Registration Dossier

Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

4.1 Appearance / physical state / colour

Study

Form of silica, surface treated, BET range

Guideline (or method), GLP (yes/no), reliability

Results

Key_appearance_xxx_ RL1

Precipitated, no, low

IR-spectroscopy, yes, 1

Solid: particulate / powder, white, odourless, inorganic

 

4.2 Melting point / freezing point

Study

Form of silica, surface treated, BET range

Guideline (or method), GLP (yes/no), reliability

Results

Melting point, literature, RL4

unspecified

Literature data, no, 4

1710 – 1736 °C

3110 °F

key_melting point_xxx_surface-treated_RL1

Pyrogenic, yes, medium

EU method A.1, yes, 1

> 800 K / 526.9°C

 

4.3 Boiling point

Study

Form of silica, surface treated, BET range

Guideline (or method), GLP (yes/no), reliability

Results

key_boiling point_xxx_surface-treated_RL1

Pyrogenic, yes, medium

EU method A.2, yes, 1

> 800 K / 526.9°C

 

4.4 Density

Study

Form of silica, surface treated, BET range

Guideline (or method), GLP (yes/no), reliability

Results

key_Skeleton density, xxx, low end

Gel, no, low

OECD 109, yes, 1

Skeleton density

1.81 g/l

key_Skeleton density, xxx, high end

Pyrogenic, no, medium

OECD 109, yes, 1

Skeleton density

2.38 g/l

 

4.5 Particle size distribution

Low end D50 value is 0.33 µm for Aerosil OX 50, a pyrogenic form of SAS

High end D50 value is 680 µm for HDK V15A, also a pyrogenic form of SAS.

Similar to the BET, density also these PSD values (which belong here to agglomerates) represent an overall range of the various SAS products.

Study

Form of silica, surface treated, BET range

Guideline (or method), GLP (yes/no), reliability

Results

key_PSD_xxx_RL1 low end

Pyrogenic, no, low

ISO 13320 (laser diffraction), yes, 1

d50 = 0.33 µm

key_PSD_xxx_RL1 high end

Pyrogenic, no, medium

ISO 13320 (laser diffraction), yes, 1

d50 = 680 µm

 

4.8 Water solubility

Water solubility of all non-surface-treated SAS products (silica gel, colloidal, precipitated and pyrogenic SAS) is in the range of 100 mg/L or higher.

Applying a modified method to accomplish sufficient material wetting, all hydrophobic SAS products analysed (surface treated pyrogenic SAS only) exhibit a solubility between 100 and 160 mg/L in 10 % ethanol/water. It is expected, that other SAS products not tested so far will fit into that range. Thus, we conclude that the solubility of hydrophobic SAS (surface-treated SAS) products does not differ from the results of hydrophilic SAS (non-surface-treated SAS).  

 

