Chemistry
Siloxanes
Siloxanes are fundamental members of the broad family of silicone materials.
What are cyclic siloxanes?
Cyclic siloxanes (cyclosiloxanes) are basic members of the broad family of silicone materials and are used as building blocks for the production of a diverse array of silicone polymers. A common denominator for cyclosiloxanes is that they contain repeating units of silicone (Si) and oxygen (O) atoms in a closed loop, giving it a “cyclic” structure.
This also gives them their unique properties as hybrid inorganic-organic substances. D4, D5, D6 contain 4, 5 and 6 repeating units respectively. They are the three main cyclosiloxanes in commercial production and several decades of research have proven that they are safe for human health and the environment.
Properties of D4, D5 and D6
Properties | D4 | D5 | D6 |
Melting Point, °C | 17.7 | -38 | -3 |
Boiling Point, °C | 175 | 211 | 245 |
Density, g/cm3 at 25°C | 0.95 | 0.954 | 0.963 |
Vapour Pressure, Pa at 25°C | 132 | 33.2 | 4.6 |
Water Solubility, mg/L at 23°C | 0.056 | 0.017 | 0.053 |
Henry’s Law Constant, Pa m3/mol at 25°C | 1,214,000 | 3,342,000 | 14,667 |
Heat of Evaporation, kJ/mol | 44 | 51.4 | – |
What are linear siloxanes?
Linear methyl-siloxanes (linears) are also basic members of the silicone family. L2, L3, L4 and L5 are part of this group. Linears contain repeating units of silicon (Si) and oxygen (O) in a repeating dimethyl-siloxane chain (Me2Si-O-) and as an endgroup e. g. a trimethyl-siloxane unit (Me3Si-O-). E. g. L2 is frequently used as critical building block (endgroup) of the production of a broad range of silicone polymers.
Beyond Chemistry
The silicones industry is at the forefront of research and leading the way in ensuring that different uses of siloxanes are safe and beneficial to the society and the environment
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