Silicate(2-), hexafluoro-, disodium, reaction products with lithium magnesium sodium silicate

Particle size distribution (Granulometry)

Description of key information

LAPONITE Type 1 products are placed on the market in the form of a finely divided granular powder.

 

The powder granules are composed of aggregates of nano-sized particles. The powder granules are micro-sized particles. Hence Laponite Type 1 is supplied to downstream users as a powder product with micro-sized particles.

During use in most application fields the user will add LAPONITE Type 1 powder product into water with mixing. The aggregates will wet out, hydrate and disperse into individual primary particles, giving a translucent, colourless and stable dispersion of nanoparticles, also called a colloidal dispersion.

In some application fields, LAPONITE Type 1 powder is wetted out into non-aqueous fluids, such as mineral or silicone oils or polyols. In such cases LAPONITE Type 1 does not disperse into individual primary particles and a colloidal dispersion is not formed.

 

A by-product is formed during the synthesis process to manufacture LAPONITE Type 1. The by-product, a mineral which is also present in nature, is a soft crystalline material, neighborite, NaMgF3. The neighborite in LAPONITE Type 1 is in the form of an insoluble granular powder in the micron size range at a level of <5% by mass. Unlike the synthetic silicate component of LAPONITE Type 1, neighborite does not break down into smaller particles when dispersed into water, but forms a wetted out micron-sized particle. Dispersions of LAPONITE Type 1 in water are hazy in appearance as a result of the presence of neighborite. Neighborite does not contain nanomaterials.

 

Measurements by analytical techniques such as AFM, TEM, SAXS and comparisons made with similar materials, naturally occurring layered silicates, hectorite and montmorillonite indicate that LAPONITE Type 1 primary particles have a layer structure, and are disc-shaped. According to the Commission Recommendation of 18 October, 2011, on the definition of nanomaterial (2011/696/EU), 100% of the synthetic silicate component of LAPONITE Type 1 is classified as a nanomaterial.

Some grades of LAPONITE Type 1 contain additives; these are either water soluble salts or polymer materials, which are not nanomaterials.

 

Typical particle size measurements of LAPONITE Type 1 materials in these two different physical states, powder as supplied and dispersed colloid, are shown below:

 

Powder as supplied (D50)

D10 = 2.0µm, D50 = 29.7µm, D90 = 85.0µm, D99 = 105.2µm (1)

(1) Sympatec particle size analyser, Helos H0399, incorporating a Retsch Vibri feeder, Rodos and venturi (laser deflection on powder dispersed in air)

 

Dispersed colloid (Z50)

Z50 = 37.0nm (2)

Typically, the disc shaped Laponite Type 1 primary particle is 0.9-1.0nm in thickness (x Dimension) and 4.0-73.0nm in diameter (y and z Dimensions)

(2) Malvern Zetasizer Nano ZS (Dynamic Light Scattering – DLS – on 1% solids dispersion in deionized water)

 

The dispersed particles have a negative charge on the surface and a positive charge on the edge of the disc. When LAPONITE Type 1 is dispersed in water and used in a formulation, such as a paint, drilling fluid or cosmetic product, the oppositely charged edges and faces form electrostatic associations with each other. The charged sections of the LAPONITE Type 1 discs can also form associations with oppositely charged sections of other particles, such as dispersion resins and pigments and also molecules, such as polymers that are present in the formulation. These associations form a single continuous network that extends throughout the whole of the container that is holding the formulation. It is this network of particle-particle and particle-polymer associations which develops the very high levels of viscous structure that is typical of formulations containing LAPONITE Type 1. These viscous structures are micro-sized. The viscous structure can be reduced under shear forces, such as mixing or pumping and will build up again when shear forces are removed.

 

Typical use levels of LAPONITE Type 1 in a formulation can range from 0.1% up to 5% or higher.

Additional information

This determination was carried out using a Sympatec laser diffraction PSD analyser incorporating a Retsch Vibri feeder, Rodos and venturi for dry power analysis.