Dielectric strength describes how much electric field an insulating material can withstand before electrical breakdown, normally expressed in kilovolts per millimeter (kV/mm). Common FDM filaments such as PLA, PETG, ABS, ASA, PC/ABS, PA12, and some flexible polymers can behave as electrical insulators, but there is no universal dielectric-strength value for a polymer family. Printed-part values depend on the exact formulation, specimen thickness and geometry, print quality, internal voids, moisture, temperature, electrode arrangement, and test method. A published value therefore describes the tested specimens and conditions rather than providing a safe voltage rating for every part printed from that filament.
| Material | Average Breakdown Strength | Relative Result Within This Test |
|---|---|---|
| ABS | 30.28 kV/mm | Highest measured value |
| PC/ABS | 30.14 kV/mm | Very close to ABS |
| PETG | 27.55 kV/mm | Between ABS/PC-ABS and PLA |
| PLA | 23.45 kV/mm | Below PETG in this specimen set |
| ASA | 20.35 kV/mm | Lowest measured value in the group |
These values came from FDM-printed specimens evaluated under controlled conditions using IEC 60243-based dielectric breakdown testing. They are useful for comparing the materials within that experiment, not as universal ratings for every PLA, PETG, ABS, ASA, or PC/ABS filament. [a]
What Dielectric Strength Measures
An electrical insulator does not conduct freely under ordinary conditions, but a sufficiently strong electric field can eventually force a conductive path through or around it. The electric field at which this failure occurs is used to characterize dielectric strength.
The basic relationship is:
E = V / d
E = electric field strength, V = applied voltage, and d = specimen thickness.
If a 1 mm specimen breaks down at 20 kV under a particular test arrangement, the calculated breakdown strength is 20 kV/mm. If a 2 mm specimen breaks down at 30 kV, its calculated value is 15 kV/mm. This normalization makes comparison easier, but it does not guarantee that breakdown voltage scales linearly with wall thickness.
ASTM D149-25 covers dielectric breakdown voltage and dielectric strength of solid electrical insulating materials at commercial power frequencies. The standard allows testing under defined temperatures and surrounding media and emphasizes control of the test conditions used to generate the result. [b]
Dielectric Strength Is Not Electrical Resistance
Several electrical properties appear together on polymer data sheets, but they answer different questions. A material can have very high electrical resistance and still have a breakdown strength that differs markedly from another high-resistance polymer.
| Property | What It Describes | Typical Expression |
|---|---|---|
| Dielectric strength | Electric field at which insulation breaks down | kV/mm |
| Breakdown voltage | Voltage at which a particular specimen fails | V or kV |
| Volume resistivity | Resistance to current flowing through the bulk material | Ω·m or Ω·cm |
| Surface resistivity | Resistance to current traveling along a surface | Ω or Ω/square, depending on reporting convention |
| Relative permittivity | How strongly the dielectric polarizes in an electric field | Dimensionless |
| Dissipation factor | Electrical energy loss in an alternating field | Dimensionless |
This distinction also separates ordinary insulating filament from ESD or conductive formulations. A polymer designed to dissipate electrostatic charge has a different electrical objective from a high-resistance insulating polymer. Carbon black, carbon fibers, conductive nanotubes, metallic particles, and other additives can alter resistance, permittivity, losses, and breakdown behavior.
High resistivity does not automatically mean high dielectric strength. Resistivity describes current flow before breakdown; dielectric strength describes the electrical field associated with insulation failure.
Published FDM Values Vary More Than a Single Material Number Suggests
The 2026 comparison shown above found average values from 20.35 to 30.28 kV/mm for its ABS, PC/ABS, PETG, PLA, and ASA specimens. [a] A separate study of 24 FFF materials produced a much wider spread and also found different results among multiple products belonging to the same polymer family. [c]
| Material Group | Reported Dielectric Strength | Interpretation |
|---|---|---|
| PLA, product 1 | 13.38 kV/mm | Highest of three PLA products in that study |
| PLA, product 2 | 7.70 kV/mm | Different commercial PLA formulation |
| PLA, product 3 | 9.61 kV/mm | Different commercial PLA formulation |
| PETG, product 1 | 13.49 kV/mm | First PETG product tested |
| PETG, product 2 | 15.18 kV/mm | Second PETG product tested |
| PA12 | 32.61 kV/mm | Single PA12 product in the study |
| TPU 98A | 23.13 kV/mm | Single TPU grade in the study |
| PP | 17.68 kV/mm | Single PP product in the study |
These results should not be merged with the 2026 table to create an average for each polymer. The specimens, filament products, and experimental conditions are not identical. [c]
The three PLA products in the 24-filament study ranged from 7.70 to 13.38 kV/mm, while the PLA specimens in the 2026 study averaged 23.45 kV/mm. That difference is exactly why a statement such as “PLA has a dielectric strength of X kV/mm” is too broad without a product, specimen, and test context.
