Volume Resistivity

What is the volume resistivity of a polymer?
What is the formula of volume resistivity?
What is the volume resistivity range for different materials?
What is the difference between volume and surface resistance?
What factors affect insulation resistance?
What are the applications of volume resistivity?
Which instrument measures volume resistivity?
What test methods measure volume resistivity?
What are volume resistivity values of several plastics?

What is the volume resistivity of a polymer?

The volume resistivity of a polymer material is its ability to oppose the flow of electric current through a volume of the cubic specimen. The SI unit of volume resistivity is ohm-meter (Ohm-m).

Volume resistivity is also known as:

electrical resistivity,
bulk resistivity,
specific electrical resistance, or
specific volume resistance.

What is the formula of volume resistivity?

Volume resistivity is denoted by the Greek alphabet, rho (ρ). The formula to calculate it is:

ρ = (V/I) x (A/L)

ρ = R x (A/L)
Where,

ρ = volume resistivity (in ohm-m or ohm-cm)
V = voltage (in volts)
I = current (in ampere)
R = electrical resistance (in ohms)
A = cross-sectional area of the material (in square meters)
L = length of the material (in meters)

The lower the resistivity the higher the conductivity

What is the volume resistivity range for different materials?

The volume resistivities for plastics range from 10¹⁰ ohm-cm for cellulose acetate to 10¹⁹ ohm-cm for polystyrene.

Some materials that show volume resistivity:

The range of volume resistivities of different materials is shown in ‘The Resistivity Spectrum’ below.

Source: Plastics Technology Handbook, Fifth Edition
Note:

Below 10⁵ Ohm-cm the material is considered as conductive.
Above 10⁹ Ohm-cm the material is considered as an electrical insulator.
Volume resistivities above 10²¹ Ω-cm (10¹⁹ Ω-m) are of doubtful validity. This is due to the limitations of measuring equipment.

What is the difference between volume and surface resistance?

The insulation resistance of a dielectric is represented by its “volume resistivity” and “surface resistivity”. This always acts in parallel.

Volume Resistance	Surface Resistance
Volume resistance is the resistance to leakage if the electric current passes through the body of the material. It depends largely on the nature of the material.	Surface resistance is the resistance to leakage along the surface of a material. It is a function of surface finish and cleanliness. Surface resistance is reduced by: oil or moisture on the surface and surface roughness *Note*: Smooth or polished surface gives greater surface resistance

What factors affect insulation resistance?

Temperature: The insulation resistance falls off with an increase in temperature. For example, PS has high insulation resistance. It becomes unsatisfactory above 80°C (176°F). Under these conditions, polymers like PTFE and PCTFE are more suitable.

Relative humidity: The insulation resistance falls off with an increase in humidity. Plastics with high water resistance are less affected by high humidities.

Voltage: The longer the application of voltage the higher the volume resistivity.

Presence of fillers: The presence of fillers in the polymer affects the volume resistivity. The type and amount of filler change the volume resistivity.

What are the applications of volume resistivity?

The applications of volume resistivity include:

Designing an insulator for a specific application.
Screening of conductive pastes.
Defining applications for conducting composites.
It is used to check the uniformity of insulating materials. This is with respect to:
- processing, or
- detection of the conductive impurities that affect the quality of the material.

Which instrument measures volume resistivity?

Resistivity meter

It determines the volume resistivity of a material.
It measures the resulting current by applying a known voltage.
This allows the calculation of the material's resistivity.

Four point probe

It determines the resistivity of materials, especially that of thin films.
The four-point probe configuration helps minimize errors caused by contact resistance.
This makes it a precise and accurate method for resistivity measurements.

Source: ScienceDirect

What test methods measure volume resistivity?

The most usual test methods to determine plastics volume resistivity are:

ASTM D257 — It is used to measure the DC resistance of insulating materials. It also measures conductance.

ASTM D4496-04 — It measures the DC resistance of moderately conductive materials. It also measures conductance.

ASTM D991-89(2020) — It determines the volume resistivity of conductive and antistatic products.