Study

Form of silica, surface treated, BET range

Guideline (or method), GLP (yes/no), reliability

Results

key_water solubility OECD 105_xxx_RL1

Precipitated, no, high

EU method A.6 / OECD 105, yes, 1

135.4 ± 4.4 mg/L

key_water solubility OECD 105_xxx_RL1

Gel, no, high

EU method A.6 / OECD 105, yes, 1

142.9 ± 3.4 mg/L

key_water solubility OECD 105_xxx_RL1

Pyrogenic, no, high

EU method A.6 / OECD 105, yes, 1

222.8 ± 5.7 mg/L

key_water solubility OECD 105_xxx_RL1

Precipitated, no, low

EU method A.6 / OECD 105, yes, 1

108.3 ± 6.0 mg/L

key_water solubility OECD 105_xxx_RL1

Gel, no, low

EU method A.6 / OECD 105, yes, 1

87.2 ± 5.2 mg/L

key_water Solubility OECD 105_xxx_RL1

Gel, no, medium

EU method A.6 / OECD 105, yes, 1

106.0 ± 3.6 mg/L

key_water solubility OECD 105_xxx_RL1

Precipitated, no, low

EU method A.6 / OECD 105, yes, 1

108.1 ± 5.6 mg/L

key_water solubility OECD 105_xxx_RL1

Pyrogenic, no, high

EU method A.6 / OECD 105, yes, 1

232.6 ± 6.8 mg/L

key_water solubility OECD 105_xxx_RL1

Gel, no, low

EU method A.6 / OECD 105, yes, 1

98.1 ± 2.7 mg/L

key_water solubility OECD 105, Aerosil xxx_RL1

Pyrogenic, no, low

EU method A.6 / OECD 105, yes, 1

117.9 ± 6.7 mg/L

key_water solubility OECD 105_xxx_RL1

Pyrogenic, no, medium

EU method A.6 / OECD 105, yes, 1

201.6 ± 5.3 mg/L

key_transformation/dissolution OECD 29_High Surface Precipitated SiO2_RL1

Precipitated, yes, high

OECD Series on Testing and Assessment No. 29, yes, 1

990.5 µg/L (c. 99%) with 1 mg/L nominal load

key_water solubility OECD 105_xxx_RL1

Precipitated, no, medium

EU method A.6 / OECD 105, yes, 1

111.9 ± 0.9 mg/L

key_transformation/dissolution OECD 29_xxx_RL1

Colloidal, no

OECD Series on Testing and Assessment No. 29, yes, 1

990.5 µg/L (c. 99%) with 1 mg/L nominal load

 

4.9 Solubility in organic solvents / fat solubility

Study

Form of silica, surface treated, BET range

Guideline (or method), GLP (yes/no), reliability

Results

key_Solubility in Ethanol OECD 105_xxx_RL2

Precipitated, no, low

OECD 105, yes, 1

< 0.49 mg/L

 

4.12 Auto flammability

Study

Form of silica, surface treated, BET range

Guideline (or method), GLP (yes/no), reliability

Results

supporting_Dust-Autoignition_xxx_surface treated_RL1

Pyrogenic, no, medium

VDI 2263 part 1, no, 1

No self-ignition

supporting_self-ignition of dust accumulation_xxx_surface treated_RL2

Pyrogenic, yes, high

ASTM E1491 / ASTM E2019 / ASTM E2021, no, 2

725 °C in the MAIT test; no ignition at 450 °C (max. temperature) in the MIT test

supporting_self-ignition of dust accumulation_xxx_surface treated_RL2

Pyrogenic, yes, medium

ASTM E1491 / ASTM E2019 / ASTM E2021, no, 2

750 °C in the MAIT test; no ignition at 450 °C (max. temperature) in the MIT test

 

4.13 Flammability

Study

Form of silica, surface treated, BET range

Guideline (or method), GLP (yes/no), reliability

Results

key_flammability_xxx _surface treated_RL1

Pyrogenic, yes, medium

EU method A.10, yes, 1

not highly flammable as it failed to ignite in the preliminary screening test

key_flammability_xxx_RL2

Pyrogenic, no, high

Burning rate test, yes, 2

substance does not ignite, therefore not flammable

 

4.14 Explosiveness

Study

Form of silica, surface treated, BET range

Guideline (or method), GLP (yes/no), reliability

Results

key_Dust-Explosiveness_xxx_RL2

Pyrogenic, no, medium

VDI 2263 part 1, no, 2

not explosive

 

 

 

4.21 Dissociation constant

Study

Form of silica, surface treated, BET range

Guideline (or method), GLP (yes/no), reliability

Results

key_dissociation, solubility_SAS_RL2

Synthetic amorphous silica (SAS)

Separation by centrifugation / molybdic-acid method, no, 2

pKa 6 - 6.65 at 40°C

 

