Nonwoven, or Vliesstoff in German, is a sheet material made of fibres that are bonded without weaving or knitting, using mechanical, chemical or thermal processes. Standard ISO 9092 defines this term precisely. Technical nonwovens weigh between around 10 and over 300 g/m², and in insulation laminates such as DMD they form the outer layers of a build 0.15 to 0.40 mm thick. Most search demand for nonwoven fabric points to fashion, hygiene products or construction fleece, a field GOBA does not serve. Our stake in nonwovens lies in the insulation materials for motors and transformers: as a carrier layer in laminates, as an impregnation aid in motor windings and as a filter medium. This page separates nonwoven from woven and knitted fabric, explains manufacture and fibre materials, and shows where it actually does the work inside an insulation system.
How does nonwoven differ from woven and knitted fabric?
The difference lies in the structure. In a woven fabric, warp and weft threads cross each other, in a knit, loops hold the material together. A nonwoven instead starts as a loose web of fibres, a fibre batt, which only a bonding process turns into a usable material. Structurally, it therefore sits between paper and textile: randomly oriented fibres like paper, combined with the flexibility and tear strength of a textile. That combination is exactly what makes nonwoven useful for two very different jobs, filtration and insulation, while it stays inferior to a woven fabric wherever high mechanical loads dominate.
How is nonwoven fabric manufactured?
Manufacture always runs in two stages: forming the fibre web first, then bonding it. Both stages together set the density, strength and absorbency of the finished nonwoven.
| Process | Principle | Typical result |
|---|---|---|
| Carding | Staple fibres are mechanically aligned on rollers | Staple fibre nonwoven for insulation and padding |
| Spunbond | Polymer is extruded and spun directly into continuous filaments | Technical nonwovens with high tear strength, geotextiles |
| Meltblown | Molten polymer is blown with hot air into microfibres down to about 1 µm | Fine filter nonwovens with high separation efficiency |
| Wetlaid | Short fibres are dispersed in water and laid down like paper | Speciality papers, glass and ceramic fibre nonwovens |
| Needle punching | Barbed needles mechanically entangle the fibres | Needle felt, insulation and carrier nonwovens with high tensile strength |
| Thermobonding | Fibres are partially melted and fused together | Polyester nonwoven for DMD outer layers |
For insulation laminates, thermal bonding is the usual choice: it delivers an even, laminatable nonwoven with defined porosity, the exact property that matters for resin absorption later on.
Two figures describe a technical nonwoven completely: grammage in grams per square metre and thickness. Technical nonwovens range from around 10 g/m² for fine filter media to over 300 g/m² for thick padding and carrier nonwovens. A higher grammage absorbs more resin later on, but also thickens the finished laminate build, a trade-off that the design has to weigh case by case.
Fibre orientation also decides strength in one direction versus another. In a randomly laid nonwoven, tear strength spreads evenly in all directions, isotropic behaviour. Cross-lapped nonwovens stack several layers at an angle to each other and reach higher strength in both machine and cross direction, at the cost of a more demanding process. For a laminate such as DMD, simple random laydown is enough, because the film layer already carries the load-bearing strength.
Which materials are processed into nonwoven?
The raw fibre determines temperature resistance and field of use. Three fibre types dominate in electrical engineering.
| Material | Continuous temperature | Typical use |
|---|---|---|
| Polyester (PET) | up to about 130 °C, class B | DMD laminate, polyester film composites, standard motors |
| Aramid, e.g. Nomex | 220 °C and higher, class H | Traction motors, see Nomex and aramid paper |
| Glass fibre | above 250 °C, non-flammable | Fire protection, high-temperature insulation, see flat insulating materials |
| Cellulose, natural fibre | up to about 105 °C, class A | Basic padding and packaging applications |
Nonwoven as an insulating material: the carrier layer for resin
In electrical insulation, nonwoven almost never provides the insulating function itself. A smooth film or paper does that job, the nonwoven instead delivers mechanical strength and absorbency. DMD laminate shows this clearly: two outer layers of polyester nonwoven, commercially often called Dacron, sandwich a middle layer of polyester film. The film carries the dielectric strength, the nonwoven absorbs the impregnating resin later on and bonds firmly with the winding. Layer structure and thickness, typically 0.15 to 0.40 mm, are covered in the article on DMD laminate.
This resin-carrier function drives the material choice in practice. Windings impregnated through the VPI process need an insulating material that absorbs the resin and bonds firmly with it, a smooth film without a nonwoven layer cannot do that. That is why GOBA frequently specifies nonwoven-film laminates such as DMD or NMN for slot insulation and phase insulation, instead of plain film.
Nonwoven should not be confused with the highly compressed cellulose boards used as solid insulation in the transformer: transformerboard and pressboard are densely pressed board, not a loose fibre structure. Both material groups come from the same cellulose family, but their mechanical properties are worlds apart.
Nonwoven as a filter medium: distinction from filter nonwoven and Viledon
Besides insulation, filtration is the second major technical field for nonwoven. Its fibre structure forms a three-dimensional pore system that separates particles by depth filtration, rather than retaining them at a defined mesh size like a screen. Readers looking for filter nonwoven in air or liquid filtration find the technical detail in the article on filter nonwoven, branded products from Freudenberg are covered in the article on Viledon. GOBA slits and converts filter nonwoven as a contract slitting service to customer dimensions.
Further technical applications of nonwoven
Beyond insulation and filtration, nonwoven turns up in several other fields:
- Insulation in construction and automotive, usually glass or PET based
- Core material in sandwich and composite structures, absorbing resin and saving weight, see also composite slitting
- Protective and separator layers during transport and assembly of sensitive parts
- Hygiene products and medical disposables, outside GOBA's focus
This breadth explains why generic search queries for nonwoven and nonwoven fabric spread across industries that have nothing to do with electrical insulation. GOBA focuses on the technical role of nonwoven in insulating materials and composites for the electrical industry.
Nonwoven, woven fabric and felt compared
| Property | Nonwoven | Woven fabric | Felt |
|---|---|---|---|
| Fibre orientation | random or layered | crossed warp and weft threads | fulled, random |
| Strength | medium, direction dependent | high, defined | medium, isotropic |
| Cost | low | higher due to weaving process | medium |
| Typical use | insulation laminates, filters, padding | glass fabric laminates, high-load parts | gaskets, damping |
Is nonwoven enough as an insulating material on its own, or does it need a laminate?
Pure nonwoven has no meaningful dielectric strength on its own. Its open pore structure lets air, and with it moisture, pass through, and both reduce electrical strength. Applications under voltage load therefore always need a combination with a closed film or paper, as in DMD or NMN laminate. As a plain carrier layer for resin, as a cushioning or damping layer, or as a filter medium, nonwoven works well on its own. Anyone unsure whether an application calls for pure nonwoven or a laminate should clarify the voltage level and expected moisture exposure before choosing a material.
Cutting nonwoven: roll and contract slitting
Thin nonwoven tends to fray when cut, because the loose fibre ends at the cut edge do not separate cleanly the way a film does. A clean cut therefore needs the right blade geometry and cutting speed, matched to fibre type and grammage. GOBA slits nonwoven and nonwoven laminates through contract slitting, from roll goods to finished cut parts, on rolls or as individual pieces to drawing.
GOBA Takeaway
Nonwoven rarely provides the insulating function itself. It is the carrier layer that makes a laminate processable and impregnable in the first place. GOBA has worked with this role for decades through our insulation materials for motors and transformers. We slit and convert technical nonwovens and nonwoven laminates through contract slitting to customer dimensions, from the roll to the finished cut part. For special constructions and small quantities, talk to us about custom products.