IEC 60093:1980 — It measures the volume resistivity of solid electrical insulating materials. It also measures the surface resistivity. This method is partially replaced by:
- IEC 62631-3-2:2015: Part 3-2 — It measures surface resistance and surface resistivity.
- IEC 62631-3-1:2016: Part 3-1 — It measures volume resistance and volume resistivity.

Procedure

In the usual test, a standard-size specimen is placed between two electrodes.
For 60 seconds, a voltage is applied and the resistance is measured.
Volumetric resistivity is then calculated. The apparent value for a 60-second electrification time is given.
A 4-inch disk is preferable as the specimen size for the test.

What are volume resistivity values of several plastics?

Polymer Name	Min Value (10¹⁵ Ohm.cm)	Max Value (10¹⁵ Ohm.cm)
ABS - Acrylonitrile Butadiene Styrene	14.0	16.0
ABS Flame Retardant	14.0	15.0
ABS High Heat	16.0	16.0
ABS High Impact	16.0	16.0
ABS/PC Blend - Acrylonitrile Butadiene Styrene/Polycarbonate Blend	14.0	17.0
ABS/PC Blend 20% Glass Fiber	16.0	17.0
ABS/PC Flame Retardant	16.0	17.0
ASA - Acrylonitrile Styrene Acrylate	14.0	15.0
ASA/PC Blend - Acrylonitrile Styrene Acrylate/Polycarbonate Blend	13.05	15.0
ASA/PC Flame Retardant	14.0	14.0
CA - Cellulose Acetate	12.0	12.0
CAB - Cellulose Acetate Butyrate	13.0	13.0
CP - Cellulose Proprionate	11.0	11.0
COC - Cyclic Olefin Copolymer	14.0	15.0
CPVC - Chlorinated Polyvinyl Chloride	15.0	16.0
ECTFE - Ethylene ChloroTriFluoroEthylene	16.0	16.0
ETFE - Ethylene Tetrafluoroethylene	15.0	17.0
EVA - Ethylene Vinyl Acetate	15.0	15.0
EVOH - Ethylene Vinyl Alcohol	12.0	13.0
FEP - Fluorinated Ethylene Propylene	17.0	18.0
HDPE - High Density Polyethylene	16.0	18.0
HIPS - High Impact Polystyrene	16.0	16.0
HIPS Flame Retardant V0	15.0	16.0
Ionomer (Ethylene-Methyl Acrylate Copolymer)	16.0	16.0
LCP - Liquid Crystal Polymer	16.0	16.0
LCP Carbon Fiber-reinforced	-1.0	-8.0
LCP Glass Fiber-reinforced	15.0	15.0
LCP Mineral-filled	12.0	16.0
LDPE - Low Density Polyethylene	0.917	0.940
LLDPE - Linear Low Density Polyethylene	16.0	18.0
MABS - Transparent Acrylonitrile Butadiene Styrene	13.0	14.0
PA 46 - Polyamide 46	15.0	15.0
PA 46, 30% Glass Fiber	10.0	13.0
PA 6 - Polyamide 6	14.0	14.0
PA 6-10 - Polyamide 6-10	14.0	14.0
PA 66 - Polyamide 6-6	14.0	14.0
PA 66, 30% Glass Fiber	13.0	13.0
PA 66, 30% Mineral filled	12.0	15.0
PA 66, Impact Modified, 15-30% Glass Fiber	12.0	13.0
PA 66, Impact Modified	11.0	15.0
PAI - Polyamide-Imide	12.0	17.0
PAI, 30% Glass Fiber	14.0	17.0
PAR - Polyarylate	16.0	17.0
PARA (Polyarylamide), 30-60% glass fiber	15.0	15.0
PBT - Polybutylene Terephthalate	14.0	17.0
PBT, 30% Glass Fiber	16.0	16.0
PC (Polycarbonate) 20-40% Glass Fiber	15.0	16.0
PC (Polycarbonate) 20-40% Glass Fiber Flame Retardant	15.0	17.0
