Abstract:
In this research, the use of layered double hydroxides (LDHs) as ultraviolet (UV) light-protecting additives for
PP is explored. Different LDHs, such as ZnTi, ZnSn, ZnGa, ZnCr and CdCr LDHs, were prepared and their UV
absorptions were characterized. The ZnTi LDHs showed higher UV absorption than the other four metallic
combinations and were further organically modified with dodecylbenzene sodium sulfonate (SDBS) and
lauric acid (LA). Nanocomposites of polypropylene (PP) with four different types of LDHs, ZnTi, ZnSn,
ZnTi-SDBS and ZnTi-LA, were prepared at concentrations of 5%. The crystallinities and layered structures
of all the metallic combinations of LDHs were characterized by wide angle X-ray spectroscopy (WAXS)
and ultraviolet visible (UV-vis) absorption spectroscopy, and their crystal morphologies were studied by
scanning electron microscopy (SEM). The decomposition and thermal properties of the nanocomposites
and pure PP were analyzed by thermogravimetric analysis (TGA) and transmission electron microscopy
(TEM) and by their photo-oxidation behavior. The addition of these organically modified and unmodified
LDHs showed significant changes in the thermal decomposition of PP. The thermal stability of PP was
increased to around 70 C by the addition of SDBS-modified ZnTi LDHs (5% by weight), and an increase
in induction time of about 300% was determined.