Why FDM Parts Differ from Molded Polymer Data
A molded electrical-insulation specimen can approach a continuous polymer body. FDM produces a layered structure from individual extrusion roads. Even a visually solid print may contain inter-bead gaps, interlayer interfaces, seam regions, local under-extrusion, or small pores. These features can alter local electric-field distribution and create paths that are absent from a homogeneous bulk specimen.
A 2026 study of oil-immersed PLA specifically examined process-induced voids and interlayer interfaces as electrical-field concentration sites. The researchers varied extrusion temperature and nozzle diameter and found that processing conditions affected AC breakdown performance. [d]
Resin data, molded-specimen data, and FDM-part data are different evidence levels. A dielectric value measured on an injection-molded plaque should not be presented as a measured value for a printed wall unless the manufacturer explicitly tested the printed configuration.
Specimen Geometry and Thickness Can Change the Result
A 2024 study demonstrates how strongly the measured result can change when the specimen configuration changes. The researchers printed cylindrical specimens 50 mm in diameter and 1.2 mm thick, as well as square specimens 50 mm wide and 2.4 mm thick. Both configurations used a 0.2 mm layer height and 100% nominal fill. [e]
| Material | Cylindrical Specimen | Square Specimen |
|---|---|---|
| PLA | 23.45 kV/mm | 15.75 kV/mm |
| ABS | 30.28 kV/mm | 18.73 kV/mm |
| ASA | 20.35 kV/mm | 13.06 kV/mm |
| PETG | 27.55 kV/mm | 14.94 kV/mm |
| PC/ABS | 30.14 kV/mm | 8.29 kV/mm |
The configurations differed in both shape and thickness, so this table should not be interpreted as a clean test of shape alone. It shows why specimen configuration must accompany any dielectric-strength number. [e]
PC/ABS is an especially clear example. A reader looking only at the cylindrical result would see 30.14 kV/mm; the square configuration in the same investigation produced an average of 8.29 kV/mm. A material name and a kV/mm number are therefore not enough information for engineering use.
Layer Height, Extrusion Quality, and Internal Voids
Printing parameters can affect electrical behavior because they change how well neighboring roads and layers fuse. However, simple rules such as “lower layer height always gives higher dielectric strength” are not supported across all materials.
A Czech Technical University study printed PLA, ABS, and PET-G samples at layer heights of 50, 100, 150, and 200 µm and measured permittivity, dissipation factor, and dielectric strength. Material type remained a major influence, while the relationship between layer height and dielectric strength differed by polymer and print quality. PLA showed a decline in dielectric strength as layer height increased in that experiment, ABS did not produce a clear resolution-dependent pattern, and PET-G behaved differently because print quality changed with the selected processing conditions. [f]
For an insulating FDM part, the processing goal is therefore not merely the smallest possible layer height. More useful objectives are stable extrusion, good inter-road contact, repeatable layer bonding, minimal porosity, and avoidance of under-extruded regions.
Why 100% Infill Is Not the Same as a Void-Free Solid
A slicer setting of 100% infill tells the toolpath generator to fill the intended interior. It does not certify microscopic density. Small gaps can still form between extrusion roads, around perimeter-to-infill interfaces, at seams, or where flow and temperature are poorly controlled.
For electrical insulation, wall structure may matter more than a headline infill percentage. Multiple well-fused perimeters can create a different dielectric path from a thin outer shell surrounding a large infill region, even if the overall nominal fill percentage looks favorable.
Print Orientation and Electric-Field Direction
FDM parts are direction-dependent structures. An electric field passing across many layer interfaces encounters a different microstructure from a field running largely within deposited roads. The exact effect depends on porosity, fusion, material, field configuration, and the orientation of defects.
