Firstly, we would start with the definition of TiO2 and it’s applications
Titanium dioxide, also known as titanium oxide or titania is the naturally occurring oxide of titanium, chemical formula TiO2.
When used as a pigment, it is called titanium white, Pigment White 6 (PW6), or CI 77891.
Generally, it is sourced from ilmenite, rutile, and anatase. It has a wide range of applications, including paint, some industries, sunscreen, and food coloring.
Titanium dioxide occurs in nature as the minerals rutile and anatase.
Titanium dioxide has eight modifications – in addition to rutile, anatase, akaogiite, and brookite, three metastable phases can be produced synthetically (monoclinic, tetragonal, and orthorombic), and five high-pressure forms (α-PbO2-like, baddeleyite-like, cotunnite-like, orthorhombic OI, and cubic phases) also exist:
When it comes to TiO2 applications, the most important application fields are paints and varnishes as well as paper and plastics, which account for about 80% of the world’s titanium dioxide consumption. Other pigment applications such as printing inks, fibers, rubber, cosmetic products, and food account for another 8%. The rest is used in other applications, for instance the production of technical pure titanium, glass and glass ceramics, electrical ceramics, metal patinas, catalysts, electric conductors, and chemical intermediates.
Secondly, TiO2 Dispersion can be mentioned in many industries and substances as I recommend above but I intend to regarding to plastic industries. We will study better through below analysis
The dispersion of TiO2 was analyzed by scanning electron microscopy. Figure (1a) shows the SEM image at 5000 for the as-received TiO2 powder. This image displays hemispherical particles forming agglomerates. EDX spectrum corroborated the elemental composition of TiO2, besides of titanium and oxygen, these particles contain Al, Si and C (Figure 1b). The Al and the Si are elements usually present in the form of oxides or hydroxides to passivate the surface of TiO2 and the C to enhance the compatibility of the nonpolar polyolefin. The proportion of each detected element in terms of the mass fraction was 9.53, 33.13, 0.62, 0.41 and 56.3 wt% for the C, O, Al, Si, Ti, respectively
Figure 1c is the micrograph of TiO2 incorporation in PE showing that dispersion obtained with the traditional melt-extrusion process (ME) can reduce the size of the agglomerates, presenting clusters of particles from one micron and some isolated particles are also observed. However, the use of USME-VF results in a better dispersion of TiO2 particles in the PE2 polymeric matrix (Figure 1e).
By comparing the signals of the EDX spectra of compound obtained by ME (Figure 1d) and USME-VF (Figure 1f), it is observed that the carbon signal for the polymer matrix is intensified. This effect is more pronounced for the masterbatch prepared by USME-VF method (Figure 1f). This may be due to the fact that TiO2 particle content becomes less detectable since the particles are better distributed in the polymer matrix. This result confirmed that the homogenization in the masterbatch treated with variable frequency ultrasound was promoted, as reported by Bernhardt et al, who performed experiments with ultrasonic energy at low power percentages (3 watts) and different frequencies had found an advantage on the dispersion of dyes and fillers in thermoplastic materials.
SEM Study of the TiO2 Dispersion Developed by USME-VF Method in PE Matrix of Different Rheology
The effect of ultrasonic treatment at a variable frequency range of 15 to 50 kHz on polymeric matrices with different MFIs was analyzed.
This figure shows how the compound morphology changed depending on the polymer MFI. In Figure 2a) it is shown that the compound with the polymeric matrix of the lowest fluidity index (MFI = 2) had marks or gaps close to the interface between the pigment and the polymeric matrix; this may be due to the high viscosity of this polymer. On the other hand, the morphology of the compound with MFI 20 (Figure 2b), presented a more significant aspect of roughness in the polymer matrix than the one with an MFI = 2. This type of morphology has been observed in compounds of PP/TiO2. However, the effect of the ultrasound treatment on the compound with MFI 50 (Figure 2c), showed less evidence of marks or craters in the polymer matrix and in the polymer-pigment interface, this may be because there is a greater relaxation of polymer chains, which are less entanglement due to the lower molecular weight. By comparing the achieved dispersion in the masterbatch concentrates, it is observed that the dispersion of TiO2 in the LLDPE matrix with MFI 2 showed a more excellent uniformity in the distribution of the particles.
