Plastic Material Surface Resistivity And Test Methods

What is surface resistivity
Surface resistivity is used to measure the ease of charge movement or current flow on the surface of the material, the unit expressed in ohms (Ω).

In the plane of the solid material placed two length L, distance d parallel electrodes, two electrodes between the material surface resistance Rs and the distance d is proportional to the electrode length L is inversely proportional to the formula Rs = ρs * d / L that the surface resistivity ρs is the direction of the current through the surface of the material is parallel to the direction of the potential gradient and the surface of the unit width of the ratio of the current.

Surface resistivity is related to the surface properties of the material, and with the surrounding gas medium temperature, relative humidity and other factors have great changes, is a measure of the conductivity of the material is one of the important physical properties.

Materials according to the surface resistivity classification

The surface resistivity of different materials varies greatly, and the surface resistivity usually shows an exponential growth, so the surface resistivity of the material is usually expressed using the nth power of 10, that is, multiplying the number 10 by n. The surface resistivity of the material is usually expressed using the nth power of 10, that is, multiplying the number 10 by itself. For example, metal materials usually have a low surface resistivity (10 negative 8 times Ω or so), while ordinary polymer plastic materials have a high surface resistivity (usually 10 12 times Ω or more).

Insulation: the surface resistivity of the material 10 of the 12th power Ω or more, under the action of DC voltage, the charge inside the material is basically not flowing, non-conductive or conductive very little. Such as air, various mineral oils, vegetable oils, synthetic oils, polymer plastics, inorganic materials (glass, glass fiber, mica, ceramics, asbestos, etc.).

Antistatic plastics: the surface resistivity of the material is between 10 of 11-12 times Ω. Static electricity declines at a slow rate of 0.01 seconds to a few seconds, which prevents electric breakdown, electric sparks or electrostatic adsorption. Such as some of the short-lived dust anti-static film.

Static dissipative plastic: the surface resistivity of the material is between 10 of 6-12 times Ω, the charge to milliseconds (0.001) for the unit of decay rate, faster than the Antistatic Material dissipation or decay rate. Such as anti-static semiconductor carrier tray, explosion-proof electronic and electrical products shell, anti-static textile equipment accessories.

Conductive plastics: the surface resistivity of the material is between 10's 0-5 times Ω. The decay rate of the charge in nanoseconds can provide a grounding path, and the conductivity of the charge is strong enough to release a stronger charge.

Electromagnetic shielding plastics: the surface resistivity of the material is between 10's 0-3rd Ω, the conduction rate of the charge is faster, and the electromagnetic wave attenuates very quickly in a good conductor, so highly conductive plastic materials can also be used for absorbing or reflecting electromagnetic energy and shielding the source of interference. Electromagnetic shielding plastics are commonly used for EMI/RFI shielding, and high conductivity can also be used for electrodes, low-temperature heaters, and so on.

Conductor: the surface resistivity of the material is very small and easy to conduct current, under the action of the external electric field, there are a large number of freely movable charged particles in the conductor for directional movement, can form a significant current. Common conductors are metals and carbon compounds (graphite, carbon black, carbon fiber, carbon nanotubes, etc.)

Antistatic: Static electricity declines at a slow rate of 0.01 seconds to several seconds, preventing electrical breakdown, electrical sparks, or electrical adsorption.

Static Dissipation: Decay rate in milliseconds (0.001), faster dissipation or decay rate than anti-static materials.

Conductive: Decay rates in nanoseconds provide a path to ground and release a stronger charge.

EMI/EFI Shielding: absorbs or reflects electromagnetic energy and shields against sources of interference. Usually measured by volume resistivity.

Surface resistivity test method

HONY Plastic usually uses a Parallel Probe Surface Resistivity Meter to test the surface resistivity of plastic materials.

The Parallel Probe ResistivityMethod is a fast and convenient way to measure the surface resistivity of flat, uniform materials in accordance with the EOS/ESD-S11.11-1993 standard.

Requirements of the object to be tested: the surface is flat and the size width is more than 60mm.

The test steps are as follows:

1. Place the tested sample on the insulating mat.

2. Place the tester on the surface of the tested sample.

3. Set the voltage switch to the desired voltage position (10 volts or 100 volts). (Some simpler testers do not have a voltage switch.)

4. Press the measurement button continuously with a pressure of about 2.5 kg to read the surface resistivity (depending on the accuracy of the tester, some can only read values of the order of 10), temperature, and relative humidity (depending on the accuracy of the tester, some cannot be read), and the entire measurement process will take about fifteen seconds.

For larger or smaller sizes where parallel probes cannot be used, testing can also be done by using different forms of electrodes such as pincers, concentric rings, weights, and two points.

HONY Plastic R & D and production of conductive anti-static electromagnetic shielding plastic conductive fillers include: carbon fiber, carbon black, carbon nanotubes, graphite, polymer long-lasting antistatic masterbatch, low molecular antistatic agent, stainless steel fibers, iron powder and so on. Plastic substrates include: PP , PE , PVC , PS, ABS, PMMA, PC , PA, POM, POK, PBT, PET , PPO, PPS, LCP, PEI , PPSU, PEEK, PTFE, FEP, ETFE, PVDF, PFA, TPU, TPE, TPEE, TPV, POE, EVA and so on. And can be customized according to customer requirements of different conductivity coefficients, different mechanical strength, different flame retardant properties of conductive anti-static electromagnetic shielding plastic, Qifu conductive anti-static electromagnetic shielding plastic materials are designed to protect products and components to avoid static adsorption interference, from the hazards of electrostatic discharge, shielding of electromagnetic radio frequency signals, and can be effective and controlled in the products to conduct current.