How are nonwoven fabrics made and what types are there?

Through mechanical, thermal, or chemical processes, nonwoven fabrics are created. These substrates are flat and porous sheets made of single fibers, melted plastic, or plastic films. Nonwoven fabrics, as the name suggests, are not created by weaving and do not require the conversion of fibers into thread.

Variations in fiber selection, web formation, bonding, and finishing result in products with unique characteristics, making them suitable for various fields such as the hygiene and healthcare market, clothing, automotive, filtration, construction, and agriculture.

We can divide the technologies currently used to produce nonwoven fabrics into six types:

  1. Airlaid: This method uses air to form a homogeneous web composed of randomly oriented short fibers. The subsequent bonding of the fibers, deposited on an air-permeable conveyor belt, can be done through heat (thermobonding airlaid – TBAL), hydrogen (hydrogen bonding airlaid – HBAL), latex (latex bonding airlaid – LBAL), or a mixed LBAL + TBAL process.
  • Air-through bonding

A thermal bonding process involves the use of hot air on the surface of the nonwoven material, resulting in a voluminous, soft, and uniform material with high tensile strength. This process does not use chemical binders and is the only type of thermal bonding process that exposes the entire product to a uniform temperature.

  • Meltblown

Nonwoven fabric obtained through a spinning process called “spunbonding.” Melted polymeric fibers are passed through a spinneret to form long, fine fibers, which are then stretched and deposited onto a conveyor belt with hot compressed air, creating the fabric. Spunbond nonwoven fabrics are composed of extremely long and lightweight fibers, exhibiting high filtration capacity.

  • Spunlace

Nonwoven fabric obtained through a bonding process of fibrous webs, either wet or dry, obtained through carding, air bonding, or wet bonding. The process, known as spunlace or “hydroentangling,” involves fine jets of high-pressure water penetrating the web, hitting the conveyor belt, and bouncing back, thereby causing the entanglement of fibers.

  • Spunlaid (or Spunbond)

Spunbond nonwovens, also called spunbond, are materials composed of extremely fine filaments. They are manufactured through a process that involves polymer extrusion to form continuous filaments, which are then conditioned, stretched, and deposited onto a conveyor belt to create the fabric. The filaments are chemically, mechanically, or thermally bonded to obtain the final product. Polypropylene-based spunbond is the predominant material for diapers and feminine hygiene products, as well as medical clothing.

  • Spunmelt/SMS

Spunbond is often combined with meltblown nonwoven to create a layered product called SMS (spun-melt-spun). Completely made of PP (polypropylene), SMS nonwovens are water repellent and can be used for disposable applications. Meltblown is commonly used as a filtering material due to its ability to capture very fine particles.

  • Wetlaid

Production technology similar to that used in paper manufacturing characterizes nonwovens of this type. These nonwovens differ from wetlaid paper in that more than 30% by weight of their fibrous content is composed of fibers with a length-to-diameter ratio greater than 300, while the density is less than 0.40 g/cm³. Wetlaid is commonly used to manufacture products such as tea bags, coffee filters, and disposable wipes.

Among the key characteristics of nonwoven materials is elasticity, leading to progressive narrowing of the initial web width (neck-in) from the winding phase to the final product. In this regard, it is necessary to distinguish the specific characteristics of the two main types of nonwovens: spunlaid and spunlace.

Spunlaid, characterized by a random positioning of its fibers, is more resistant to traction and, for this reason, undergoes greater contraction compared to spunlace. For instance, an initial web width of 3600 mm results in final rolls with a width of 3200 mm.

Spunlace, on the other hand, is composed of fibers oriented in the machine direction due to the use of carding machines in the formation process. This makes it resistant to traction in that direction and, therefore, less prone to contraction.

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