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Dielectric Strength of Plastics | Electrical Properties of Plastics | The Definitive Guide

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Hello people; I hope you’re all doing fantastic. Today, I will share a very engaging piece on plastics’ dielectric strength and dielectric properties. So without further ado, let’s get started.

Dielectric Strength of Plastics 

The dielectric strength of most plastics typically falls between 100 and 300 kV/cm, averaging at about 200 kV/cm. In contrast, specific chlorinated and additive-enriched polymers showcase dielectric strengths as high as 500 kV/cm. Teflon, renowned for its outstanding chemical and impact resistance, can achieve a remarkable 700 kV/cm.

Most plastics are poor conductors of electricity and resist a current flow, thus called dielectrics or insulators. That is one of the most valuable properties of plastic material and makes them applicable in making products utilized in our day-to-day lives, such as switches & switchboards, wire coatings, light fittings, and other electrical goods and appliances.

As plastics are insulators, when voltage is applied and steadily increased on them, It will eventually reach a point when the electrical properties break down—the breakdown increases an electrical arc across the electrodes, which causes a catastrophic reduction in resistance.

What is Dielectric Strength? 

The dielectric strength of plastics or any insulating material can be understood as the ratio of the charge deposited in an insulating material between two metallic plates to the charge stored when a vacuum or air replaces the insulating material. The phenomenon is called electrical permittivity. The dielectric strength of a material showcases its ability to store electrical energy.

The dielectric strength of plastic depends on its type and shape, the field increase rate, and the medium surrounding the insulator. Dielectric strength is derived by a unit kV by mm of thickness.

Which Common Standard Tests Determine Dielectric Strength?

The primary standard tests typically employed to determine dielectric strength include:

ASTM D149-20: This test method gauges the dielectric breakdown voltage and the dielectric strength of insulation materials, such as electrical cables and wires.

IEC 60243-1:2013: This method is employed to ascertain the dielectric strength of solid insulation materials, like plastics and rubbers.

How to Calculate Dielectric Strength?

The most common standard tests to calculate the dielectric strength of plastic materials are ASTM D149 or IEC 60243-1. Below are the methods used for measuring dielectric strength:

  1. Short time method
  2. Slow rate of rise method
  3. Step by step method 

Short Time Method

Here, the voltage is applied across the two electrodes and bumped up constantly at a uniform rate (500 V/sec) until the breakdown occurs. The meaning of breakdown is when the voltage punctures the sample or creates decomposition.

Slow Rate of Rise Method

The voltage is applied to the test electrodes at only 50% of the breakdown voltage until breakdown or decomposition happens.

Step By Step Method

The voltage is applied to the electrodes at a predetermined starting voltage in various steps and spans until the breakdown.

Interesting Read – 7 Best UV Resistant Plastics For Outdoor Applications 

Applications

  • Dielectric material for capacitors used in radio and other electrical equipment.
  • Development of material for energy storage solutions.
  • Used by circuit designers to evaluate different printed-circuit-board (PCB) materials.
  • Thin films in the high-speed digital microprocessor.

Factors Affecting Dielectric Strength 

The graph illustrates the Weibull Characteristic Breakdown Field, measured in MV/m, for four different polymers across a temperature range of 0 to 220°C. The polymers examined are PEI (Polyetherimide), BOPP (Biaxially Oriented Polypropylene), PPS (Polyphenylene Sulfide), and PEEK (Polyether Ether Ketone).

At 0°C, PEI has the highest breakdown field, around 750 MV/m, but it decreases gradually to approximately 600 MV/m by 220°C. BOPP starts at about 725 MV/m and shows a slight dip, stabilizing near 675 MV/m. PPS starts near 600 MV/m, remains relatively steady until 140°C, and then dips to around 550 MV/m by 220°C.

PEEK displays the most notable decline, starting at 400 MV/m and plummeting to slightly above 100 MV/m by the end of the temperature spectrum. Each data point has associated error bars indicating 90% confidence intervals, which showcases the potential variability in measurements.

The data shows that as temperature increases, the breakdown field for these polymers tends to decrease, with PEEK being the most affected by rising temperatures.