This makes a generic XY or Z rating unreliable unless the test report defines how the sample was printed and how the electric field was applied. A manufacturer value that omits specimen orientation should not be converted into a directional printed-part specification.
Moisture Matters Before and After Printing
Moisture can affect electrical-insulation performance through more than one route. Moist filament may produce bubbles, poor road formation, or internal pores during extrusion. A finished hygroscopic polymer can also absorb moisture during service, changing its electrical behavior compared with a dry, freshly conditioned test specimen.
The 2026 PLA high-voltage study treated moisture uptake as a relevant variable and printed specimens shortly before testing to reduce moisture absorption. It also warned that bulk-polymer electrical properties may differ from those of FDM parts because of the printed microstructure. [d]
Drying can be an electrical-quality issue as well as a print-quality issue. This is particularly relevant for moisture-sensitive filament families and for testing intended to compare small differences between materials or print settings.
PA and PA-based filaments deserve extra care because polyamides can absorb appreciable moisture. PLA, PETG, TPU, and other formulations can also require controlled storage and conditioning. The required drying procedure is product-specific; temperature and time should come from the filament manufacturer rather than from a generic polymer-family rule.
Temperature Can Change Whether a Material Is Suitable
A good room-temperature breakdown result does not automatically make a filament suitable for a warm enclosure or power-electronics environment. Electrical performance must be considered alongside heat deflection, glass-transition behavior, creep, dimensional stability, and long-term service temperature.
This is one reason PLA cannot be ranked solely from its dielectric-strength value. PLA can provide useful insulating behavior, but an enclosure operating near its thermal limits may deform or lose dimensional accuracy before electrical breakdown becomes the primary material limitation.
ABS, PC blends, and other engineering polymers may offer a wider thermal operating margin, but they introduce their own processing requirements. Material selection therefore cannot be reduced to the highest kV/mm figure in a laboratory table.
How Common Filament Families Compare
PLA
Standard unfilled PLA is normally electrically insulating, but published FDM measurements vary widely. The 2026 comparison reported 23.45 kV/mm for its PLA specimens, while three PLA products in the 2021 multi-material study measured 7.70, 9.61, and 13.38 kV/mm. [a] [c]
PLA’s easy printing makes it practical for experimental fixtures, covers, brackets, and low-demand insulating structures where the actual electrical requirements are modest and independently evaluated. Its lower thermal margin compared with many engineering thermoplastics can become the limiting property in warm equipment.
PETG
PETG produced 27.55 kV/mm in the 2026 comparison, higher than PLA within that experiment. Two PETG products in the 2021 study measured 13.49 and 15.18 kV/mm, again illustrating that cross-study numbers should not be treated as universal material constants. [a] [c]
PETG can offer a useful combination of electrical insulation, layer adhesion, toughness, and desktop printability. Moisture control and clean extrusion still matter because a poor print can create voids that are absent from the polymer data sheet.
ABS
ABS recorded the highest dielectric strength in the 2026 five-material comparison at 30.28 kV/mm. [a] Earlier printing-resolution research also found ABS capable of strong dielectric performance, although unstable surface quality in some samples made the relationship with layer height less clear. [f]
That does not make every ABS filament the highest-performing electrical insulator. Warping, interlayer defects, formulation changes, pigments, enclosure temperature, and specimen design can all alter the finished part.
ASA
ASA averaged 20.35 kV/mm in the 2026 comparison, the lowest value among the five materials tested there. [a] ASA is often chosen for weathering and outdoor performance, but UV or environmental durability should not be interpreted as evidence of higher dielectric strength.
PC and PC/ABS
PC/ABS was close to ABS in the 2026 dataset at 30.14 kV/mm. The 2021 multi-material study measured 20.67 kV/mm for its PC/ABS product and 14.78 kV/mm for its PC product. [c] These materials can be attractive where higher temperature capability is also required, but printing usually demands more heat and tighter process control than PLA or PETG.
