Why Can Polydimethylsiloxane Be Used as a Dielectric Material?

Dimethicone/PDMS(polydimethylsiloxane) is an excellent lubricant, anti-vibration and dielectric material and other additives in the chemical industry. Its characteristics are mainly in the following five aspects:

1. High and low temperature resistance of PDMS. The thermal oxidative stability of PDMS is better than mineral oil and vegetable oil. When it is heated in air at 150°C for 1000H, the viscosity increases by about 2%. If heated in isolated natural air, PDMS can withstand hundreds of hours at 300°C.

2. Inter-facial properties of PDMS. PDMS has low surface tension and is very easy to form a film on the surface of the material, so it is an efficient hydrophobic agent, defoaming agent and release agent. The surface tension of silicone oil is related to the viscosity. The surface tension of phenylmethyl silicone oil is slightly higher than that of PDMS, and increases with the increase of phenyl content. PDMS also has high hydrophobicity, thanks to its Lower surface tension. The contact angle between glass plates treated with PDMS and water is 103 degrees, which is similar to the hydrophobicity of paraffin wax. Due to the poor solubility of silicone oil with other substances, it has excellent defoaming agent performance. Not only PDMS is effective, but also some modified silicone oils are effective, so they are used as defoaming agents in coatings, lubricants, detergents and fermentation industries.

3. Solubility of PDMS. Dimethicone is a non-polar substance, easily soluble in non-polar solvents with small solubility parameters, but difficult to dissolve in polar solvents. The solubility of dimethicone increases with increasing phenyl content. The solubility of methylphenyl silicone is similar to that of dimethicone, but the solubility parameters are different. PDMS has greater solubility in air, nitrogen, titanium dioxide, etc. than mineral oil.

4. Material compatibility of PDMS. Silicone oil has no corrosive effect on metals and plastics, and its appearance does not change after long-term immersion, so it is well compatible with other materials.

5. The light transmittance and sound transmission of PDMS. Tests have shown that all visible light can pass through silicone oil. When the wavelength is 280MM, the transmittance reaches 50%; the speed of sound propagation in silicone oil is close to or slightly lower than that in most organic liquids. The sound transmission rate can be accelerated by increasing the molar mass of silicone oil, especially by introducing phenyl groups.