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High-Temp High-Electrical Insulation Plastics: PEEK/PI/PPS/PEI/PPSU

PEEK, PI, PPS, PEI, and PPSU are the most widely used high-temperature high-insulation plastics. Depending on the grade, they offer continuous service temperatures of 160–300°C, volume resistivity above 10¹⁶ Ω·cm(IEC 60093), superior dielectric strength, intrinsic flame retardancy, and excellent dimensional stability. To select the right material for harsh service conditions such as high temperature, high voltage, humidity, or pollution, engineers must evaluate not only dielectric strength and volume resistivity, but also CTI, RTI Elec, dielectric loss, and moisture absorption.

Performance Profiles at a Glance

PEEK — Heat resistance + high insulation + high strength & toughness
PI — Heat resistance + high insulation + extreme thermal ceiling
PEI — Heat resistance + high insulation + thin-wall dielectric strength
PPS — Heat resistance + high insulation + cost-effectiveness
PPSU — Heat resistance + high insulation + high toughness & sterilizability

PEEK Material

Good comprehensive performance
260℃ Long-term electrical heat resistance
high strength & Good toughness
Excellent fatigue resistance

PI Material

Excellent heat resistance
Keep insulation over 300°C
Excellent mechanical strength

PEI Material

The thin-wall voltage leader
high dielectric strength
amorphous
dimensionally stable

PPS Material

The cost-effective choice
high CTI
ultra-low water absorption
outstanding chemical resistance

PPSU Material

intrinsic V-0
high toughness
The safety-compliance specialist
withstands over 1,000 steam sterilization cycles

Comparison of Core Electrical and Heat Resistance Parameters

Performance	PEEK	PI	PPS	PEI	PPSU	Test standard
Long term using temperature	260°C	260–300°C	200–240°C	170°C	160–180°C	UL 746B
Dielectric strength (thick section, kV/mm)	19–20	16–22	17–22	30–33	17–20	ASTM D149
Volume resistivity (Ω·cm)	10^16	10^16	10^16	10^17	10^16	IEC 60093
CTI (IEC 60112)	~150V	Varies widely	175–250V	~150V	~175V
RTI Elec (UL 746B)	260°C	240–300°C	200–220°C	170°C	160–170°C	UL 746B
Dielectric constant (1 kHz)	3.2	3.0–3.5	3.0–3.2	3.15–3.7	3.0–3.4	IEC 60250
Dielectric loss (tan δ)	0.003–0.005	0.001–0.003	0.001–0.002	0.0013–0.0015	0.001–0.003	IEC 60250
Water absorption 24h,23°C (ISO 62)	0.04-0.07%	0.5–1.5%	0.02–0.04%	0.1–0.25%	0.37%	ISO 62
UL94 flammability	V-0 (intrinsic)	V-0 (intrinsic)	V-0 (intrinsic)	V-0 (intrinsic)	V-0 (intrinsic)	UL94
Relative cost index	Baseline	3–5×	~1/3	~1/2	~2/3

Please note that the data provided above is for reference purposes only. Parameters given as a range are influenced by material grade. To find precise values for a specific model, please consult the detail page or download the TDS

From the table above, these materials exhibit high dielectric strength and excellent heat resistance, allowing them to maintain insulation in high-temperature and high-voltage environments. In addition, they feature very low water absorption — and when reinforced with glass fiber, PEEK, PPS, and PEI achieve even lower water absorption — which enables them to retain reliable insulation performance in high-humidity conditions.

Why choose PEEK,PEI,PPSU,PPS as High electrical insulation Material

Because these five materials have been selected through comprehensive evaluation of service temperature limits, water absorption, dielectric strength, flame retardancy, and chemical resistance. As a result, they can maintain reliable insulation performance even in harsh operating environments. In contrast, ordinary materials soften rapidly due to their low heat resistance, materials with high water absorption become unreliable in humid conditions, and those with low dielectric strength are prone to electrical breakdown.