PA12, TPU, TPE, and PP
The broader 2021 study shows why common desktop materials should not be the only reference point. Its PA12 product reached 32.61 kV/mm, TPU 98A measured 23.13 kV/mm, PP measured 17.68 kV/mm, and the tested TPE grades ranged from 22.30 to 41.52 kV/mm. [c]
Those values describe specific tested products. Flexible polymers can differ in chemistry, hardness, additives, and electrical losses, while PA grades can be especially sensitive to moisture conditioning. A generic “TPU” or “nylon” dielectric-strength number is therefore a poor substitute for product-specific test data.
Fillers, Pigments, and Special Formulations Can Change the Electrical Behavior
Filament names describe a base polymer but rarely describe the entire formulation. Colorants, impact modifiers, flame-retardant packages, mineral fillers, glass fibers, carbon fibers, carbon black, conductive particles, plasticizers, and recycled content can change electrical properties.
The 24-material FFF study included standard polymers alongside carbon-filled and ESD-related formulations and found a broad range of dielectric and resistivity behavior across the tested products. [c] This is why a dielectric-strength value for ordinary PLA should not automatically be assigned to PLA-CF, flame-retardant PLA, glow-in-the-dark PLA, ESD PLA, or another modified grade.
The same rule applies to color. A black filament is not automatically conductive, and a natural filament is not automatically a better insulator. The pigment chemistry and concentration matter. If electrical insulation is part of the design requirement, the exact product’s technical data are more useful than color-based assumptions.
Estimating Breakdown Voltage from Wall Thickness
Dielectric strength can be converted into an idealized breakdown-voltage estimate by multiplying the field strength by specimen thickness:
Estimated breakdown voltage = dielectric strength × thickness
Example: 20 kV/mm × 2 mm = 40 kV.
The arithmetic is useful for understanding the unit, but the result is not a safe working-voltage rating. Real breakdown strength may vary with thickness, electrode geometry, defects, moisture, temperature, frequency, surrounding medium, surface condition, and statistical variation between specimens.
| Wall Thickness | 10 kV/mm | 20 kV/mm | 30 kV/mm |
|---|---|---|---|
| 0.5 mm | 5 kV | 10 kV | 15 kV |
| 1 mm | 10 kV | 20 kV | 30 kV |
| 2 mm | 20 kV | 40 kV | 60 kV |
| 3 mm | 30 kV | 60 kV | 90 kV |
The table is only the mathematical product of field strength and thickness. It does not include a safety factor and does not account for creepage, clearance, flashover, defects, aging, contamination, or certification requirements.
The Weakest Electrical Path May Not Pass Through the Wall
Dielectric-strength testing is commonly associated with puncture through a specimen, but an actual component can fail by a different path. ASTM D149-25 distinguishes through-thickness breakdown from flashover along an interface. [b]
- Through-thickness breakdown: the electrical path passes through the printed polymer wall.
- Surface flashover: discharge travels along the surface or along an interface beside the solid.
- Air-gap discharge: the electric field crosses an unintended air space instead of the intended solid insulation.
- Tracking: repeated surface electrical stress and contamination can create a progressively conductive path.
A thick printed wall therefore cannot compensate automatically for insufficient spacing around conductors, sharp field concentrations, contaminated surfaces, or an unsuitable enclosure layout.
Dielectric Strength Is Only One Requirement for an Electrical Enclosure
For a low-voltage experimental cover or fixture, dielectric behavior may be only one material-selection criterion. For mains-powered or higher-voltage equipment, additional insulation design requirements become separate issues.
- Clearance through air
- Creepage distance along insulating surfaces
- Resistance to surface tracking
- Temperature and thermal aging
- Flammability requirements
- Moisture and contamination
- Mechanical retention of live components
- Manufacturing repeatability
- Product-specific electrical safety standards
A published filament dielectric-strength value should not be used by itself to certify a printed isolation barrier. Mains isolation, medical electrical equipment, high-voltage power electronics, EV systems, transformers, and other safety-related applications require the applicable design rules and validation of the finished insulation system.
How Dielectric Strength Is Tested
A dielectric-strength test places a solid specimen between or adjacent to specified electrodes and raises the applied voltage under defined conditions until breakdown occurs. The recorded breakdown voltage is then related to specimen thickness when dielectric strength is reported in kV/mm.
