What are the heat and voltage resistance of phenolic cotton cloth board?

Time: 09-23 2025 Auther: Xujue Electrical

Phenolic cotton cloth laminated sheet (also known as Bakelite cotton cloth board) is a classic electrical insulation ...

Phenolic cotton cloth laminated sheet (also known as Bakelite cotton cloth board) is a classic electrical insulation material with stable temperature and voltage resistance, suitable for various motors, electrical devices, and mechanical parts. Detailed performance is as follows:

phenolic cotton cloth sheet

Temperature Resistance

Heat Deflection Temperature (HDT): typically 130℃–150℃.

Continuous Operating Temperature: generally around 120℃, short-term can withstand 150℃.

High Temperature Class: considered Class B insulation material (according to IEC standards), suitable for medium-high temperature electrical environments.

Characteristics: Good thermal stability, resistant to delamination or cracking at high temperatures; commonly used for motor slot wedges, insulating supports, etc.

Voltage Resistance

Dielectric Strength: approximately 15–25 kV/mm (depends on thickness and manufacturing process).

Volume Resistivity: about 10¹²–10¹³ Ω·cm, offering excellent insulation.

Impulse Voltage Resistance: can withstand several kilovolts of pulse voltage, suitable for motors, transformers, and switches in high-voltage environments.

Characteristics: The insulation performance is stable; it does not break down or leak electricity during long-term operation.

Summary of Key Properties

Property	Value / Range	Notes
Heat Deflection Temperature	130℃–150℃	Suitable for medium-high temperature insulation applications
Continuous Operating Temperature	120℃	Meets Class B insulation standard
Dielectric Strength	15–25 kV/mm	Reliable in high-voltage environments
Volume Resistivity	10¹²–10¹³ Ω·cm	Excellent long-term insulation performance
Impulse Voltage Resistance	Several kV	Can withstand short-term high-voltage spikes

Typical Applications

Motor slot wedges and end-cap insulation

Transformer insulation sheets

Switchgear or high-voltage equipment insulating supports

Mechanical parts requiring electrical insulation

phenolic cotton sheet machined parts

Electrical Insulation Laminated Sheet Performance Comparison

Material	Heat Deflection Temperature (HDT)	Continuous Operating Temperature	Dielectric Strength	Volume Resistivity	Insulation Class	Features / Typical Applications
Phenolic Cotton Cloth Board	130℃–150℃	120℃	15–25 kV/mm	10¹²–10¹³ Ω·cm	Class B	Motor slot wedges, transformer insulation sheets, switchgear insulating supports
FR‑4 Epoxy Glass Fabric Laminate	130℃–170℃	130℃	20–30 kV/mm	10¹²–10¹³ Ω·cm	Class B/C	PCB substrates, high-voltage insulation sheets, electronic component supports
Phenolic Paper Board	105℃–130℃	105℃	10–20 kV/mm	10¹¹–10¹² Ω·cm	Class A/B	Motor end caps, low-voltage switch insulation, general mechanical insulation

Key Takeaways

Temperature resistance: FR‑4 > Phenolic Cotton Cloth Board > Phenolic Paper Board

Voltage resistance: FR‑4 and Phenolic Cotton Cloth Board are similar; Phenolic Paper Board is slightly lower

Application differences:

FR‑4: high-temperature, high-voltage electronic environments

Phenolic Cotton Cloth Board: motors and electrical equipment mechanical insulation parts

Phenolic Paper Board: low-voltage or general mechanical insulation

Leave us a message to get quotation and sample!

If you are interested in our products,, please send us a message and we will contact you as soon as we receive it. Email: info@ztaero.com whatsApp: +8616650273778