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Conductive Carbon Filled PTFE

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The insulating properties of PTFE limit its application in many situations where electrical conductivity is required. By filling the conductive filler to change the conductive behavior of PTFE and adjust the interface bonding performance between the filler and the matrix, a high-performance PTFE conductive composite material can be obtained.

The advantages and disadvantages of common conductive carbon

Commonly used conductive fillers for PTFE are mainly carbon black, carbon nanotubes, carbon fibers, graphite, graphene, copper powder, silver powder, etc. Conductive composite materials prepared from traditional conductive fillers, such as carbon fiber (CF) and graphite, have the advantages of low price and a wide range of raw materials.

Carbon

  • Carbon (powder or fiber) can impart excellent compressibility (low deformation under load) and wear resistance, good thermal conductivity (heat dissipation) and low permeability. Carbon-filled PTFE compounds are not as abrasive as glass-filled compounds, but they are still more abrasive than polymer-filled compounds. When combined with graphite, the carbon-filled compound has excellent wear resistance and friction properties. Carbon fiber has better creep resistance than carbon powder, but fiber is more expensive.
  • Variation of conductivity at 1 Hz of PTFE composites with respect to carbon black filler loadingFigure 1. Variation of conductivity at 1 Hz of PTFE composites with respect to carbon black filler loading [1]

Graphite

  • Graphite is a crystal modification of high-purity carbon. Its sheet-like structure imparts excellent lubricity and reduced wear. Graphite is usually used in combination with other fillers (especially carbon and glass). However, the disadvantage of graphite is that the amount of conductive filler is large, which will affect the processing and mechanical properties of the material.

Carbon Nanotubes

  • Carbon nanotubes (CNT) filled with PTFE can improve the conductivity of composite materials, but the cost of modification with CNT is higher.

The electrical conductivity of the CNT-filled PTFE filmFigure 2. The electrical conductivity of the CNT-filled PTFE film [2]

Graphene

  • Graphene has many unique physical and chemical properties. Graphene is a substance with no energy gap and shows metallicity. In single-layer graphene, each carbon atom has an unbonded electron, so it has very good electrical conductivity. However, graphene is prone to agglomeration in practical applications, and group gatherings affect its performance.

Properties of conductive carbon filled PTFE

Physical PropertiesMetricComments
Density1.90 - 2.19 g/ccAverage value: 2.10 g/cc
Linear Mold Shrinkage0.014 - 0.045 cm/cmAverage value: 0.0240 cm/cm
Mechanical PropertiesMetricComments
Hardness, Shore D52 - 70Average value: 63.3
Tensile Strength, Ultimate8.00 - 39.0 MPaAverage value: 17.9 MPa
Elongation at Break30 - 350 %Average value: 161 %
Compressive Yield Strength7.00 - 23.4 MPaAverage value: 11.7 MPa
Shear Strength14.479 - 19.3053 MPa
@Temperature 26.7 - 149 °C
Average value: 16.9 MPa
Coefficient of Friction0.060 - 0.24Average value: 0.0977
Coefficient of Friction, Static0.050 - 0.20Average value: 0.0913
K (wear) Factor12.0 - 60.4 x 10-8 mm³/N-MAverage value: 26.4 x 10-8 mm³/N-M
Electrical PropertiesMetricComments
Electrical Resistivity1000 - 1.00e+11 ohm-cmAverage value: 1.25e+10 ohm-cm
Surface Resistance1000 - 1.00e+12 ohmAverage value: 3.33e+11 ohm
Thermal PropertiesMetricComments
CTE, linear65.0 - 160 µm/m-°CAverage value: 121 µm/m-°C
Thermal Conductivity0.590 - 0.800 W/m-KAverage value: 0.643 W/m-K
Maximum Service Temperature, Air260 - 300 °CAverage value: 263 °C
Minimum Service Temperature, Air-200 °CAverage value: -200 °C

Note: The comments report the average value and are for customer reference only.

References

  1. Shijie Zhang, Qiuying Li, Yanchao Che, Chifei Wu, Weihong Guo, Chinese Journal of Materials Research 31 (2017) 847-852.
  2. Yoshiyuki Show, Hironori Itabashi, Diamond & Related Materials 17 (2008) 602–605.
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