IEC 60243-1:2013 specifies short-time electric-strength methods for solid insulating materials at power frequencies from 48 to 62 Hz and also includes methods dealing with breakdown along solid surfaces. The publication remains the current IEC 60243-1 edition, with a stability date listed as 2029. [g]
ASTM D149-25 is the active ASTM method for dielectric breakdown voltage and dielectric strength of solid electrical insulating materials at commercial power frequencies. Its scope normally uses 60 Hz unless otherwise specified and permits frequencies from 25 to 800 Hz. ASTM also states that this method is not intended to determine intrinsic dielectric strength or direct-voltage dielectric strength. [b]
AC, DC, and Impulse Results Are Not Interchangeable
A material tested with commercial-frequency AC voltage has not automatically been characterized for DC, lightning-like impulses, switching impulses, or prolonged electrical aging. Waveform, frequency, ramp rate, and exposure duration influence how insulation is stressed. A technical data sheet should therefore identify the applicable test method rather than reporting an isolated kV/mm figure.
What Breakdown Damage Can Look Like in a Printed Polymer
Electrical breakdown does not necessarily leave a clean, reversible puncture. It can locally melt polymer, leave a pinhole or crater, carbonize material, and establish a damaged path that has very different electrical properties from the original print.
The 2026 ABS, PLA, PETG, ASA, and PC/ABS study also analyzed post-breakdown surface damage. PLA showed the lowest measured surface-damage ratio in that experiment even though ABS produced the highest dielectric breakdown strength. [a] The material with the highest breakdown field is therefore not necessarily the material that shows the least visible damage after failure.
How to Read a Filament Technical Data Sheet for Electrical Use
A useful electrical specification contains more information than the polymer name and a dielectric-strength number. The closer the test conditions are to the intended printed part, the more informative the data become.
| Data-Sheet Detail | Why It Matters |
|---|---|
| Dielectric strength | Provides the measured electric-field value, commonly in kV/mm. |
| Breakdown voltage | Shows the actual failure voltage for the tested specimen. |
| Test method | Identifies whether ASTM D149, IEC 60243, or another procedure was used. |
| Specimen thickness | Breakdown behavior can vary with thickness. |
| Specimen manufacturing method | Separates FDM data from molded or otherwise manufactured material data. |
| Electrical waveform and frequency | Distinguishes AC, DC, impulse, and frequency-dependent measurements. |
| Conditioning | Temperature and humidity history can affect polymer behavior. |
| Test temperature | Prevents room-temperature data from being assumed valid at elevated temperature. |
| Surface and volume resistivity | Provides separate information about current conduction before breakdown. |
| Relative permittivity and loss | Useful where AC fields, capacitive behavior, or dielectric heating matter. |
Weak specification: “Excellent electrical insulator.”
More useful: “Dielectric strength: 22 kV/mm.”
Better documented: “22 kV/mm, stated test method, specimen thickness, conditioning, frequency, and manufacturing method.”
Selecting a Filament When Electrical Insulation Matters
No single filament family is the correct choice for every insulating part. Selection should combine product-specific electrical data with the temperatures, mechanical loads, moisture exposure, print process, and regulatory requirements of the application.
| Application Need | Material Direction | What Must Still Be Verified |
|---|---|---|
| Easy-printing experimental insulating component | PLA or PETG | Actual formulation, wall quality, temperature, and required electrical spacing |
| Higher-temperature enclosure or fixture | ABS, PC/ABS, PC, or another engineering polymer | Printed-part dielectric data and process quality |
| Outdoor housing | ASA may be considered for weather exposure | Electrical properties must be checked separately from weather resistance |
| Tough moisture-sensitive part | PA-based material where its other properties are needed | Conditioning, moisture uptake, and product-specific electrical data |
| Flexible insulating component | TPU or TPE grade | Exact formulation, resistivity, dielectric strength, losses, and temperature range |
| Electrostatic-dissipative fixture | Purpose-made ESD formulation | Specified resistance range; this is a different objective from maximizing insulation resistance |
For development work, the strongest evidence is a printed specimen made from the same filament formulation, using a documented print process, tested in a configuration relevant to the finished component. Generic polymer-family data are useful for screening materials, but they should sit lower in the evidence chain.
Frequently Asked Questions
Is PLA an electrical insulator?
