Explaining Silicone Viscosities
One of the most commonly asked question, regarding the Pure Silicone Fluids, is “what separates one viscosity from the next?” Fortunately, the answer is simple. Pure Silicone Fluids are 100% Polydimethylsiloxane / PDMS Silicone oils with viscosity measured @ 25C. They are linear in nature. As the chains get longer, viscosity increases. The length of the chain is reflected in the molecular weight, which increases along with the viscosity. See Polydimethylsiloxane Properties Chart which shows the MW in the last column.
Higher viscosities are obtained by further processing. The processing elongates the silicone chain. Even though the silicone chain is elongated and viscosities increase, the properties change little for viscosities > 100cSt.
For lower viscosities, especially below 5cSt, this is not the case. The viscosities <5cSt are characterized by their low flash points, high rate of volatility and low surface tensions. They behave more like solvents than conventional PDMS Silicone oils.