Polydimethylsiloxane (PDMS)

About This Product

Polydimethylsiloxane, PDMS with CAS number 63148-62-9, is supplied as a clear, odourless fluid across an enormous viscosity range, from a few centistokes to over a million. Its backbone is alternating silicon and oxygen atoms with methyl groups attached, rather than the carbon chain of an organic polymer. That difference in backbone accounts for nearly everything unusual about it. The silicon-oxygen bond is considerably stronger than carbon-carbon and is not attacked by oxygen in the same way, so PDMS is stable from below minus 50 to above 200 degrees Celsius where a hydrocarbon oil would oxidise and char. The bond is also unusually flexible, and the chain rotates freely, which is why silicone fluids show a remarkably flat viscosity-temperature curve: they thin far less on heating than mineral oils, making them useful as damping and hydraulic fluids across wide temperature swings. The methyl groups pointing outward give a very low surface tension, which is why PDMS spreads spontaneously across surfaces, releases moulded parts, and breaks foam by destabilising the liquid films between bubbles. It is used as an antifoam, in release agents and mould lubricants, personal care and hair conditioning, damping and hydraulic fluids, water repellents and in electrical insulation. Bio Green Chem supplies PDMS grades to specification on viscosity, volatiles, refractive index, flash point, acidity and appearance.