High-Voltage Insulation Failure of Ordinary Engineering Plastics vs. the Stability of PEEK/PEI/PPS/PPSU

Material	Long-Term Temperature Limit	Failure Mode	PEEK/PEI/PPS/PPSU/PI
PP	90–110°C	Oxidative embrittlement and deformation after overheating cracking and breakdown under high voltage	PEEK:260°C PI:260–300°C PPS:200–240°C PPSU:160–180°C Chemical structure is stable and has low toxicity.
POM	90–110°C	Decomposes at high temperatures releasing formaldehyde which turns into formic acid in the presence of moisture corroding metal contacts and accelerating insulation failure
PVC	60–80°C (lower for flexible grades)	Plasticizer migration and HCl release hardens and cracks with a drop in insulation resistance
ABS	80–100°C	Thermal deformation brings it into contact with live parts surface tends to carbonize
PA66	130–150°C	Prolonged overheating causes thermo-oxidative aging darkening a sharp drop in mechanical strength surface cracking

Good Insulation stability under wet conditions

Material	Water Absorption (24h)	Wet-State Insulation Performance	Conclusion in High-Humidity Environments
PPS	0.02–0.04%	Volume resistivity virtually unchanged; dielectric strength stable	No concerns in humid environments; preferred for precision insulation
PEEK	0.04–0.07%	Extremely hydrolysis-resistant; stable in 200°C steam over long periods; minimal electrical degradation	Best for high-temperature/high-humidity and steam sterilization applications
PEI	0.1–0.25%	Stable dielectric performance in wet state; minimal dimensional change	Reliable for precision parts in medium-high temperature humid conditions
PI	0.5–1.5%(Grade-dependent)	Dielectric strength remains >200 kV/mm (film) under high temperature and humidity; volume resistivity stable	Benchmark for extreme high-temperature/high-humidity insulation
PPSU	0.37%	No hydrolysis or embrittlement after water absorption; volume resistivity maintained >10¹⁵ Ω·cm; retains >95% performance after 1,000 cycles of 134°C steam	Water absorption is not low, but “absorption ≠ failure”
PA6/PA66	1.5–3.5%	Volume resistivity drops from 10¹⁴ to 10¹² Ω·cm; dielectric strength decreases by 30–40%; prone to tracking	Insulation collapses in high-humidity environments
PC	0.1–0.2%	Surface water film lowers flashover voltage; dielectric strength decreases under damp heat; trace moisture during processing causes hydrolysis embrittlement	Usable in dry environments; limited under damp heat
POM	0.1–0.5%	Moisture combined with high temperature releases formaldehyde, causing surface corrosion and insulation degradation; extremely poor arc resistance	Use with caution in electrical applications
PET/PBT	0.1–0.2%	Basically stable in wet state, but temperature limits restrict high-voltage applications	Suitable for medium/low voltage in dry or mildly humid heat

High strength insulation Glass fiber filled grade:PEEK,PEI,PPS

PEEK,PPS and PEI material has excellent mechanical strength.They can also reinnforced by glass fiber to reach higher strength and higher UDT.

Glass fiber is also an insulation material,so after reinforced by glass fiber,PEEK ,PPS and PEI material can still keep highly insulation.

PPS virgin & PPS GF30 & PPS GF40

Performance	Unfilled PPS	PPS GF30	PPS GF40	Test Standard
Tensile Strength (23℃)	90 MPa	170 MPa	195MPa	ISO 527
Flexural Strength (23℃)	138 MPa	260 MPa	285MPa	ISO 178
Flexural Modulus (23℃)	3.6 GPa	11 GPa	14.7GPa	ISO 178

PPS material usually filled with 30% and 40% Glass fiber

PEEK virgin & GF30 grade

Performance	Unfilled PEEK	PEEK GF30	Test Standard
Tensile Strength (23℃)	100MPa	175MPa	ISO 527
Flexural Strength (23℃)	165MPa	265MPa	ISO 178
Flexural Modulus (23℃)	4.1GPa	11.3GPa	ISO 178

PEI virgin & PEI GF30 grade

Performance	Unfilled PEI	PEI GF30	Test Standard
Tensile Strength (23℃)	110MPa	159MPa	ASTM D638
Flexural Strength (23℃)	165MPa	228MPa	ASTM D790
Flexural Modulus (23℃)	3.5Gpa	8.9GPa	ASTM D790