Polyethylene/bentonite nanocomposites for packaging applications

LEANDRO N. LUDUEÑA; MATIAS LANFRANCONI; ROMINA OLLIER; VERA A. ALVAREZ

Rio de Janeiro

Conferencia; XV International Clay Conference ICC 2013; 2013

Polyethylene (PE) is one of the most widely used polymers, which exhibits an interesting combination of several useful properties, such us, light weight, low cost, high chemical resistance, low dielectric constant and good processability (Zhao et al., 2005). However, due to its inherent chemical nature, PE has not enough stiffness and other relevant properties required for several applications. Polymer/clay nanocomposites have generated considerable interests in the past decade because adding just a tiny amount of clay to the polymer matrix could produce a dramatic enhancement in physical, thermal, and mechanical properties (Alexandre and Dubois, 2000). Nevertheless, PE and clays are incompatible in nature. There are different ways of improving the compatibility between PE and clays, but the most popular method consists on converting these hydrophilic silicates to organophilic ones by the replacement of original cations by positively charged surfactants such as alkyl ammonium or phosphonium cations with long alkyl chains. Generally, there are two mainly ways to make a nanocomposite; one is the in situ polymerization and the other one is melt blending being the second one favored in the industry (Zhang et al., 2005). In this work, high density polyethylene (PE) based nanocomposites with different loadings (between 0 and 5 wt. %) of organically modified bentonites were prepared by melt blending and their properties were investigated. First, the neat bentonite was modified by cation exchange reactions with ammonium (octadecyl ammonium chloride and dodecyl ammonium chloride) and phosphonium (tributyl octadecyl phosphomium bromide) quaternary salts. All the modifications were optimized, in terms of process conditions, and then, the obtained clays were incorporated into polyethylene matrix The structure of PE/organoclay nanocomposites was investigated by X-Ray Diffraction (XRD) in order to assess the kind of nanocomposite (intercalated or exfoliated) and thermogravimetric analysis (TGA) in order to establish the thermal stability and the real clay content. In addition, thermal properties, such us, crystallinity degree and melting point (Tm) were determined by means of Dynamic Scanning Calorimetry (DSC) and tensile properties were determined by using a universal testing machine. The effect of clay content and clay modification on each parameter were studied and analyzed and all results were used to estimate the matrix - organoclay compatibility. This work was performed under the project FSNano004: ?Development of modified nanoclays and innovative products from national clays?.