What is Dimethicone (Polydimethylsiloxane PDMS)? Dimethicone is the INCI designation for linear polydimethylsiloxane (PDMS) – a chemically inert, transparent liquid polymer with low surface tension, high thermal stability and excellent water repellency. Properties of Silicone Oil (PDMS) ✓ Wide temperature range (low viscosity change compared to mineral oils) ✓ Water-repellent...
Silicone Oil - Dimethicone (Polydimethylsiloxane PDMS)
What is Dimethicone (Polydimethylsiloxane PDMS)?
Dimethicone is the INCI designation for linear polydimethylsiloxane (PDMS) – a chemically inert, transparent liquid polymer with low surface tension, high thermal stability and excellent water repellency.
Properties of Silicone Oil (PDMS)
- ✓ Wide temperature range (low viscosity change compared to mineral oils)
- ✓ Water-repellent and chemically inert
- ✓ Good dielectric properties (insulation)
- ✓ Low surface tension – excellent spreading/lubrication
- ✓ Low pour point – remains liquid in the cold
⚠️Important Quality Information
Please note: If the oil quality isn't explicitly stated, we supply industrial-grade silicone oil. If you're interested in food-grade, pharmaceutical-grade, or medical-grade silicone oil, please feel free to contact us.
Silicones come in four grades: Industrial silicone oil, cosmetic silicone with the INCI name dimethicone, pharmaceutical silicone also with the INCI name dimethicone, often with the addition "EP" or "extra pure," and silicones tested for suitability for use in food contact applications, such as silicone molds for food or coating disposable plates, etc.
Basic information
Silicone oil in the form of polydimethylsiloxanes without active/crosslinking components is a basic product for many polycondensation silicones.
The oil is used to make the silicone more fluid, softer, more flexible and more stretchable.
Sustainability
Silicone oils are not extracted from petroleum, but made from silicon, the most common element in the earth's crust.
Excellent Features
Thermal Stability
Minimal change in physical properties over a wide temperature range
Water-repellent
Excellent water-repellent properties
Electrical Insulation
Good dielectric properties
Surface activity
Low surface tension and high chemical reactivity
Low Pour Point
Remains liquid at low temperatures
Solubility
Good solubility in a wide range of solvents
⚠️Important Usage Information
This can be used in both polycondensation silicones and addition silicones.
Because oil doesn't cross-link in the silicone elastomer, it can migrate to the surface over time and under mechanical stress. This causes the silicone to lose mass and can cause shrinkage.
Professional Silicone Oil
Discover our range of polydimethylsiloxanes and dimethicones for all industrial applications. From heat baths to electrical insulation, we have the right viscosity for your application.
📊 Technical Specifications
🌡️ Viscosity vs. Temperature
Silicone oil is relatively stable over a wide temperature range. Here's a graph of the viscosity (stickiness) versus temperature of silicone oil:
📋 Properties by Viscosity
Here is an overview of average properties of silicone oil per available viscosity:
Heat Transfer & Heat Bath Applications
Why Silicone Oil for Hot Tubs?
Silicone oil for heat baths and heat transfer: safe, stable, and efficient. Silicone oil is an excellent choice as a heat transfer fluid in applications such as heat baths, thermal circulation pumps, and industrial heating systems.
The unique thermal and chemical properties of silicone oil make it a reliable alternative to mineral oils or synthetic heat transfer fluids.
High Thermal Stability
Can withstand temperatures well above 200°C for short periods
Low Viscosity in Cold
Remains liquid below freezing point
Electrical Insulation
Ideal for electrical components
Important Points to Consider When Using Hot Tubs
1. Choose the Correct Viscosity and Flashpoint
For proper functioning of your heat bath or pump it is important to choose a silicone oil that:
- Liquid enough at the desired operating temperature
- Has a flash point (flammability temperature) that is well above the maximum operating temperature
2. Thermal Aging with Long-Term Use
Although standard silicone oil can withstand high temperatures, it is not suitable for prolonged exposure to temperatures above 180°C. Prolonged heating can produce decomposition products:
Decomposition products:
- Siloxanes and methane-like gases
- D3 and D4 in a nitrogen-rich environment
- Oxidation products in open systems
Implications:
- Loss of viscosity
- Poorer heat transfer
- Pollution of the system
3. Phenyl-modified High Temperature Silicone Oil
For applications where you work continuously above 180°C, it is strongly recommended to use a phenyl-modified silicone oil:
- Thermally more stable
- Less sensitive to oxidation
- Long-term usability without significant degradation
Typical Applications
Laboratory Heat Baths
Industrial Heating Mantles
Heat exchangers
Electronic Component Cooling
Technical Formulas & Specifications
Expansion coefficient
While we don't have exact coefficient of expansion measurements for silicones of different viscosities versus temperature, this general formula can give you an idea of what to expect:
γ = 1/V ∂V/∂T
where: γ (gamma) = cubic expansion coefficient (K⁻¹), V = volume (m³), T = temperature (K)
Dielectric Constant (1000 cSt)
Influencing Factors:
- Viscosity: Higher viscosities (1000 cSt) often have a slightly higher dielectric constant than thinner oils (100 cSt)
- Polymer structure: Linear PDMS is standard; phenyl groups can increase value
- Purity: Additives or contaminants may affect the value
Conclusion & Recommendations
Silicone oil is a versatile and safe choice for heat transfer, provided you choose the right variant for your temperature and usage profile.
Up to 150-180°C:
Regular silicone oil is sufficient
Above 180°C:
Phenyl-modified variant essential