Thermooxidative degradation of LDPE nanocomposites: Effect of surface treatments of fumed silica and boehmite alumina

Fumed silica (FS) and synthetic boehmite alumina (BA) nanofillers with and without surface treatments were incorporated in 5 wt. % in low density polyethylene (LDPE) through melt blending. FS was treated using hexadecyl silane, whereas BA using octyl silane and alkylbenzene sulfonic acid. The related nanocomposites were subjected to pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) and thermogravimetric analysis (TGA) under isothermal and dynamic conditions, respectively. Py-GC-MS results proved that the thermal degradation mechanism did not change in the presence of the nanofillers. The latter suppressed the formation of high molecular weight hydrocarbons and affected the relative amounts of diene/alkene/alkane fragments for each hydrocarbon fraction.Dynamic TGA scans were registered at different heating rates in air. The activation energy (Eα) of thermoxidative degradation was calculated by the Ozawa-Flynn-Wall (OFW) method at various degradation degrees. Eα of the LDPE nanocomposites depended on both specific surface area and surface treatment of the nanofillers used. The former enhanced whereas the latter decreased the activation energy for the LDPE-FS nanocomposites. By contrast, Eα was slightly increased for the surface treated LDPE-BA nanocomposites.