Red Prepreg DMD and White DMD Materials: Thickness, Density, and Grade Guide

DMD insulation materials are commonly used for interlayer, slot-to-slot, and phase-to-phase insulation in electrical equipment such as motors and transformers due to their excellent electrical properties and mechanical strength. Depending on the application requirements, red prepreg DMD and white DMD have become common choices. This article analyzes these two materials from three aspects: thickness specifications, density differences, and insulation grades, providing selection references for engineers and purchasing personnel.

What is DMD Insulation Material?

DMD is a three-layer insulation material composed of a polyester film and two layers of non-woven cloth. It possesses electrical insulation and mechanical flexibility, and is mainly used in the following applications:

Interlayer insulation of transformer windings

Slot insulation of motors

Phase-to-phase insulation of electrical equipment

Differences between Red Prepreg DMD and White DMD

1. Red Prepreg DMD Material

Red prepreg DMD is a material made by pre-impregnating ordinary DMD with heat-resistant resin.

Main Features:

Red Appearance: Easy to identify

Uniform Resin Distribution and Good Heat Resistance

More Stable Structure After Hot Pressing

Suitable for Mid-to-High-End Transformers and Motors

2. White DMD Material

White DMD is standard DMD material that is unpre-impregnated or only lightly treated.

Main Features:

Lower Cost

Good Flexibility and Easy Processing

Suitable for General Insulation Applications

Mostly Used in Ordinary Motors and Low-Voltage Transformers

Red Prepreg DMD and White DMD Materials: Thickness, Density, and Grade

1. Thickness

Thickness affects the electrical strength, space occupied, and flexibility of insulation materials. Common units are millimeters (mm) or micrometers (μm).

Common Thickness Ranges:

♦ White DMD: 0.15mm, 0.20mm, 0.25mm, 0.30mm, etc.

♦ Red Prepreg DMD: 0.1mm, 0.12mm, 0.15mm, etc.

Red prepreg DMD may have a slightly higher actual thickness for the same nominal thickness due to the resin content.

Selection Recommendations:

♦ Low-voltage small motors: Generally, 0.15-0.20mm white DMD material is selected.

♦ Medium-high voltage motors: It is recommended to use 0.20-0.30mm or thicker material. If VPI technology is used, select red prepreg DMD of the corresponding thickness.

2. Relationship between Density and Material Properties

The density of DMD material is related to its structural compactness and mechanical strength.

White DMD has a lower density and better flexibility. Red prepreg DMD has a slightly higher density and a more compact structure. Higher-density DMD materials typically have the following characteristics:

Better voltage resistance

Stronger compressive and tear resistance

Better thermal aging stability

3. Insulation Class and Thermal Performance

DMD Type	Insulation Class	Maximum Continuous Operating Temperature
White DMD	Class B	130 °C
Red Prepreg DMD	Class F (typical)	155 °C

For equipment operating at higher temperatures or under significant load fluctuations, red prepreg DMD is recommended as the preferred choice.

How to Select the Right DMD Material for Your Application

1. Process Requirements

For VPI, molding, or roll-impregnation processes that require integral coil forming, choose red prepreg DMD.

For conventional wrapping or insertion insulation methods without overall impregnation, white DMD is suitable.

2. Electrical Requirements

Select the thickness and dielectric strength (kV/mm) of the insulation material based on the equipment’s operating voltage.

Thicker materials are recommended for high-voltage applications.

3. Operating Environment

The long-term operating temperature determines the required insulation class (e.g., Class B or Class F).

In humid environments, chemically corrosive conditions, or applications with high vibration, red prepreg DMD with curable sealing properties is recommended.

4. Mechanical Requirements

For areas with higher mechanical strength, abrasion resistance, or tensile requirements, select DMD materials with higher density and greater thickness.

Red prepreg DMD and white DMD each have distinct advantages in terms of structure, density, and insulation class. Selecting the appropriate thickness and thermal rating based on actual application requirements ensures electrical safety and helps extend equipment service life.

If you are looking for red prepreg DMD or white DMD materials, please feel free to contact us for detailed specifications, samples, and professional selection support.