In the polymer matrix with MFI 50, the particles tend to bind. It can be considered that the polymer matrix with a higher fluidity index may have more significant movement. Thus, the particles tend to re-agglomerate; this behavior has been observed when obtaining nanocomposites of Nylon 6 and Cu nanoparticles by ultrasound-assisted extrusion; this phenomenon could be occurring for the high fluidity index of LLDPE.
The effect of the ultrasound treatment on the compound with MFI 50 (Figure 2c), showed less evidence of marks or craters in the polymer matrix and in the polymer-pigment interface, this may be because there is a greater relaxation of polymer chains, which are less entanglement due to the lower molecular weight. By comparing the achieved dispersion in the masterbatch concentrates, it is observed that the dispersion of TiO2 in the LLDPE matrix with MFI 2 showed a more excellent uniformity in the distribution of the particles. In the polymer matrix with MFI 50, the particles tend to bind. It can be considered that the polymer matrix with a higher fluidity index may have more significant movement. Thus, the particles tend to re-agglomerate; this behavior has been observed when obtaining nanocomposites of Nylon 6 and Cu nanoparticles by ultrasound-assisted extrusion; this phenomenon could be occurring
This below study is the effect of TiO2 Dispersion on the Film Pigmentation. Figure 3 shows the capacity of the covering power of pigmented films with 7 wt% of TiO2 at 50 microns of thickness
The pigmentation achieved was dependent on the concentration of the masterbatches produced by ultrasonic assisted extrusion process. As control film, the film produced from the concentrate without ultrasound treatment was used.
When the white films were contrasted against a black substrate, the pigmentation of TiO2 was better for samples prepared using the masterbatch concentrates obtained by the USME-VF method.
In addition, it was confirmed that the film pigmentation at the settled concentration of TiO2 at 7 wt% was dependent on the concentration of pigment particles in the masterbatch of MFI 2. As observed in Figure 3, the masterbatch of lower TiO2 concentration the best capacity for covering power of the films.
The capability of pigmentation of the masterbatches was as follow
MB10.PE2. USME-VF > MB20.PE2.USME-VF > MB30.PE2. USME-VF, it could be related to the lower agglomeration or crowding of TiO2 particles at low concentrations.
Investigations carried out using TiO2 as a pigment have indicated that the covering power increases with dispersion of TiO2 in the polymer matrix, due to the different refractive indices of the air and the polymeric compound, which helps give an increase in the contrast range.
Figure 4 shows the SEM images of films prepared using the MB10.PE2 masterbatch resulting of ME and USME-VF, where (a) is MB10.PE2.7% TiO2 control and (b) MB10.PE2.7% TiO2. USW. These images show that the control sample has different areas with the agglomeration of the pigment due to the lumps of the TiO2 particles. On the contrary, in Figure 4b, 4a homogeneous distribution of TiO2 particles can be seen in the polymer matrix; this may be due to the deagglomerating effect by ultrasound energy.
In this study, masterbatch concentrates of TiO2 and LLDPE were prepared by the ultrasoundassisted melt-extrusion method, in variable frequency mode.
It was noticed that the polymeric matrix of lower fluidity (MFI 2) in the masterbatch resulted in a better pigmentation.
Masterbatches of MFI 2 showed a better capacity of pigmentation and covering power in the films when reducing the agglomeration or crowding of TiO2 particles. This result was achieved with the masterbatch at low concentrations of TiO2 (MB10.PE2. USW). The deagglomeration process using variable ultrasound frequency increased the photocatalytic activity of the TiO2 particles of the films exposed to accelerate aging. However, a better mechanical behavior of the elongation at rupture of films was promoted by achieving the deagglomeration of TiO2 particles. The increase in the particle photocatalytic activity was not decisive for degrading the films, and it was found that only after undergoing accelerated aging, the films showed a slight increase in the yellowness index.