  • Hold on tight because things are about to get heated! The dielectric strength of plastics tends to drop as temperatures rise, roughly moving in an inverse relationship to absolute temperature. Yet, it’s fascinating that dielectric strength remains remarkably unaffected by temperature fluctuations.
  • But wait, there’s more! Mechanical stress can significantly impact dielectric strength, as it introduces internal flaws in insulators, creating leakage pathways and weakening their dielectric fortitude.
  • And here’s the twist: manufacturing quirks can significantly affect a plastic’s dielectric strength. Even the tiniest defects can pack a punch from weld lines in injection molding to flow lines in compression molding. These seemingly insignificant imperfections can slash an insulator’s dielectric strength by 30-40%!

Polar VS Non-Polar Plastics 

A plastic material’s dielectric strength and electrical properties heavily depend on its structure. The structure of a polymer decides whether it is polar or non-polar, thereby determining its properties.

Polar polymers (PMMA, PC, Nylon, PVC, etc.) are comprised of dipoles created due to the imbalance in the distribution of electrons. These dipoles align themselves in the presence of the electric field. Thus dipole polarization is designed for the polymer, making them average-performing insulators.

On the other hand, Non-polar polymers (PS, PTFE, PP, PE) have symmetrical molecules and are entirely covalent. There is no presence of polar dipoles in them, and thus the attendance of the electric field doesn’t align with the dipoles. However, the movement of electrons in the direction of the electric field will erupt in a slight electron polarization. These polymers have elevated resistivities and low dielectric constant.

Polar plastics have the propensity to absorb moisture from the atmosphere. Moisture can raise the dielectric constant and lower the resistivity. As the temperature rises, polymer chains move faster, and the dipoles are aligned more quickly.

Non-polar plastics do not affect the rising atmosphere and moisture.

