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DMD insulation paper stands out as a premier choice for electrical insulation in motors, generators, transformers, and power‑electronics. Its unique three‑layer “fleece‑laminate” construction combines exceptional mechanical durability with superior dielectric and thermal performance. This guide centers on everything you need to know about DMD paper—how it’s made, why it works, where it excels—and then briefly surveys other high‑performance insulation papers for edge‑case applications.
DMD, short for Dacron‑Microporous‑Dacron, is a composite laminate consisting of:
Central Polyester Film (PET): A moisture‑barrier film (12–20 µm) providing dimensional stability.
Non‑woven Polyester Fleece Layers: Bonded to both sides of the film with a heat‑resistant adhesive, offering tear resistance and varnish absorption.
This structure delivers a smooth finish for easy insertion and superior varnish uptake, while resisting tearing, moisture, and heat.
Thermal Classes:
Class B: up to 130 °C
Class F: up to 155 °C (most common)
Class H: up to 180 °C (for extreme conditions)
Dielectric Strength: ≥ 60 kV/mm; breakdown voltages range 6–12 kV depending on thickness (0.15–0.40 mm).
Mechanical Durability: Remains cohesive through hundreds of flex cycles; tensile strength typically > 200 N/10 mm even after heat aging.
Moisture Resistance: PET core limits water uptake, preserving dielectric performance in humid environments.
Motor Slot Liners & Wedges
Thin grades (0.10–0.23 mm) precisely fill stator slots and act as wedge inserts to secure windings.
Turn‑to‑Turn & Layer Insulation
Thicker grades (0.30–0.90 mm) protect winding layers in high‑voltage motors and generators.
Dry‑Type Transformer Barriers
High mechanical strength supports automated stacking and coil encapsulation.
Ground Wall Insulation
Maintains consistent spacing and insulation between high‑voltage components.
Custom Formats
Rolls, sheets, or tapes tailored for hand winding or high‑speed CNC insertion.
Match Temperature Class: Choose Class F for most industrial motors; Class H for sustained high‑temperature operation.
Optimize Thickness: Thin strips for tight slots; thicker sheets for inter‑layer or ground‑wall use.
Check Certifications: Look for UL 1446, IEC 60085, CE marking, or regional standards like JB/T 4060.
Assess Surface Finish: A smooth, varnish‑absorptive surface enhances bonding and impregnation.
Consider Roll Width & Supply: Standard widths near 980–1 000 mm, with custom cutting available.
While DMD paper excels in versatility, sometimes specialized materials are needed:
Nomex Aramid Paper: Class H (180 °C) aramid fiber fleece with exceptional tear resistance and flame retardancy.
Polyimide (PI) Composite: High‑temperature film/fleece laminates (180–220 °C) with ultra‑high dielectric strength and chemical resistance.
Mica‑Based Paper: Rigid, multi‑layer mica/fleece laminates offering arc‑fault protection up to Class R (200 °C).
Glass‑Fiber Reinforced Paper: Class F/H glass‑fiber mats or films for high stiffness, tracking resistance, and moisture tolerance.
Use these alternatives only when DMD’s balance of properties doesn’t meet extreme temperature, chemical, or mechanical demands.
For most electrical insulation challenges—whether winding a precision motor or building a robust dry‑type transformer—DMD insulation paper remains the go‑to solution. Its three‑layer polyester/fleece laminate delivers the ideal mix of dielectric strength, thermal stability, and mechanical resilience. By selecting the right class, thickness, and finish, and understanding when to pivot to specialty electrical insulation papers, engineers can ensure optimal performance and longevity in even the most demanding applications.
