Silicone Fluids and Silicone Emulsions from WACKER - Wacker Chemie AG


Silicone Fluids and Silicone Emulsions from WACKER

Silicones are particularly stable and exceptionally resistant to such influences as heat and electromagnetic radiation. Above all, silicone fluids from WACKER are ideal for use in all kinds of industries – cosmetics, pharma and textiles, to name but a few.

Definition and Properties of Silicones

Silicones consist of an inorganic backbone made of alternate silicon and oxygen atoms. Chemists refer to them as polydiorganosiloxanes. The two other valencies of the silicon atoms are occupied with organic groups (mainly methyls). These are responsible for silicones' semi-organic nature.

The bond energy of a silicon-silicon bond is much greater than that of a carbon-carbon bond. This make silicones much more stable and more resistant to diverse influences.

A key advantage of silicone fluids is their excellent thermal and thermooxidative resistance. More precisely, they are resistant to temperatures ranging from -60 to +300°C.

Silicone fluids are also much more stable than organic polymers toward electromagnetic and particle radiation (UV, alpha, beta and gamma radiation) .. Silicone fluids additionally possess

  • Extremely low volatility
  • Excellent shear stability
  • Low surface tension, and
  • Optimum water repellency.

Silicone fluids have no known harmful effects and are transparent liquids that have no taste or odor. Their viscosities lie between 0.65 and 1,000,000 mm2/s, depending on the type. Since there are only very weak intermolecular forces between the individual methylsilicone chains, they are liquid over wide ranges of their molecular weight.

Viscosity [mPa s] Molecular weight [D] Mean chain length
0.65 162 2
10 1200 16
100 5200 70
1000 15000 200
10000 37000 500
100000 74000 1000

Thanks to these properties, silicone fluids make ideal

  • Hydraulic and transformer fluids,
  • Damping fluids,
  • Diffusion pump fluids,
  • Heat-resistant lubricants,
  • Dielectrics,
  • Defoamers and
  • Release agents for high-performance digital-printing machines.

They are also used for water-repellent treatment of glass and mineral wool and for various applications in cosmetics, pharmaceuticals and textiles.

Silicone fluids are the starting materials for further silicone products which are created by chemical functionalization. The siloxane backbone is most often modified in two ways:

  1. Instead of methyl groups, longer alkyl chains are attached
  2. . Functionalization is performed with organic polymers . For example, polyethylene oxide, polypropylene oxide or alkylamino groups can be used for this.

This affords a way of transforming hydrophobic silicone fluids into more or less hydrophilic molecules

. Reactive silicone fluids are siloxanes terminated with reactive groups. They include, e.g., OH polymers (hydrolyzates) or silicone fluids with amino or epoxy groups.

Silicone fluids are often used in the form of aqueous emulsions. As these can be readily diluted with water, small amounts of the substance can be uniformly distributed on substrates.

There are basically two types:

  1. Macroemulsions with particle sizes from 100 nm to several µm. These are usually opaque, i.e. milky.
  2. Microemulsions with particle sizes less than 100 nm. These are usually clear or opalescent.

To provide a stable silicone emulsion, the surfaces of the fluid droplets are covered with surfactants (emulsifiers). The lipophilic – oil-loving – ends of the emulsifier are oriented toward the oil droplet. The hydrophilic – water-loving – centers provide the solubility in water.

Silicone emulsions are typically used in the textile, cosmetic and household care industries. As components of shampoos, silicone emulsions lend hair a silky softness, making it easy to comb after washing. Silicone emulsions are also used as water-repellent agents for protecting textiles or building and insulation materials against water and damp.

Silicone pastes can be used in various applications by virtue of their basic properties:

  • They do not harden and their properties are largely unaffected by changes in temperature.
  • They are water-resistant, water-repellent and oxidation-resistant. They are thus extremely durable and form protective layers against the elements and on a wide range of surfaces.
  • They are odorless, of a low order of toxicity, radiation resistant up to approx. 106 rad, inert with respect to a great many chemicals, and resistant to microorganisms.
  • They have ready adhesion to numerous surfaces, good lubricating properties in plastic/plastic or plastic/metal pairings, and good lubricity.
  • They have good release action with respect to numerous elastomers and plastics.
  • They guarantee good electrical insulation. They also have a high breakdown strength, high dielectric constant and low loss factor.
  • They are very stable in storage. Functionality of specific properties lasts for up to 12 months while general properties will last for several years.

