Effect of Nanoclay Surface Modifier Chemical Reactivity on Morphology and Rheological Properties of PP/PA6 Blend Nanocomposite

Abstract

Abstract An attempt was made to explore the role of nanoclay surface modifier chemical reactivity on the morphology and the rheological properties of a polypropylene/polyamide6 (PP/PA6 75/25) nanocomposite blend. The Na-MMT surface was modified with two types of cations; a) diamine cation (D-Clay), and b) a combination of diamine and quaternary alkylammonium cations (A-Clay) via cation exchange reaction. The nanocomposites samples compatibilized with PP-g-MA were prepared by melt compounding in an internal mixer. The XRD patterns indicated the intercalated/exfoliated microstructure for both nanocomposite samples. The SEM results showed a significant decreases in the PA6 droplet size, from 3.2 μm of the simple blend to the 0.4 μm in the D-Clay containing sample. Moreover, in the sample containing A-Clay the average droplet size was found to be 1 μm. The D-Clay containing sample showed the rheological properties similar to a simple blend in high frequencies with a nonterminal behavior in low frequencies storage modulus. This was explained by locating of D-Clay layers in the interphase and hence, significantly reducing the effective interfacial tension, α/R. In contrast, the sample containing A-Clay showed an increased complex viscosity and storage modulus within a range of frequencies, which was attributed to presence of a large amount of A-Clay layers in the PP matrix. These types of nanoclay partitioning were explained by the possibility of chemical reaction between amine group of nanoclay surface modifier and maleic group of PP-g-MA compatibilizer or in-situ formed block copolymer. Consequently, the D-Clay layers bounded with PP-g-MA is preferentially located in the interphase, while, the non reactive nanoclay layers (containing alkylammonium cations) is dispersed in the PP matrix by assistance of PP-g-MA. These findings were also evidenced by TEM micrograph of both nanocomposite samples.