PC - Polycarbonate, high heat	15.0	16.0
PC/PBT Blend - Polycarbonate/Polybutylene Terephthalate Blend	16.0	17.0
PC/PBT blend, Glass Filled	15.0	16.0
PCTFE - Polymonochlorotrifluoroethylene	14.0	15.0
PE - Polyethylene 30% Glass Fiber	16.0	16.0
PEEK - Polyetheretherketone	16.0	17.0
PEEK 30% Carbon Fiber-reinforced	1.0	8.0
PEEK 30% Glass Fiber-reinforced	15.0	16.0
PEI - Polyetherimide	5.0	18.0
PEI, 30% Glass Fiber-reinforced	15.0	16.0
PEKK (Polyetherketoneketone), Low Crystallinity Grade	1.0	1.0
PESU - Polyethersulfone	15.0	17.0
PESU 10-30% glass fiber	15.0	16.0
PET - Polyethylene Terephthalate	16.0	16.0
PET, 30% Glass Fiber-reinforced	15.0	16.0
PET, 30/35% Glass Fiber-reinforced, Impact Modified	0.0	2.0
PFA - Perfluoroalkoxy	16.0	18.0
PGA - Polyglycolides	1.400	1.600
PI - Polyimide	14.0	18.0
PMMA - Polymethylmethacrylate/Acrylic	14.0	16.0
PMMA (Acrylic) High Heat	15.0	15.0
PMMA (Acrylic) Impact Modified	14.0	16.0
PMP - Polymethylpentene	16.0	18.0
PMP 30% Glass Fiber-reinforced	16.0	17.0
PMP Mineral Filled	16.0	16.0
POM - Polyoxymethylene (Acetal)	14.0	15.0
POM (Acetal) Impact Modified	15.0	16.0
POM (Acetal) Low Friction	15.0	16.0
PP - Polypropylene 10-20% Glass Fiber	16.0	17.0
PP, 10-40% Mineral Filled	16.0	17.0
PP, 10-40% Talc Filled	16.0	17.0
PP, 30-40% Glass Fiber-reinforced	16.0	17.0
PP (Polypropylene) Copolymer	16.0	18.0
PP (Polypropylene) Homopolymer	16.0	18.0
PP, Impact Modified	16.0	18.0
PPA - Polyphthalamide	15.0	15.0
PPA, 30% Mineral-filled	14.0	16.0
PPA, 33% Glass Fiber-reinforced – High Flow	14.0	16.0
PPA, 45% Glass Fiber-reinforced	14.0	16.0
PPE - Polyphenylene Ether	15.0	16.0
PPE, 30% Glass Fiber-reinforced	15.0	16.0
PPE, Flame Retardant	15.0	16.0
PPS - Polyphenylene Sulfide	15.0	16.0
PPS, 20-30% Glass Fiber-reinforced	16.0	16.0
PPS, 40% Glass Fiber-reinforced	16.0	16.0
PPS, Conductive	1.0	3.0
PPS, Glass fiber & Mineral-filled	15.0	16.0
PPSU - Polyphenylene Sulfone	14.0	16.0
PS (Polystyrene) 30% glass fiber	16.0	16.0
PS (Polystyrene) Crystal	16.0	17.0
PS, High Heat	16.0	16.0
PSU - Polysulfone	15.0	17.0
PSU, 30% Glass finer-reinforced	15.0	16.0
PSU Mineral Filled	16.0	16.0
PTFE - Polytetrafluoroethylene	17.0	18.0
PTFE, 25% Glass Fiber-reinforced	16.0	18.0
PVC (Polyvinyl Chloride), 20% Glass Fiber-reinforced	15.0	16.0
PVC, Plasticized	10.0	16.0
PVC, Plasticized Filled	10.0	16.0
PVC Rigid	15.0	16.0
PVDC - Polyvinylidene Chloride	15.0	16.0
PVDF - Polyvinylidene Fluoride	5.0	14.0
SAN - Styrene Acrylonitrile	16.0	16.0
SAN, 20% Glass Fiber-reinforced	15.0	17.0
SMA - Styrene Maleic Anhydride	16.0	16.0
SMA, 20% Glass Fiber-reinforced	15.0	15.0
SMMA - Styrene Methyl Methacrylate	15.0	15.0
UHMWPE - Ultra High Molecular Weight Polyethylene	16.0	17.0

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