Aerodynamic Web formation (Air-lay)

Non woven fabric

Nonwoven Fabric is a fabric-like material made from fibers, bonded together by chemical, mechanical,heat or solvent treatment. 

Web formation

Nonwoven manufacture starts by the arrangement of fibres in a sheet or web. The fibres can be staple fibres packed in bales, or filaments extruded from molten polymer granules.

Methods of forming a web

   — Drylaid

   — Spunmelt

   — Wetlaid

   — Other techniques

 

Aerodynamic web formation 

•       Drylaid web forming method.

•       Short fibres are used to form the web.

•       Compared with other drylaids, airlaid webs have a lower density, a greater softness and an absence of laminar structure 

 Aerodynamic web forming machine

 Process

• Lap or plied card webs are fed by a feed rollers.

• The fibers are separated by a licker-in or spiked roller and introduced into an air-stream.

• By the force generated by the air stream (suck or blew), single fibres are collected to form a web on a perforated surface of the cylinder.

• The web is delivered to a conveyor for transporting to the bonding area. 

 Features of the Air-laid

• The length of fibers used  varies from 2 to 6 cm. 

• The shorter lengths allow higher production speeds. Longer fibers require higher air volumes to avoid tangling.

• Due to uniformity problems, it has not been practical to make isotropic webs lighter than 30g/m2.

• Air-laying is slower than carding ,hence more expensive.

Advantages

•         Isotropic structure of the web.

•         Vast webs can be produced.

•         Wide variety of processable fibers such as natural, synthetic, glass, steel, carbon, etc.

•       Possibility of processing waste fibres 

Disadvantages

• Low level of opening fiber material by licker-in.

• Variable structures of web in width of layer due to irregular air flow close to walls of duct.

• Possible entanglement of fibers in air stream.