Effect of the mechanical treatment of alumina on thermal, morphological and dielectric properties of LDPE/Al₂O₃ composites

Abstract

Composites of LDPE filled with different amounts of alumina Al₂O₃ 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 Al₂O₃ 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 Al₂O₃ were compared to those prepared with the neat Al₂O₃. The thermogravimetric (TGA) results showed an enhancement of 55 °C in the thermal stability for the LDPE/Al₂O₃ composition containing 1 wt% of treated Al₂O₃. 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, Al₂O₃ nanoparticles, stearic acid, co-mixing method