Preparation of siloxane-modified tetraglycidyl epoxy - Clay nanocomposites - Its thermal and morphological properties

The organic-inorganic hybrid involving hydroxyl-terminated polydimethylsiloxane (HTPDMS)-modified epoxy, filled with organo-modified flurohectorite clay of various percentages (1-5 wt%) were prepared via in situ polymerization using g-amino propyltriethoxysilane as cross-linking agent in the presence of dibutyltindilaurate catalyst. The reactions involved during the curing process between epoxy and siloxane were confirmed by FT-IR. The results of differential scanning calorimetry and dynamic mechanical analysis show that the glass transition temperatures of the clay-filled hybrid epoxy systems are lower than that of neat epoxy. The data obtained from the thermal studies indicated that improved thermal stability was due to the incorporation of nanoclay into siloxane-modified epoxy hybrid systems. The morphologies of the siloxane containing epoxy-clay hybrid systems show heterogeneous character, due to the partial incompatibility of HTPDMS. Scanning electron microscopy indicates the phase separation, induced by the polymerization, occurs in the HTPDMS-modified epoxy hybrids to yield spherical particles of siloxane-rich phase, which are uniformly dispersed in the continuous epoxy matrix. Microstructures of nanocomposites were ascertained from X-ray diffraction (XRD) and transmission electron microscopy. The formation of exfoliated structure of organoclay was confirmed from the XRD pattern and shows interlayer spacing between 3.42 and 8.50Å . Hybrid epoxy nanocomposites containing higher percentage composition of organo-modified flurohectorite clay contents (up to 5 wt%) display more pronounced improvements in thermal properties and moisture resistance than corresponding unmodified epoxy matrices.