Ordinary silicone itself is not anti-static. On the contrary, it is a good insulator and is prone to generating and accumulating static electricity. However, silicone can be endowed with anti-static or conductive properties through special modification techniques.
1. Why is ordinary silicone not anti-static?
Chemical structure determines properties: The main chain of silica gel is a stable structure composed of alternating silicon (Si) and oxygen (O) atoms, while the side chains are usually inert methyl groups (-CH₃) or vinyl groups (-CH=CH₂). This molecular structure is very stable and has no freely movable electrons or ions.
High resistivity: It is precisely because of the absence of charge carriers that the volume resistivity of pure silica gel is extremely high, typically ranging from 10¹² to 10¹⁵ Ω·cm. This number indicates that it conducts almost no electricity and is an excellent insulating material.
Risk of static electricity accumulation: Due to its excellent insulation property, when silicone products rub against, come into contact with or separate from other materials such as plastic or fabric, the generated charges cannot be conducted away by themselves and will accumulate on the surface, forming static electricity. This is very dangerous in some application scenarios.
2. How to make silicone have anti-static/conductive properties?
In order to enable silicone to be used in environments sensitive to static electricity, it is necessary to create channels for charge movement through physical modification methods.
The main methods are as follows:
a) Adding conductive fillers (the most mainstream and effective method) :
Uniformly mix conductive substances in a certain proportion into the silica gel matrix to form a conductive network.
Carbon-based fillers: such as Carbon Black, carbon nanotubes (CNTs), graphene. Carbon black is the most commonly used and cost-effective option, which can be formulated into different grades ranging from anti-static to conductive. The drawback is that it is usually only made black. Metal fillers: such as silver powder (Ag), silver-coated copper powder, nickel powder, etc. Metal fillers have excellent electrical conductivity, but they are very expensive and are usually used in fields with extremely high electromagnetic shielding (EMI) requirements.
Surface coating: Nickel plating, gold plating and other treatments are carried out on the surface of the formed silicone products to endow them with a metal conductive layer. This method is costly and there is a risk of the coating peeling off.
b) Add permanent antistatic agents (ionic type)
Mix special ionic antistatic agents into the silica gel. These additives will migrate to the surface of the products, absorb moisture from the air and form a thin water film. Water molecules can ionize into ions, thereby dissipating static electricity through the mechanism of moisture absorption and conduction.
Advantages: It can be mixed into various colors (unlike carbon black which can only be black), and has a relatively small impact on the original mechanical properties of the base material. Disadvantage: The antistatic effect depends on the environmental humidity. The effect will be greatly reduced in a very dry environment, such as indoors in the north during winter.