Comparison of the properties of clay polymer nanocomposites prepared by montmorillonite modified by silane and by quaternary ammonium salts

• Sodium montmorillonite (Na+-Mt) was modified by 3-aminopropyl triethoxy silane.
• Different silylation times and aminosilane concentrations were applied.
• Mt epoxy nanocomposites with silylated Mt were prepared.
• Mt epoxy nanocomposites with commercial organically modified Mt were prepared.
• Silylated Mt yields higher elastic modulus compared to commercial Mt.

In this work, the silylation of sodium montmorillonite (Na+-Mt, Nanofil 757®) was performed using (3-aminopropyl)triethoxy silane (APTES). Different reaction conditions were used varying the reaction time and the amount of the aminosilane. Epoxy-based nanocomposites were prepared with different amounts of silylated Mt or commercial organically modified Mt intercalated with stearylbenzyldimethyl ammonium chloride (Nanofil 2®) and distearyldimethyl ammonium chloride (Nanofil 8®), respectively. The grafting/intercalation of the aminosilane inside the Mt interlayer spaces was studied by means of Fourier transform infrared (FTIR), X-ray diffraction (XRD), nuclear magnetic resonance (NMR) and thermogravimetric analysis (TGA). After isothermal curing at 90 °C the Mt epoxy nanocomposites were analyzed by means of XRD and dynamic mechanical analysis (DMA). The glass transition temperature of all prepared nanocomposites containing silylated Mt, is slightly higher than that of the neat epoxy (2 to 5 °C). In the presence of 1 to 5 m% of silylated Mt in epoxy matrix the storage modulus increases from about 5 to 15% at 25 °C, respectively, compared to the pristine epoxy matrix, while only 0–4% increase was observed for epoxy nanocomposites with commercial modified Mt.