Dielectric Strength Values of Polymers 

Polymer Name
Minimum Value (kV/mm)
Maximum Value (kV/mm)
ABS – Acrylonitrile Butadiene Styrene15.734
ABS Flame Retardant2435.4
ABS High Heat1220
ABS High Impact1220
ABS/PC Blend – Acrylonitrile Butadiene Styrene/Polycarbonate Blend1570
ABS/PC Blend 20% Glass Fiber29.930
Amorphous TPI Blend, Ultra-high heat, Chemical Resistant (Standard Flow)5454
Amorphous TPI, Moderate Heat, Transparent1717
Amorphous TPI, Moderate Heat, Transparent (Food Contact Approved)1717
Amorphous TPI, Moderate Heat, Transparent (Mold Release grade)1414
Amorphous TPI, Moderate Heat, Transparent (Powder form)1717
ASA – Acrylonitrile Styrene Acrylate40105
ASA/PC Blend – Acrylonitrile Styrene Acrylate/Polycarbonate Blend8095
ASA/PC Flame Retardant9090
CA – Cellulose Acetate815
CAB – Cellulose Acetate Butyrate1016
CP – Cellulose Proprionate1218
CPVC – Chlorinated Polyvinyl Chloride5060
ECTFE – Ethylene ChloroTriFluoroEthylene1414
ETFE – Ethylene Tetrafluoroethylene7.877.87
EVA – Ethylene Vinyl Acetate2728
FEP – Fluorinated Ethylene Propylene2279
HDPE – High Density Polyethylene1724
HIPS – High Impact Polystyrene1224
HIPS Flame Retardant V03335
Ionomer (Ethylene-Methyl Acrylate Copolymer)4040
LCP – Liquid Crystal Polymer3239
LCP Glass Fiber-reinforced2230
LCP Mineral-filled2635
LDPE – Low Density Polyethylene1628
MABS – Transparent Acrylonitrile Butadiene Styrene3437
PA 11 – (Polyamide 11) 30% Glass fiber reinforced4040
PA 11, Conductive2455
PA 11, Flexible2455
PA 11, Rigid2455
PA 12 (Polyamide 12), Conductive2455
PA 12, Fiber-reinforced2455
PA 12, Flexible2455
PA 12, Glass Filled2455
PA 12, Rigid2455
PA 46 – Polyamide 461525
PA 46, 30% Glass Fiber2535
PA 6 – Polyamide 61020
PA 6-10 – Polyamide 6-101626
PA 66 – Polyamide 6-62030
PA 66, 30% Glass Fiber2525
PA 66, 30% Mineral filled2530
PA 66, Impact Modified, 15-30% Glass Fiber11.821
PA 66, Impact Modified1890
PA 66, Carbon Fiber, Long, 30% Filler by Weight1.31.3
PAI – Polyamide-Imide23.624
PAI, 30% Glass Fiber27.634
PAR – Polyarylate1717
PARA (Polyarylamide), 30-60% glass fiber23.730
PBT – Polybutylene Terephthalate1530
PBT, 30% Glass Fiber5050
PC (Polycarbonate) 20-40% Glass Fiber2020
PC (Polycarbonate) 20-40% Glass Fiber Flame Retardant1738
PC – Polycarbonate, high heat1635
PCTFE – Polymonochlorotrifluoroethylene2124
PE – Polyethylene 30% Glass Fiber19.719.7
PEEK – Polyetheretherketone2020
PEEK 30% Carbon Fiber-reinforced18.519
PEEK 30% Glass Fiber-reinforced1524
PEI – Polyetherimide2833
PEI, 30% Glass Fiber-reinforced2530
PEI, Mineral Filled2025
PEKK (Polyetherketoneketone), Low Cristallinity Grade23.623.6
PESU – Polyethersulfone1680
PESU 10-30% glass fiber14.640
PET – Polyethylene Terephthalate6060
PET, 30% Glass Fiber-reinforced16.822.5
PETG – Polyethylene Terephthalate Glycol4545
PFA – Perfluoroalkoxy2.12.2
PGA – Polyglycolides3480
PI – Polyimide2227.6
PMMA – Polymethylmethacrylate/Acrylic1522
PMMA (Acrylic) High Heat18.720
PMMA (Acrylic) Impact Modified1560
PMP – Polymethylpentene2830
PMP 30% Glass Fiber-reinforced23.623.6
PMP Mineral Filled23.623.6
POM – Polyoxymethylene (Acetal)13.820
POM (Acetal) Impact Modified1919
POM (Acetal) Low Friction1616
PP – Polypropylene 10-20% Glass Fiber3045
PP, 10-40% Mineral Filled3070
PP, 10-40% Talc Filled3070
PP, 30-40% Glass Fiber-reinforced3045
PP (Polypropylene) Copolymer2028
PP (Polypropylene) Homopolymer2028
PP, Impact Modified2028
PPA – Polyphthalamide20.820.9
PPA, 30% Mineral-filled2022
PPA, 33% Glass Fiber-reinforced2022
PPA, 33% Glass Fiber-reinforced – High Flow1820
PPA, 45% Glass Fiber-reinforced2224
PPE – Polyphenylene Ether2022
PPE, 30% Glass Fiber-reinforced2222
PPE, Flame Retardant1625
PPE, Impact Modified11.1
PPS – Polyphenylene Sulfide1124
PPS, 20-30% Glass Fiber-reinforced13.817
PPS, 40% Glass Fiber-reinforced1717
PPS, Glass fiber & Mineral-filled1313
PPSU – Polyphenylene Sulfone14.220
PS (Polystyrene) 30% glass fiber1519.7
PS (Polystyrene) Crystal1628
PSU – Polysulfone1510
PSU, 30% Glass finer-reinforced16.940
PTFE – Polytetrafluoroethylene1724
PTFE, 25% Glass Fiber-reinforced2020
PVC, Plasticized1030
PVC, Plasticized Filled1030
PVC Rigid1040
PVDF – Polyvinylidene Fluoride1027
SAN – Styrene Acrylonitrile1224
SAN, 20% Glass Fiber-reinforced19.720
SMA – Styrene Maleic Anhydride1616
SMA, 20% Glass Fiber-reinforced2121
SMMA – Styrene Methyl Methacrylate19.719.7
UHMWPE – Ultra High Molecular Weight Polyethylene2828


Engaging Read – What is the Glass Transition Temperature of Plastics?

