Polydimethylsiloxane (PDMS)

Polydimethylsiloxane (PDMS), also known as dimethyl silicone oil, is an elastic polymer with the chemical formula C₃H₉SiO(C₂H₆SiO)ₙSiC₃H₉ (n > 2). It is typically a colorless, transparent liquid with almost no odor. PDMS exhibits excellent electrical insulation properties, thermal stability, water repellency, low volatility, minimal vapor pressure, a small viscosity-temperature coefficient, high compressibility, and low surface tension. 

It is widely used in lubrication, damping, shock absorption, dust prevention, dielectric fluids, and mold release applications. It also serves as an additive in coatings and skin ointments. In the medical field, PDMS-treated gauze and cotton for wound dressing do not adhere to injuries, reducing patient discomfort. 

Applications:

1. Cosmetics

   Due to its low surface tension, easy spreadability, and adjustable viscosity, PDMS imparts a smooth, non-greasy feel to personal care products, softening the skin. It acts as an antifoaming and defoaming agent, preventing the "whitening" effect during application. Different viscosities are selected for varying needs—higher viscosity provides more oiliness, while lower viscosity delivers a dry feel. Its low deposition rate limits its usage in formulations. Blending different viscosity grades of PDMS can fine-tune product performance. 

2. Electronics

   PDMS is used in electrical connectors and other components in the electronics industry. 

3. Textiles & Leather

   As a water repellent, softening agent, and hand-feel modifier, PDMS is applied to fibers and leather. It also functions as a defoamer in dyeing and a lubricant for sewing threads. In leather fatliquoring, it enhances hydrophobicity, softness, and comfort. Surface treatment improves wear resistance, waterproofing, and mold release. 

4. Polishing Agents 

   PDMS is an effective ingredient in polishes for automobiles, furniture, footwear, and cement products (car wax, foam furniture cleaners, vinyl roof cleaners). It delivers optimal results with minimal usage. 

5. Mold Release Agent 

   As a release agent for rubber/plastic products (brake pads, screws, plugs) and EVA shoe materials, PDMS can be used directly or diluted 10–200 times with soft water. It is highly efficient, stable, and versatile. 

6. Lubricant

   PDMS serves as a lubricant for extruded rubber products like conveyor belts. It is also used in textile processes (yarn weaving, sewing thread lubrication, hosiery/underwear production, needle lubrication) and glass fiber filtration.