide-and small-angle X-ray scattering (WAXS and SAXS). The relationship between nanostructure and mechanical behavior was investigated by tensile experiments, impact tests, and microhardness measurements. The FTIR results suggest that there is a chemical interaction between the clay and the polymer. Furthermore, the WAXS study shows that no intercalation step takes place in any composition. In addition to this, the sample with 2.5 wt.% clay could present a total exfoliation of the clay particles. The PVDF matrix is found to be exclusively of the α-form in all compositions. The final microhardness slightly increases with both nanoclay content and degree of crystallinity.