Dielectric Constant Values of Mainstream Polymers 

Polymer NameMin ValueMax Value
ABS – Acrylonitrile Butadiene Styrene
2.73.2
ABS Flame Retardant
2.83
ABS High Heat2.45
ABS High Impact2.45
ABS/PC Blend – Acrylonitrile Butadiene Styrene/Polycarbonate Blend
2.93.2
ABS/PC Blend 20% Glass Fiber
3.13.2
Amorphous TPI Blend, Ultra-high heat, Chemical Resistant (Standard Flow)
3.53.5
ASA – Acrylonitrile Styrene Acrylate
3.33.8
ASA/PC Blend – Acrylonitrile Styrene Acrylate/Polycarbonate Blend
33.4
ASA/PC Flame Retardant
3.23.2
CA – Cellulose Acetate
38
CAB – Cellulose Acetate Butyrate
37
CP – Cellulose Proprionate
34
CPVC – Chlorinated Polyvinyl Chloride
36
ECTFE2.572.59
ETFE – Ethylene Tetrafluoroethylene
2.62.6
EVA – Ethylene Vinyl Acetate
2.53
EVOH – Ethylene Vinyl Alcohol
4.85.6
FEP – Fluorinated Ethylene Propylene
2.12.1
HDPE – High Density Polyethylene
2.32.3
HIPS – High Impact Polystyrene
2.44.8
HIPS Flame Retardant V0
23
LCP – Liquid Crystal Polymer
3.33.3
LCP Glass Fiber-reinforced
34
LCP Mineral-filled
35.9
LDPE – Low Density Polyethylene
2.32.3
LLDPE – Linear Low Density Polyethylene
2.32.3
MABS – Transparent Acrylonitrile Butadiene Styrene
2.83
PA 11 – (Polyamide 11) 30% Glass fiber reinforced
4.84.8
PA 11, Conductive
39
PA 11, Flexible39
PA 11, Rigid39
PA 12 (Polyamide 12), Conductive
39
PA 12, Fiber-reinforced
39
PA 12, Flexible39
PA 12, Glass Filled
39
PA 12, Rigid39
PA 46 – Polyamide 46
3.43.8
PA 46, 30% Glass Fiber
44.6
PA 6 – Polyamide 6
45
PA 6-10 – Polyamide 6-10
34
PA 66 – Polyamide 6-6
45
PA 66, 30% Glass Fiber
3.55.6
PA 66, 30% Mineral filled
45
PA 66, Impact Modified, 15-30% Glass Fiber
3.44.2
PA 66, Impact Modified
2.95
PAI – Polyamide-Imide
3.97.3
PAI, 30% Glass Fiber
4.26.5
PAR – Polyarylate
3.33.3
PARA (Polyarylamide), 30-60% glass fiber
3.94.5
PBT – Polybutylene Terephthalate
2.94
PBT, 30% Glass Fiber
34
PC (Polycarbonate) 20-40% Glass Fiber
33.5
PC (Polycarbonate) 20-40% Glass Fiber Flame Retardant
33.8
PC – Polycarbonate, high heat
2.83.8
PC/PBT Blend – Polycarbonate/Polybutylene Terephthalate Blend
2.953.14
PC/PBT blend, Glass Filled
3.33.9
PCTFE – Polymonochlorotrifluoroethylene
23
PE – Polyethylene 30% Glass Fiber
2.72.8
PEEK – Polyetheretherketone
3.23.2
PEEK 30% Carbon Fiber-reinforced
3.23.4
PEEK 30% Glass Fiber-reinforced
3.34.2
PEI – Polyetherimide
3.13.2
PEI, 30% Glass Fiber-reinforced
34
PEI, Mineral Filled
34
PEKK (Polyetherketoneketone), Low Cristallinity Grade
3.33.3
PESU – Polyethersulfone
3.54.1
PESU 10-30% glass fiber
4.24.3
PET – Polyethylene Terephtalate
34
PET, 30% Glass Fiber-reinforced
34
PETG – Polyethylene Terephtalate Glycol
34
PFA – Perfluoroalkoxy
2.12.1
PI – Polyimide3.13.55
PMMA – Polymethylmethacrylate/Acrylic
25
PMMA (Acrylic) High Heat
3.24
PMMA (Acrylic) Impact Modified
2.93.7
PMP – Polymethylpentene
2.13.6
PMP 30% Glass Fiber-reinforced
2.42.4
PMP Mineral Filled
2.32.3
POM – Polyoxymethylene (Acetal)
3.34.7
POM (Acetal) Impact Modified
44.3
POM (Acetal) Low Friction
34
PP – Polypropylene 10-20% Glass Fiber
2.62.6
PP, 10-40% Mineral Filled
2.32.3
PP, 10-40% Talc Filled
2.32.3
PP, 30-40% Glass Fiber-reinforced
2.62.6
PP (Polypropylene) Copolymer
2.32.3
PP (Polypropylene) Homopolymer
2.32.3
PP, Impact Modified
2.32.3
PPA – Polyphthalamide
4.34.3
PPA, 30% Mineral-filled
44.2
PPA, 33% Glass Fiber-reinforced
4.44.6
PPA, 33% Glass Fiber-reinforced – High Flow
3.73.9
PPA, 45% Glass Fiber-reinforced
4.44.6
PPE – Polyphenylene Ether
2.72.7
PPE, 30% Glass Fiber-reinforced
2.92.9
PPE, Flame Retardant
2.72.7
PPS – Polyphenylene Sulfide
33.3
PPS, 20-30% Glass Fiber-reinforced
3.33.8
PPS, 40% Glass Fiber-reinforced
44
PPS, Glass fiber & Mineral-filled
55
PPSU – Polyphenylene Sulfone
3.43.5
PS (Polystyrene) 30% glass fiber
2.52.5
PS (Polystyrene) Crystal
2.42.7
PS, High Heat2.42.7
PSU – Polysulfone
33.2
PSU, 30% Glass finer-reinforced
3.63.7
PTFE – Polytetrafluoroethylene
2.12.1
PTFE, 25% Glass Fiber-reinforced
33
PVC, Plasticized35
PVC, Plasticized Filled
35
PVC Rigid34
PVDC – Polyvinylidene Chloride
36
PVDF – Polyvinylidene Fluoride
69
SAN – Styrene Acrylonitrile
2.53.4
SAN, 20% Glass Fiber-reinforced
3.23.8
SMA – Styrene Maleic Anhydride
2.82.8
SMA, 20% Glass Fiber-reinforced
3.33.3
SMMA – Styrene Methyl Methacrylate
3.23.2
SRP – Self-reinforced Polyphenylene
3.13.1
UHMWPE – Ultra High Molecular Weight Polyethylene
2.32.3


