The difference between dimethyl silicone oil and ordinary silicone oil is mainly reflected in chemical structure, physical properties, application fields and functionality. The following is a detailed comparison from multiple dimensions:
1. Chemical structure and composition
Dimethyl silicone oil: It is the most basic variety of silicone oil. Its chemical name is polydimethylsiloxane (PDMS). Its main chain is composed of alternating silicon (Si) and oxygen (O) atoms, and all side chains are methyl (-CH₃). The structural formula is:
PDMS structure
Its viscosity range is usually 0.65~100,000 cSt (centistokes), and the performance is adjusted according to the degree of polymerization.
Ordinary silicone oil: It is a broad term that refers to polymers with siloxane as the main chain, which may contain other modified groups (such as phenyl, amino, epoxy, etc.). For example:
Phenyl silicone oil: The side chain contains benzene rings and has better high temperature resistance.
Amino silicone oil: Contains amino groups (-NH₂), used in fabric softeners.
Fluorosilicone oil: Contains fluorine atoms and has both oil resistance and solvent resistance.
Difference: Dimethyl silicone oil is a subcategory of ordinary silicone oil. Ordinary silicone oil can have more special functions through modification.
2. Comparison of physical properties
Characteristics Dimethyl silicone oil Other common silicone oils (such as phenyl silicone oil)
Temperature range -50℃~200℃ (short term 250℃) Phenyl silicone oil can reach -70℃~300℃
Refractive index About 1.40 (low) Phenyl silicone oil can reach 1.50 (high transparency)
Surface tension About 21 mN/m (very low) It may be higher or lower after modification
Compatibility Poor compatibility with organic solvents Fluorosilicone oil is resistant to oil and solvents
3. Differences in application areas
Dimethyl silicone oil:
Lubricant: used for plastic gears, medical devices (such as syringe lubrication).
Defoamer: food industry (FDA certification level), fermentation industry.
Cosmetics: refreshing skin feel, used as a film-forming agent for skin care products.
Modified silicone oil (ordinary silicone oil):
Phenyl silicone oil: high-temperature thermal oil, LED packaging glue (UV resistance).
Amino silicone oil: shampoo, fabric softener (strong adsorption).
Epoxy silicone oil: coating leveling agent, electronic component packaging.
4. Functional differences
Dimethyl silicone oil: Advantages are chemical inertness, low toxicity and wide viscosity range, but single function.
Modified silicone oil: By introducing special groups to achieve:
Hydrophilicity (such as polyether modified silicone oil).
Adhesiveness (such as epoxy modified silicone oil).
Antistatic properties (such as quaternary ammonium salt modified silicone oil).
5. Price and market
The price of dimethyl silicone oil is relatively low (industrial grade is about 30-50 yuan/kg), while the price of modified silicone oil may double (such as amino silicone oil is more than 100 yuan/kg).
Summary
Dimethyl silicone oil is the "basic model" of the silicone oil family and is suitable for general scenarios; ordinary silicone oil can be expanded to high-end fields (such as aerospace and electronic packaging) through chemical modification. When choosing, you need to weigh the requirements of temperature resistance, compatibility, cost, etc.
