Comparative Study of Thermal Behavior of Hdpe/Clay Nanocomposites Prepared with Modified Montmorillonite with Two Functional Organic Agents

Comparative study of thermal behavior of HDPE/clay nanocomposites prepared with modified montmorillonite with two functional organic agents

Verónica Carranza*^1,3, Renato Godoy¹, Eduardo Figueiredo¹, Henrique Perez², Lugão²,  Reinaldo Giudici³

¹Orbys High Performance in Materials - São Paulo, Brazil

²Institute of Nuclear Researches - São Paulo, Brazil

³Chemical Engineering Department of São Paulo University, São Paulo, Brazil

*Email: mvco@usp.br

 

Abstract -

Nanocomposites are the focus for materials engineers to overcome the limitations of traditional micrometer-scale polymer composites. In particular, the field of nanocomposites based on organically modified clays. Thus, the addition of clay, especially montmorillonite in a polymer matrix can have significant influences on the properties of this matrix. For example, increasing of thermal stability of polymer/clay nanocomposites, strength and heat resistance, decreasing gas permeability and increasing biodegradability of biodegradable polymers. The potential of these property improvements usually depend on the degree of delamination and dispersion of the clay in the polymer matrix, which depends on a combination of the proper chemical treatment and optimized processing. Polymer/clay nanocomposites have been successfully used in several kinds of polar polymers. However, for polymers with low polarity, such as polyolefins, the current results are not satisfactory due to the low compatibility between the clay and the polyolefins . In this way, the focus of this study was to evaluate the effect of two kind of modified montmorillonite on the structure and thermal properties of new nanocomposites based in high density polyethylene (HDPE). The two HDPE/modified montmorillonite nanocomposites were prepared by direct melt-mixing procedure using a twin-screw extruder. The modified montmorillonite with a quaternary ammonium salt was used with 5, 7,5 and 20 wt% to prepare the first nanocomposite. The second one was prepared with 7,5 wt% of modified montmorillonite with amino functional alkoxysilane. Changes in the surface of montmorillonite and the dispersion of modified clays in the polymer matrix were evaluated using X-ray diffraction (XRD). The thermal behavior of the clay and nanocomposites were analysed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The XRD results show that almost complete exfoliation of the silicate layers took place and nanocomposite structure was obtained for all new materials. The thermal behavior of the PE/clay nanocomposites can be improved in the case of use 7,5wt% of modified montmorillonite with amino functional alkoxysilane.