The influence of surface-treated nano-TiO2 (rutile) incorporation in water-based acrylic coatings on wood protection

The aim of this research was to synthesize surface-treated nano-titanium dioxide (TiO₂) particles and incorporate them into water-based acrylic systems, which could offer long-term protection for UV-sensible wood substrates. To suppress the photocatalytic activity, the surface of TiO₂ nanoparticles in rutile crystal structure was coated with amorphous silica (SiO₂) layer. The amounts of SiO₂ were 5 and 10 wt%, respectively. Formation of SiO₂ layer on TiO₂ surface was analyzed using scanning and transmission electron microscopy. SiO₂ layer thickness increases as a function of precursor loading. In addition, the influence of SiO₂ loading on rutile UV-protective properties was determined. Transparent UV-protective coatings were developed by incorporating surface-treated nano-TiO₂ into water-based acrylic stain. The particle size distribution was determined using dynamic light-scattering measurements, which indicate that the suspension of surface-treated rutile is stable against agglomeration. Furthermore, the color change and ability of protection against UV light of coatings after nanoparticles incorporation were determined. TiO₂, surface treated with 10 wt% of SiO_2, yielded coatings of higher transparency; however, TiO_2, surface treated with 5 wt% of SiO_2, improved UV protection.     

Functionalization of lyocell fibers with TiO2, SiO2, and GLYMO

In the research self-cleaning coatings based on photocatalytically active nano titanium dioxide (TiO₂) were prepared. When applied directly to cellulose fiber surfaces, TiO₂ coatings form weak bonds with fibers. Therefore 3-glycidooxypropyl-trimethoxysilane was used as a coupling agent. It had been applied on the surface of cellulose fibers before the TiO₂ coating was performed. In this case, the silane is in the interface region, where it can be most effective as an adhesion promoter. Silane coupling agents have unique chemical and physical properties not only to enhance bond strength, but more importantly to prevent de-bonding at the interface during composite aging and use as well. The coupling agent provides a stable bond between two otherwise poorly bonding surfaces. Surface properties of these coatings have been examined, such as surface morphology and surface microstructure. TiO₂ nanoparticles were irreversibly attached to the surface of monodisperse silica (SiO₂) spheres and to the surface of Lyocell fibers coated with an epoxy-containing silane coupling agent. Analysis using scanning electron microscopy showed uniform distribution of nanoparticles in the resulting coatings. Fourier transform infrared spectroscopy revealed changes in the surface microstructure occurring after different modifications. In addition, the influence of photocatalytic activity on the mechanical properties of Lyocell fibers was determined. In addition to that, the results indicated that SiO₂ and the coupling agent provide a protection against high oxidizing power of TiO₂ under exposure to daylight irradiation.     

Self-cleaning and handle properties of TiO2-modified textiles

Self-cleaning surfaces based on photocatalysis are an extremely promising nano-technological field of extensive research and development. Recently comprehensive research work has been performed to evaluate the optical, photocatalytic and antimicrobial properties of TiO₂ nano-particles and composites thereof. The aim of this study was to obtain self-cleaning properties for regenerate cellulose surfaces by nano-modification, using TiO₂ nano-coating and to define the impact of the modification on fabrics end-use properties. Two different modified fabrics with self-cleaning effect were prepared and analysed, i.e. the modification efficiency was determined. In addition, the influence of fibre modification on several textile properties was determined. However, a soft handle, good appearance and some other surface properties accompanied by appropriate mechanical properties represent the basis for a high quality fabric therefore the influence of the modification procedure on textiles handle was studied.     

Homogeneous self-cleaning coatings on cellulose materials derived from TIP/TiO2 P25

The aim of this research was to study TiO₂ nanocoatings formation and to investigate their self-cleaning effects when applied on cellulose materials. Two different approaches for achieving nanocoatings were used. First, coatings were generated in situ through an acid and alkaline catalyzed sol-gel process with or without added water. Another type of coatings was prepared starting from commercial TiO₂ P25 powder. In order to acquire homogeneous coatings from TiO₂ P25 nanoparticles with uniform nanoparticles size distribution, pH of aqueous TiO₂ P25 dispersions was varied. The dispersion preparation conditions were studied by dynamic light scattering (DLS) and zeta potential (ζ-potential) analysis. The resulting TiO₂ nanocoatings were analyzed in terms of their surface morphology using scanning electron microscopy (SEM). Nanocoatings obtained from pure aqueous dispersions of TiO₂ P25 nanoparticles were inhomogeneous with huge agglomerates; however by changing the pH of dispersion and consequently changing the surface charge of TiO₂ P25 nanoparticles as well, more homogeneous nanocoatings with uniform TiO₂ nanoparticles distribution were prepared. Significant differences between solgel derived coatings were observed. Sol-gel process without added water yielded more homogeneous coatings than sol-gel process with addition of water. Completely different surface morphologies were obtained using alkaline or acid catalyst. Acid catalyzed sol-gel process yielded nanocoatings with long, extended, thin structures; contrary, under alkaline conditions particles grow in size with decrease in number. Fourier transform infrared (FTIR) spectroscopy was used to study the coatings’ microstructure. Furthermore the formation of mono-disperse nanoparticles on the fiber surface resulted in enhanced photocatalytic activity. Degradation of colored stain applied on TiO₂-treated samples was investigated by colorimetric measurements. Photocatalytic activity of nanocoatings prepared via acid catalyzed sol-gel process without water addition was comparable to that of nanocoatings derived from aqueous dispersions of commercial TiO₂ P25 nanoparticles.