Performance characteristics of nano titanium dioxide
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Nano-TiO 2 rutile in a product as much, but there are anatase, as well as mixed crystal and amorphous. Nano TiO 2 for automotive topcoats must be surface treated rutile with excellent weatherability.
The nano TiO 2 has the same TiO 2 composition as the ordinary pigment TiO 2 and the same rutile or sharp iron type crystal form. As a basic crystal form, TiO 2 does not change, and naturally has many characteristics of ordinary pigment TiO 2 , such as chemical resistance, thermal stability (rutile type), non-toxicity and the like. However, the ordinary pigment TiO 2 has a particle diameter of 0.2 to 0.4 m (ie, 200 to 400 nm), and it has the same degree of strong reflection for the entire spectrum, so the appearance is white and the hiding power is strong; and the particle size of the nano TiO 2 is large . It is generally 10~50nm, which is 1/10 of the particle size of ordinary pigment TiO 2 . When light passes through the particles, it is diffracted, and it has strong transmission ability to visible light, so it is transparent and loses hiding power. For example, for visible light having a wavelength of 550 nm, the transparency can be more than 90%. However, according to the well-known Rayleigh light scattering theory, such nano-TiO 2 can still reflect blue light in short-wave light such as visible light. Due to the agglomeration of the particles, the nano-TiO 2 present in a powder state can only be translucent, and has a milky white color with a blue tint. Improving the dispersibility and achieving the desired degree of dispersion is one of the biggest research topics of nano-TiO 2 .
Since nano TiO 2 has a different particle size than the ordinary pigment TiO 2 , its particle size is small. With the ultrafine refinement of the particles, there are many nano TiO 2 particles per unit volume or mass, which increases many absorption or scattering points. TiO 2 has greater UV shielding than the conventional pigment TiO 2 . Due to the ultrafine refinement of nano-TiO 2 particles, the specific surface area is greatly increased, and the surface atomic structure and crystal structure are changed. Thus, surface effects, volume effects, quantum size effects, and the like are different from ordinary pigment TiO 2 . Macroscopic quantum tunneling effects, surface interface effects, color effects, flop effects, transparency and optical properties.
As an effect pigment, such as TiO 2 nanoparticles only with other flake pigments and effect pigments of aluminum powder (or) when the pearlescent pigment used to fight, will produce flop. Used in combination with pearlescent granules, it will not weaken but will only enhance the interference color of pearlescent pigments. This flop is opalescent or rainbow, a new sensation that has never been seen before. In the simplest model of nano-TiO 2 -aluminum pigments (such as coating film), when incident light is irradiated on this model, nano-TiO 2 scatters blue light of shorter wavelength in visible light to form blue light. The color of the glancing color is transmitted, and the long-wavelength green light to the red light is reflected by the aluminum powder pigment to form a positive color of golden yellow light. This typical golden yellow color can be changed by adding pearlescent pigments of different colors. The soft color change of the flop effect can change with the curvature of the car body, which is suitable for the current popular round angle and streamlined new models.
The performance of the Japanese Imperial Chemical Company MT series and the German Di Gaosha P-25 nano TiO 2 is shown in Table 1.
Table 1 Japan Imperial Chemical Company MT series and Germany Di Gaosha company
performance
MT-100S
MT-100T
MT-150W
MT-500B
MT-100F
P-25
Exterior
White powder
White powder
White powder
White powder
White powder
White powder
Main treatment agent
Lauric acid
Stearic acid
Stearic acid
Al(OH) 3
Al(OH) 3
Fe(OH) 3
pH value
Neutral to slightly alkaline
neutral
Crystal form 1
R
R
R
R
R
R+A
Moisture /% ≤
2.5
3.0
3.0
1.5
3.0
Burning loss /% ≤
13.0
13.0
7.0
2.5
Surface properties
Hydrophobic
Hydrophobic
Hydrophilic
Hydrophilic
Hydrophilic
Hydrophilic
Average particle size / nm
15
15
15
35
15
twenty one
Specific surface area / (m 2 /g)
50~70
50~70
80~110
30~35
50~70
35~65
90 2
90 2
90 2
1R is rutile and A is anatase.
2 is the specific surface area before surface treatment. [next]
Saatchin Chemical Company of Germany produces nano-sized rutile and anatase TiO 2 , of which the anatase series is L5 and the rutile series is RM. The RM nano TiO 2 technical data is listed in Table 2.
Table 2 Sabinbin RM nano TiO 2 technical data
index
RM120
RM200
RM220
RM300
RM400
TiO 2 content /%
80
88
>88
88
>8
Rutile content /%
99
>99
>99
>99
>99
Specific surface area / (m2 / g)
110
50
45
60
110
pH value
6.5
6.5
6.5
6.5
6.5
Grain size / nm
13
15
20
15
10
Density / (g / cm 3 )
4
4
4
4
4
Weather resistance
good
general
excellent
excellent
excellent
Dispersibility
very good
very good
very good
very good
very good
The properties of nano-TiO 2 produced by Japan Ishihara Industry Co., Ltd. are shown in Table 3.
Table 3 Properties of nano-TiO 2 produced by Japan Ishihara Industry Co., Ltd.
Crystal form
TiO 2 content /%
Surface treatment agent
Particle size / nm
Specific surface area / (m 2 /g)
Surface properties
TTO-55A
Rutile
95~97
Al
30~50
35～45
Hydrophilic
TTO-55B
Rutile
90～97
Al
30~50
35～45
Hydrophilic
TTO-55C
Rutile
86～92
Al, stearic acid
30~50
25~35
Hydrophobic
TTO-55D
Rutile
76～81
Al, Zr
30~50
65~80
Hydrophilic
TTO-55S
Rutile
94 to 96
Al, organosiloxane
30~50
30~40
Hydrophobic
TTO-55N
Rutile
96～99
no
30~50
35～40
Hydrophilic
TTO-55A
Rutile
76～82
Al
10~30
75～85
Hydrophilic
TTO-55B
Rutile
81～87
Al, lauric acid
10~30
50-65
Hydrophobic
TTO-55C
Rutile
79～85
Al, stearic acid
10~30
50~60
Hydrophobic
TTO-55D
Rutile
65~75
Al, Zr, lauric acid
10~30
70～80
Hydrophobic
TTO-F-1
Rutile
72～78
Al, Zr 1
30~50
75～90
Hydrophilic
TTO-F-2
Rutile
82～90
Al 1
30~50
34~42
Hydrophilic
1 It has skin color due to iron and is mainly used in the manufacture of cosmetics.
In recent years, Imperial Chemical Co., Ltd. has introduced color nano-TiO 2 coated with Al, Si, Fe (skin) or Ni, Co, Ce, Cu, Cr, Mn, V, W and other oxides on the surface of the particles (other colors) ) made of.