Standard unfilled PLA normally behaves as an electrical insulator, but there is no universal dielectric-strength value for every PLA filament. Published FDM results vary with formulation, printing conditions, specimen geometry, thickness, and test method. Three commercial PLA products in one study ranged from 7.70 to 13.38 kV/mm, while another controlled study reported 23.45 kV/mm for its PLA specimens. [c] [a]
Does PETG have higher dielectric strength than PLA?
It can under particular test conditions. In the 2026 five-material comparison, PETG averaged 27.55 kV/mm and PLA averaged 23.45 kV/mm. Those values establish the ranking only for that tested material set and specimen configuration; they do not prove that every PETG filament has higher dielectric strength than every PLA filament. [a]
Does 100% infill maximize dielectric strength?
Not necessarily. A 100% slicer setting does not guarantee a pore-free solid. Inter-road gaps, seams, under-extrusion, imperfect fusion, nozzle temperature, and other processing variables can remain. Published research has shown that FDM processing conditions can alter dielectric breakdown behavior even when the base polymer is unchanged. [d]
Can dielectric strength be multiplied by wall thickness to find a safe voltage?
The multiplication gives an idealized breakdown-voltage estimate, not a safe operating voltage. Actual insulation design must account for specimen and part geometry, creepage, clearance, surface flashover, defects, moisture, temperature, contamination, aging, and the electrical-safety requirements that apply to the equipment.
Is carbon-fiber filament suitable as an electrical insulator?
It cannot be assumed from the base polymer. Carbon-containing formulations can have electrical properties that differ sharply from unfilled PLA, ABS, PA, or other polymers. Some carbon-filled products remain relatively resistive, while ESD and conductive formulations are intentionally designed to move charge. Product-specific resistivity and dielectric data are needed.
Is dielectric strength the same as dielectric constant?
No. Dielectric strength describes electrical breakdown under a strong field and is commonly reported in kV/mm. Relative permittivity, often called dielectric constant, describes polarization in an electric field and is dimensionless. A material can have a low relative permittivity without having the highest breakdown strength.
Can a filament manufacturer’s resin dielectric value be used for a printed enclosure?
It can provide material-level context, but it should not be presented as a measured property of the printed enclosure unless the testing actually used a comparable printed specimen. FDM introduces layer interfaces, voids, orientation, and process variation that are absent from many molded-resin test plaques.
Sources
- Polymers — Integrated Evaluation of Electrical Breakdown Strength and Mechanical Properties of 3D-Printed Polymers, Supplemented by ImageJ-Based Surface Damage Analysis — Supports the 2026 FDM breakdown-strength comparison for ABS, PLA, PETG, ASA, and PC/ABS and the post-breakdown surface-damage findings. (Peer-reviewed journal article.)
- ASTM International — ASTM D149-25: Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at Commercial Power Frequencies — Supports definitions, test scope, commercial-frequency conditions, puncture and flashover distinctions, and limitations of the method. (Official standards organization.)
- Polymers — FFF 3D Printing in Electronic Applications: Dielectric and Thermal Properties of Selected Polymers — Supports product-specific dielectric-strength variation across 24 FFF materials, including PLA, PETG, PA12, TPU, TPE, PP, PC, and PC/ABS. (Peer-reviewed journal article.)
- Energies — Influence of FDM Processing Parameters on the AC Breakdown Strength of Oil-Immersed PLA Insulation — Supports the effects of extrusion conditions, voids, interlayer interfaces, and moisture considerations on printed PLA insulation. (Peer-reviewed 2026 journal article.)
- Applied Sciences — Assessment of Dielectric Strength for 3D Printed Solid Materials in Terms of Insulation Coordination — Supports the specimen-configuration comparison and measured breakdown-strength differences for PLA, ABS, ASA, PETG, and PC/ABS. (Peer-reviewed journal article.)
- Czech Technical University in Prague — Evaluation of Dielectric Properties of 3D Printed Objects Based on Printing Resolution — Supports the layer-height investigation for PLA, ABS, and PET-G and the material-dependent effect of printing resolution. (University research repository for an IOP conference paper.)
- International Electrotechnical Commission — IEC 60243-1:2013, Electric Strength of Insulating Materials: Tests at Power Frequencies — Supports the IEC test scope, 48–62 Hz frequency range, and current publication status. (Official international standards organization.)