Polymer Dielectric Constant Table: Understanding Electrical Insulation in Plastics
What Is the Dielectric Constant of a Polymer?
The dielectric constant — also called relative permittivity (ε_r) — is a fundamental electrical property of polymers that quantifies their ability to store electrical energy when placed in an electric field. It is defined as the ratio of the capacitance of a capacitor with the polymer as its dielectric to the capacitance of the same capacitor with a vacuum between its plates. A polymer with a dielectric constant of 3.0 stores three times the electrical charge of vacuum under identical conditions.
For engineers designing electrical insulation systems, capacitors, PCB substrates, and high-frequency electronic components, the dielectric constant is one of the most important material selection parameters — governing signal speed, capacitive coupling, energy storage density, and insulation performance across the electronics, telecommunications, automotive, and aerospace industries.
Factors That Influence Polymer Dielectric Constant
Chemical Structure and Polarity
The most fundamental determinant of a polymer’s dielectric constant is whether its molecular structure contains permanent dipoles:
- Non-polar polymers (PTFE, PE, PP, PS) — symmetrical molecules with no permanent dipoles — have low dielectric constants (2.0–2.6). Only electronic polarization contributes, making them excellent high-frequency insulators.
- Polar polymers (PVC, nylon, polycarbonate, PMMA) — contain electronegative groups (–Cl, –C=O, –NH, –OH) that create permanent dipoles — have higher dielectric constants (3.0–7.5+) because orientational polarization adds to the electronic contribution.n
Crystallinity
Crystalline regions pack polymer chains more tightly than amorphous regions — reducing chain mobility and dipole alignment freedom. Higher crystallinity generally results in a lower dielectric constant than in the amorphous regions of the same polymer. This is why HDPE (higher crystallinity) has a slightly lower dielectric constant than LDPE.
Temperature
For polar polymers, increasing temperature increases chain mobility, enhancing dipole alignment and raising the dielectric constant. Non-polar polymers show minimal temperature sensitivity because electronic polarization is essentially temperature-independent.
Frequency
At higher frequencies, slower polarization mechanisms (orientational and ionic) cannot follow the alternating field, and their contribution to the dielectric constant drops out. All polymer dielectric constants decrease with increasing frequency, though non-polar polymers show minimal change since only fast electronic polarization contributes.
Moisture Absorption
Water has an exceptionally high dielectric constant (~80). Even small amounts of absorbed moisture dramatically increase the dielectric constant of hygroscopic polymers (nylons, cellulosics, polyimides). Dry conditions during testing and application are critical for moisture-sensitive polymers.
Polymer Dielectric Constant Reference Table
Polymer | Dielectric Constant (1 kHz, 23°C) | Notes |
PTFE (Teflon) | 2.0–2.1 | Lowest dielectric constant polymer |
Polyethylene (PE) | 2.2–2.4 | Non-polar; frequency-insensitive |
Polypropylene (PP) | 2.2–2.6 | Excellent low-loss insulator |
Polystyrene (PS) | 2.4–2.7 | Low loss; RF applications |
Silicone (PDMS) | 2.6–3.0 | Flexible; broad temperature range |
Polycarbonate (PC) | 2.9–3.2 | Moderate; engineering grade |
Polyimide (PI) | 3.0–3.5 | Dry; absorbs moisture |
Epoxy (standard) | 3.5–5.0 | Varies with cure and filler |
PVC (rigid) | 3.0–4.0 | Plasticizer-dependent |
PMMA (acrylic) | 2.6–3.7 | Moisture-sensitive |
Nylon 6.6 (dry) | 3.4–3.9 | Increases significantly when wet |
Polyester (PET) | 3.0–3.5 | Used in capacitor films |
PVDF | 8.0–12.0 | High dielectric; piezoelectric applications |
Test Methods for Polymer Dielectric Constant
ASTM D150 is the primary standard for measuring AC loss characteristics and permittivity (dielectric constant) of solid electrical insulating materials. Specimens are placed between two electrode plates and measured at a defined frequency and temperature using precision LCR meters or impedance analyzers. Measurements are typically performed from 10 Hz to 10 MHz and from room temperature to 200°C, depending on the application requirement.
Applications Requiring Low Dielectric Constant Materials
- High-frequency PCB substrates: Signal propagation speed increases with lower dielectric constant; PTFE-based substrates (Rogers, Teflon laminates) minimize signal delay at GHz frequencies
- 5G antenna radomes: Low-loss, low-dielectric-constant polymers preserve signal integrity through antenna enclosures
- Coaxial cable dielectrics: PTFE and foam PE minimize signal attenuation in precision RF cables
- High-voltage insulation: Polymers with stable,e low dielectric constants prevent capacitive coupling and corona discharge
Conclusion
The polymer dielectric constant table is an essential reference for electrical engineers, material scientists, and product designers selecting insulating polymers for electrical and electronic applications. Understanding how frequency, temperature, moisture, and molecular structure influence dielectric constant — and knowing which ASTM test standard generates the data — ensures that material selection decisions are grounded in comparable, reproducible data rather than ambiguous datasheet values.
Why Choose Infinita Lab for Polymer Dielectric Testing?
Infinita Lab is a trusted USA-based testing laboratory offering polymer dielectric constant and dissipation factor testing per ASTM D150 across an extensive network of accredited facilities. Our advanced equipment and expert professionals deliver highly accurate and prompt test results, helping businesses achieve quality compliance and product reliability.
Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you. Request a Quote
Frequently Asked Questions (FAQs)
Why is PTFE the preferred polymer for high-frequency electrical insulation? PTFE has the lowest dielectric constant (2.0–2.1) and lowest dielectric loss of all polymers due to its perfectly symmetrical non-polar molecular structure. At microwave and RF frequencies, it maintains stable properties with minimal signal attenuation — making it irreplaceable in precision RF connectors and antenna substrates.
How does moisture affect the dielectric constant of nylon? Nylon absorbs 2–10% moisture, and water's extremely high dielectric constant (~80) dramatically increases nylon's measured dielectric constant. Dry nylon 6.6 has ε_r ~3.4; equilibrated at 50% RH it rises to ~4.0–5.0. ASTM D150 testing must specify conditioning to enable comparable results.
What is the relationship between dielectric constant and signal propagation speed in PCB laminates? Signal propagation velocity in a PCB trace = c/√ε_r, where c is the speed of light. Lower dielectric constant directly increases signal speed — critical for high-frequency digital and RF designs. PTFE laminates (ε_r ~2.2) propagate signals approximately 30% faster than standard FR4 (ε_r ~4.5).
What is the dissipation factor and how does it relate to dielectric constant? Dissipation factor (tan δ) is the ratio of energy lost per cycle to energy stored — measuring the material's inefficiency as a capacitor. Materials with low tan δ waste less energy as heat. Both dielectric constant and dissipation factor are measured per ASTM D150 and reported together for complete electrical characterization.
Can dielectric constant be measured at elevated temperatures? Yes. ASTM D150 measurements can be performed in temperature-controlled test fixtures from cryogenic temperatures to above 200°C. Temperature profiling of dielectric properties is essential for materials used in automotive electronics, power inverters, and high-temperature applications where ambient-temperature data underestimates operational behavior.
