Preparation and characterization of poly(vinylalcohol)/modified bentonite nanocomposites

Abstract

This study describes an effective way for the preparation of well-dispersed poly(vinylalcohol) (PVA)/bentonite and poly(vinylalcohol)/modified bentonite nanocomposites with improved thermal properties. Nanocomposites were synthesized by effectively dispersing the inorganic nanolayers of bentonite in PVA matrix via the solution intercalation method. Bentonite was calcinated at 150 and 650 degrees C and modified with 3-aminopropyltrimethoxysilane (3-APT), dimethylsulfoxide (DMSO) and methanol (MeOH). The surface areas of bentonite and modified bentonite samples were measured by BET surface analyzer. In order to determine thermal stabilities of PVA and its nanocomposites, it was used thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The interactions between polymer, PVA, and filling material, bentonite were determined using Fourier transform infrared spectroscopy attenuated total reflectance (FTIR-ATR). The dispersion and exfoliation of the clay layers in PVA matrix were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The contact angles of PVA and its nanocomposites were determined for nanocomposites by sessile drop method. The activation energies were calculated using the Kissinger method. XRD and TEM results showed that bentonite layers were dispersed in nanoscale and homogenously in PVA matrix. Microscopic and XRD techniques revealed highly organized regions. Clay content up to 5 wt.% led to nanocomposites with high degree of exfoliation. Thermogravimetric analysis indicated that introduction of clay to the polymer network resulted in an increase in thermal stability. Activation energy values at both stages for PVA/bentonite nanocomposite were higher than those of pure PVA, indicating that addition of bentonite particles improves thermal stability of PVA.