The need to differentiate Anti Static Materials
Static electricity like its name is electricity at rest. Whenever a sliding, rubbing, or separating of a material (for example: plastics, fiber glass, rubber, textiles, ect) happens will generate electrostatic voltages. The electrical charge is the transference of these electrons and under some special situation, one charge can reach 30,000 to 40,000 volts.
If the above things happens to an insulating material, like plastic, the charge tends to remain in the localized area of contact. This electrostatic voltage may then discharge via an arc or spark when the plastic material comes in contact with a sufficiently different potential body like a person or microcircuit. This is called Electrostatic Discharge (ESD) and you must beware of its effect:
To a person, the results may range anywhere from a mild to a painful shock. But in extreme cases of ESD that create Sparks or Arc Flash in flammable liquids, solids or gasses such as a hospital operating rooms or explosive device assembly can lead to extreme damaged, even loss of life.
It only takes 20 electrostatic volts to irreparably damage an integrated circuit
Micro-electronic parts can be destroyed or damaged by ESD as low as 20 volts. Since people are prime causes of ESD, they often cause damage to sensitive electronic parts, especially during manufacturing and assembly. The consequences of discharge through an electrical component sensitive to ESD can range from erroneous readings to permanent damage resulting in excessive equipment downtime and costly repair or total part replacement.
Anti Static Materials
For ESD control purposes, materials are classified by how how strongly a material opposes the flow of electric current. The lower the resistivity, the more readily the material permits the flow of electric charge. At such a certain low value, the more conductive the material and may be considered “Anti Static”. (Note: Although the term is widely used, it is better to avoid it if possible since the term can mean a wide variety of things)
|Classification||Charge Movement||Resistance||Ohms||Is it Anti static?|
|Conductive||Very Fast||Low Resistance||103 – 105||Yes|
|Dissipative||Fast||Medium Resistance||106 – 1010||Yes|
|Insulative||Slow or No Movement||High Resistance||1011 – 1012||No|
The resistance is measured in Ohms and is typically displayed in powers of 10 (example 103)
The following ranges and definitions are found in ESD Association or EIA standards publications:
Conductive materials: With a low electrical resistance, electrons flow easily across the surface or through the bulk of these materials. Charges go to ground or to another conductive object that the material contacts or comes close to. Conductive materials have a surface resistivity less than 1 x 105 Ω/sq or a volume resistivity less than 1 x 10^4 Ω-cm. Conductive materials are classified “Anti static”.
Dissipative materials: For these materials, the charges flow through the material slowly and in a somewhat more controlled manner than with conductive materials. Dissipative materials have a surface resistivity equal to or greater than 1 x 105 Ω/sq but less than 1 x 1012 Ω/sq or a volume resistivity equal to or greater than 1 x 104 Ω-cm but less than 1 x1011 Ω-cm.2. Dissipative materials are also classified “Anti static” material with high resistance should be watched and maintain carefully.
Insulative materials: Insulative materials prevent or limit the flow of electrons across their surface or through their volume. Insulative materials have a high electrical resistance and are difficult to ground. Static charges remain in place on these materials for a very long time. Insulative materials are defined as those having a surface resistivity of at least 1 x 1012 Ω/sq or a volume resistivity of at least 1 x 1011 Ω-cm. Insulative materials are not classified as “Anti Static”.
Anti-Static: Is a term used to describe materials that prevent the buildup of static electricity. Both conductive and dissipative materials are classified as Anti Static. Insulative materials are not (!).
|Sea water||2×10−1||Drinking water||2×101 – 2×103|
|Glass||10×1010 – 10×1014||Hard rubber||1×1013|
|Wood (oven dry)||1×1014 – 16||Air||1.3×1016 – 3.3×1016|
|PET||10×1020||Teflon||10×1022 – 10×1024|
Measurement (Ω•m) of some common Materials at 20 °C Resistivity
Anti Static Casters
Firstly, Anti static Casters are not Electrical Insulative Casters. They should be either Conductive or Dissipative. Through studying, the resistant range of the casters should be 103 – 109 Ω/sq. According to our manufacturers, the Conductive Rubber Casters are widely used because Low Resistance will free the Static Electric much faster and smoother.
For more details about our Anti Static Casters, please visit:
- Anti Static Casters: Black Conductive Rubber
- UPDATE: From 18/11/2017 – check Anti Static Casters: Gray Conductive Rubber