4.28.4 Nanomaterial aspect ratio / shape

Study

Form of silica, surface treated, BET range

Guideline (or method), GLP (yes/no), reliability

Results

key_aspect ratio_shape_xxx_RL1

Precipitated, no, high

size of the intergrown primary structures: TGZ-method / SEM & TEM, yes, 1

Number of evaluated fine structures (N): 2014

Arithmetical average (DN) nm: 3.1

Standard deviation (S) nm: 0.69

Averaged over the surface (DA) nm: 3.6

Calculated specific electron microscopic surface area (EMS) m²/g: 799

key_aspect ratio_shape_xxx_RL1

Precipitated, no, medium

size of the intergrown primary structures: TGZ-method / SEM & TEM, yes, 1

Number of evaluated fine structures (N): 2003

Arithmetical average (DN) nm: 10.0

Standard deviation (S) nm: 2.58

Averaged over the surface (DA) nm: 11.4

Calculated specific electron microscopic surface area (EMS) m²/g: 239

key_aspect ratio_shape_xxx_RL1

Pyrogenic, no, low

size of the intergrown primary structures: TGZ-method / SEM & TEM, yes, 1

Number of evaluated fine structures (N): 2147

Arithmetical average (DN) nm: 41.4

Standard deviation (S) nm: 18.3

Averaged over the surface (DA) nm: 55.9

Calculated specific electron microscopic surface area (EMS) m²/g: 49

key_aspect ratio_shape_xxx_RL1

Pyrogenic, no, medium

size of the intergrown primary structures: TGZ-method / SEM & TEM, yes, 1

Number of evaluated fine structures (N): 2002

Arithmetical average (DN) nm: 7.8

Standard deviation (S) nm: 1.79

Averaged over the surface (DA) nm: 8.7

Calculated specific electron microscopic surface area (EMS) m²/g: 315

 

4.28.5 Nanomaterial specific surface area

 

The BET range covered by the SAS dossier is 4 to 1.000 m²/g overall for the four forms as the

commercial relevant/commercialized grades –, silica gel, precipitated, colloidal and pyrogenic

SAS while the individual forms only cover a specific range herein. The individual BET ranges for:

 

- Silica Gel is 10 to 1000 m²/g

- Precipitated SAS is 4 to 800 m²/g

- Colloidal SAS is 20 to 500 m²/g

- Pyrogenic SAS is 50 to 400 m²/g

 

Study

Form of silica, surface treated, BET range

Guideline (or method), GLP (yes/no), reliability

Results

BET_xxx_RL2

Gel, no, high

BET, no, 2

915.186 m²/g

BET_xxx_RL2

Precipitated, no, low

BET, no, 2

36.676 m²/g

 

4.28.6 Nanomaterial Zeta potential

Study

Form of silica, surface treated, BET range

Guideline (or method), GLP (yes/no), reliability

Results

key_zeta potential _xxx_RL1

Gel, no, low

Colloidal Vibration Current of a pre-treated dispersion, yes, 1

Mean Value [mV]:

-37.5

Std. Deviation [mV]: 0.094

key_zeta potential _xxx_RL1

Gel, no, medium

Colloidal Vibration Current of a pre-treated dispersion, yes, 1

Mean Value [mV]:

-32.03

Std. Deviation [mV]: 0.694

key_zeta potential _xxx_RL1

Precipitated, no, low

Colloidal Vibration Current of a pre-treated dispersion, yes, 1

Mean Value [mV]:

-40.23

Std. Deviation [mV]: 0.236

key_zeta potential _xxx_RL1

Precipitated, no, high

Colloidal Vibration Current of a pre-treated dispersion, yes, 1

Mean Value [mV]:

-39.6

Std. Deviation [mV]: 0.330

key_zeta potential_xxx_RL1

Pyrogenic, no, low

SOP STO-055, yes, 1

Mean Value [mV]:

-38

Std. Deviation [mV]: 0.14

key_zeta potential _xxx_RL1

Precipitated, no, low

Colloidal Vibration Current of a pre-treated dispersion, yes, 1

Mean Value [mV]:

-30.43

Std. Deviation [mV]: 0.170

 

4.28.8 Nanomaterial dustiness

Synthetic amorphous silica (SAS) is a class of solid, particulate materials, which are composed of nano sized constituent particles. For most SAS materials, the constituent particles are bound in aggregates, which form even larger agglomerates over several length scales. The granulometry refers also to the size of aggregates and agglomerates. The sizes are affected by the environmental conditions, the mixing state and the dispersing forces experienced during processing.

Conventional and standardised dustiness methods do not cover these factors sufficiently, for a complete characterisation of the granulometric state a substitute method represent a multitude of measurement techniques are required to provide more reproducible SAS dustiness equivalent values for the health relevant fractions.

Additional information