Modified titanate nanotubes for application as nanofillers in polymers

Titanate nanotubes (TiNTs) are extensively studied due to some distinct advantages, including the ease with which they can be prepared in high purity and high yield, a low cost, a high specific surface area, a high density of surface OH-groups, ion-exchange and semiconducting properties [1, 2]. Due to the high density of surface OH-groups, TiNTs are a promising material for surface modifications, particularly with functionalized alkoxysilanes, (RO)3Si−R’X, where R’X denotes an alkyl chain terminating with a functional group X. Depending on the nature of the group X, the physical and chemical properties of the TiNT surface can be varied so a range and the potential field of application. TiNTs are expected to be promising nano- Fig. 1. (a) Titanate nanotubes modified with (3- aminopropyl)trimethoxy silane, (b) APTMS modified nanotubes inbuilt in polymer, (c) smaller and (d) larger nanotube aggregates of nanofiller in polymer filler for polymer composite materials, since their modulus is comparable to that of carbon nanotubes, while the chemistry of their surface modification is the same as for conventional inorganic fillers. In this work [3], chemically modified TiNTs were studied. The aim was to prepare TiNTs surface-modified with (3- aminopropyl)trimethoxy silane (APTMS) and study of their usage for polymer reinforcement. TiNTs were surface-modified with APTMS by novel method suitable for syntheses of large amounts of materials with low costs. TEM was used for the investigation of the prepared nanotubes, while the polymer nanocomposite was examined by SEM working in STEM mode. The thermal stability of nanofiller, important to preserve their functional properties, was studied by in situ high temperature Raman spectroscopy before inbuilt in polymer. The most temperature stable sample, was used for preparation of epoxy-based nanocomposites (Fig. 1a). All the APTMS modified TiNT were bond well with the epoxy matrix (Fig. 1b) because amine groups on the TiNTs surface can react with epoxy group to form covalent bonds between the matrix and the nanofiller. The nanofiller formed smaller and larger aggregates in polymer (Figs 1c and d), where the amount of aggregates increase with addition of nanofillers. Small addition of nanotubes (0.19– 1.52 wt%) significantly increased the glass transition temperature and the modulus in rubbery state of the epoxy based polymer. A smaller amount of added nanofiller provide larger increase in these parameters and therefore better dynamic mechanical properties. Such behaviour was explained by the smaller amount of large aggregates then in the case of more nanofiller added. In this work APTMS modified TiNTs were proved as promising nanofiller in epoxy based nanocomposits.