Silicone pastes are used, for example, as lubricants and installation aids, both for technical purposes and in food-contact applications, and as sealing aids for sealing parts and connections that can be disassembled, and as release agents for high-temperature use.

Silicone waxes are polydimethylsiloxanes that are modified by long-chain alkyl groups. To an extent depending on the chain length and number of alkyl groups, modification yields products of different melting point. These behave like typical hydrocarbon waxes.

Silicone waxes combine the properties of organic waxes – such as water repellency or providing structure – with the typical properties of silicones, such as wetting power and good sensory properties.

They are thus ideally suited to all applications in which lubrication is required and the transition from solid to liquid is critical. Silicone waxes are used as oil and wax components in skin and face creams, or in decorative cosmetic articles for improving the skin feel. In addition, silicone waxes optimize the distribution of pigments and sunscreen additives and increase the spread of oils and active compositions. In the textile sector, for example, leather is treated with silicone waxes. These confer very good long-term protectionand have a water-repellent effect.

Silicone Antifoam Compounds These are oily, viscous, opaque or slightly cloudy liquids. They are mostly used in systems containing little or no water. The compounds can be used neat or mixed with suitable formulation components such as surfactants.

Self-Dispersing Silicone Antifoam Agents These are a combination of antifoam agent compounds with organic active agents and auxiliaries. They disperse spontaneously on contact with foaming formulations and show good compatibility and spreading properties.

Silicone Antifoam Emulsions These are o/w emulsions of antifoam agent compounds with an active ingredient content of 5 to 50%. They are mainly used for water-borne formulations and applications.

Silicone Antifoam Powders These are ideal for use in powder products, such as powder-form detergents.

Silicone Fluids These are characterized by good antifoam properties in water-free, non-polar systems. They are suitable for applications in which compatibility with other substances is not required.

Silicone fluids are characterized by a very high thermal and thermooxidative resistance and have excellent resistance to temperatures from -60 to +300°C. Silicone fluids are also much for stable than organic polymers toward electromagnetic and particle radiation (UV, alpha, beta and gamma radiation). Moreover, silicone fluids are characterized by very low volatility, excellent shearing resistance, low surface tension and very good water repellency.

Silicone fluids are transparent, tasteless and odorless liquids with no known harmful effects. Their viscosities lie between 0.65 and 1,000,000 mm2/s depending on the type. Since there are only very weak intermolecular forces between the individual methylsilicone chains, they have a liquid consistency over wide ranges of their molecular weight. An overview of this is provided by the following table:

Viscosity [mPa s] Molecular weight [D] Mean chain length
0.65 162 2
10 1200 16
100 5200 70
1000 15000 200
10000 37000 500
100000 74000 1000

Silicone fluids are ideal for use as hydraulic or transformer oils, damping liquids, diffusion pump fluids, thermally resistant lubricants, dielectrics, defoamers and release agents for high-performance digital printing machines. They can also be used for hydrophobic treatment of glass and mineral wool. Other important applications are to be found in cosmetics, pharmaceuticals and the textile industry.

Due to chemical functionalization, a large number of other silicone products are derived from silicone fluids. Essentially, the siloxane backbone is modified in two ways: Either longer alkyl chains are attached instead of the methyl groups, or functionalization with organic polymers is performed. For example, polyethylene oxide, polypropylene oxide or alkylamino groups can be used for this. This selectively modifies the silicone fluids, allowing hydrophobic silicone fluids to be transformed into more or less hydrophilic molecules. If siloxanes have reactive groups as terminal chain members, they are known as reactive silicone fluids. They include e.g., OH polymers (hydrolyzates) or silicone fluids with amino or epoxy groups.

