Lightweight ceramic nanotubes reinforced polymer composite coatings and electrospun microfibres

Abstract

The reinforcement of soft ductile polymers with hard brittle ceramic materials in order to improve mechanical and tribological properties of such composites has been explored since the dawn of the polymer technology. The recent advances in synthesis of nanosized materials have further extended the range of suitable fillers for polymer matrices, with particular attention focused on lightweight ceramic elongated nanomaterials. This research is concerned with a prospective approach to enhance mechanical and tribological properties of novel polymer composites by incorporation of titanate nanotubes and other metal oxide elongated nanostructured materials which could also enable the introduction of several responsive functionalities to new nanocomposites such as controlled release of encapsulated chemicals after a specific stimulus.

In this work, methods for isolation of single nanotubes from their agglomerates are developed by long-term mechanical stirring in a choice of suitable solvents with/without ultrasound treatment as well as nanotube surface modification (e.g. addition of CTAB). Colloidal suspensions of titanate nanotubes are affected disparately under ultrasound depending on the surrounding media, resulting in a different extent of shortening. Besides, it has been demonstrated that encapsulation of ibuprofen can be accomplished via polypyrrole sealing followed by its controlled release under short duration of ultrasonication.

A comprehensive study of mechanical and tribological properties of polyethylene oxide/chitosan (PEO/CS) composites reinforced with different content of various elongated nanofillers incorporated from stable aqueous suspensions is shown in addition to a systematic investigation of such properties as a function of length in titanate nanotubes controlled by ultrasound. It is demonstrated that increasing of the concentration of titanate nanotubes (TiNT) leads to improvement in hardness, Young’s modulus, friction coefficient and residual depth. Short duration of sonication of colloidal suspensions of TiNT in the presence of polymer prior to drop-casting has resulted in enhanced mechanical and tribological properties probably due to better dispersion. However, further ultrasound treatment of the mixture leads to deterioration of properties in composites along with nanotube shortening, as observed by TEM.

Subsequent investigations into the manufacture of titanate nanotubes embedded in poly ethylene oxide microfibres via electrospinning technique reveal that although our initial attempts to incorporate TiNT into electrospun microfibers have resulted in poor dispersion, long mechanical stirring of nanotubes in aqueous suspensions of the cationic surfactant CTAB has been essential for the manufacture of electrospun microfibres with high loads of single isolated TiNT (up to 13 wt %) aligned parallel to the electrospinning direction, as confirmed by TEM data.

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