Fascinating Read – What is the Density of Plastics? | The Complete Guide

FAQs 

Get ready to dive headfirst into the electrifying world of the dielectric strength of polymers! We’ve compiled a list of sizzling FAQs to quench your thirst for knowledge. Come on, let’s take a look!

What is the formula of dielectric strength?

M1L2T−2Q−1.

What is the dielectric strength of Bakelite?

300-550 Kv/inch

Why is plastic an electrical insulator?

In layman’s language, they don’t possess free electrons moving around, a phenomenon also called delocalized electrons. That makes them bad conductors of electricity and heat, which gives them the property of great insulators.

How can polymers be made electrically conductive?

The two main methods used to make insulators electrically conductive – Chemical synthesis and electro (co) polymerization. Chemical synthesis means connecting the carbon-carbon bond of monomers by placing the simple monomers under various conditions, such as heating, light exposure pressing, and catalyst.

Suggested Read 

Final Thoughts 

Dielectric strength, a measure of a plastic’s ability to resist electrical breakdown, is critical for insulating materials. Plastics, given their diverse chemical structures, exhibit varying dielectric strengths. Temperature, molecular arrangement, and impurities can impact this property.

As observed, some plastics maintain a relatively stable dielectric strength across temperature ranges, while others might see significant reductions.

Choosing the right plastic based on its dielectric strength, tailored to specific environmental conditions, is crucial for ensuring the safety and efficiency of electronic and electrical systems. Thus, a comprehensive understanding of a plastic’s dielectric properties is essential for optimal application.

Have a wonderful day.

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