Silicone fluids are often used in the form of aqueous emulsions. In this form, they can be further diluted with water, allowing a uniform distribution of small amounts of the substance on the substrates. In principle, a distinction is made between (usually opaque, i.e. milky) macroemulsions with particle sizes from 100 nm to several µm and (usually clear or opalescent) microemulsions, with particle sizes below 100 nm. To provide a stable silicone emulsion, the surfaces of the fluid droplets are covered with surfactants (emulsifiers). The lipophilic (oil-loving) ends of the emulsifier are oriented towards the oil droplet, while its hydrophilic (water-loving) centers govern the solubility in water.

Silicone emulsions are used in many application areas, such as the textile, cosmetic and household care industries. As formulation ingredients in shampoos, silicone emulsions lend hair a silky softness, making it easy to comb after washing. As hydrophobizing additives, silicone emulsions protect textiles or building and insulation materials against water and damp.

Silicone pastes can be used as valuable functional aids in very different fields of application, thanks to their basic properties:

  • Non-curing, pasty consistency largely unaffected by temperature, permitting use over a broad temperature range
  • Water resistant, water repellent, oxidation resistant, hence offering long-term resistance to atmospheric influences, forms a protective layer
  • Odorless, of a low order of toxicity, radiation resistant up to approx. 106 rad, inert with respect to a great many chemicals, resistant to microorganisms
  • Ready adhesion to numerous surfaces, good lubricating properties in plastic/plastic or plastic/metal pairings, good lubricity
  • Good release properties with respect to numerous elastomers and plastics
  • Good electrical insulation, high dielectric strength and permittivity, low loss factor
  • Excellent shelf life, guaranteed functionality of specific properties for up to 12 months and of general properties for several years

Silicone pastes are used, for example, as lubricants and installation aids, both for technical purposes and in food-contact applications, and as sealing aids for sealing parts and connections that can be disassembled, and as release agents for high-temperature use.

Silicone waxes are polydimethylsiloxanes that are modified by long-chain alkyl groups. Depending on the chain length and number of alkyl groups, the products may have different melting points and behave like typical hydrocarbon waxes. Silicone waxes combine the properties of organic waxes – such as water repellency or providing structure – with the typical properties of silicones, such as wetting power and good sensory properties. Silicone waxes are particularly suitable for all applications in which lubrication is required and the transition from solid to liquid is critical. Silicone waxes can be used as oil and wax components in skin and face creams, or in decorative cosmetic articles for improving the skin feel. In addition, silicone waxes improve the distribution of pigments and sunscreen additives and greatly increase the spread of oils and active compositions. In the textile field, they provide leather with very good long-term protection and provide water repellency.

Silicone Antifoam Compounds

  • Oily, viscous, opaque or slightly cloudy liquids
  • They are mostly used in systems containing little or no water
  • Compounds can be used neat or mixed with suitable formulation components such as surfactants.

Self-Dispersing Silicone Antifoam Agents

  • Combination of antifoam agent compounds with organic active agents and auxiliaries
  • Disperse spontaneously in contact with foaming formulations
  • Show particularly good distribution and compatibility

Silicone Antifoam Emulsions

  • O/w emulsions of antifoam agent compounds with an active ingredient content of 5 to 50%
  • This product form is mainly used for water-based formulations and applications
  • Silicone Antifoam Powders
  • The powder-form antifoam agents are specifically intended for powder products, e.g. powder detergents.

Silicone Fluids

  • These are characterized by good antifoam properties in water-free, non-polar systems
  • Suitable for applications in which compatibility with other substances is not required

Silicones, known to chemists as polydiorganosiloxanes, consist of an inorganic backbone made of alternate silicon and oxygen atoms. The other two valencies of the silicon atoms are occupied with organic groups (preferably methyls), which are responsible for silicones’ semi-organic nature. The Si-O bond energy is significantly greater than that of a C-C bond. This has far-reaching effects on the stability and resistance of silicones to a variety of influences.

Find out more about silicone and its properties:

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