Introduction, Bonding and Stabilization of web, Mechanical bonding,Process

2. Dry laid Nonwoven
Introduction
This technique involved the following steps
Fibre Selection
These fibres are long enough to be handled by conventional spinning
equipment. The fibres are 1.2 to 20cm or longer, but not continues.
Fibre Preparation
Fibre preparation consists of mechanical and pneumatic processes of handling
from the bale to the point where the fibre is introduced into the web-forming machine.
 Bale opening
 Blending
Coarse opening
Fine opening Web-former feeding

3. Web Formation
There are two types of web formation methods are followed here
Mechanical web formation (Carding or Granetting)
Aerodynamic web formation (Air – laid)
Layering
Web formations can be made into the desired web structure by the layering of the
webs from either the card or garnet. Layering can be accomplished in several ways to each
desired weight and web structure.
Longitudinal Layering
More then once cards are involved in here. Carded webs from all the
cards(placed in a sequence one after the other) are laid above one another on a conveyor
belt and later bonded. Properties of the bonded webs are anisotropies in nature because of
the unidirectional arrangements of fibres. This technique can only be used for making light
textiles.

4. Cross Layering
It can be done by using two different devices (cross lappers); vertical and
horizontal cross lapper. Vertical lapper consists of a pendulum conveyor after the doffer
roll on a card pendulum conveyor reciprocates and lays the carded web in to folds an
another conveyor belt.
Perpendicular Layering
This technique has an advantage over longitudinal and cross layering because of
the perpendicular and oriented fibres in the fabric. The bonded web have high resistance
to compression and show better recovery after repeated loading.

5. Bonding and Stabilization of Web
Mechanical Bonding
1. Needle Punching
Needle punching is a process of bonding nonwoven web structures by
mechanically interlocking the fibres through the web. Barbed needles, mounted on a
board, punch fibres into the web and then are withdrawn leaving the fibres entangled.
The needles are spaced in a non-aligned arrangement and are designed to release the
fibre as the needle board is withdrawn.
Needle punch Process
The needle punch nonwovens are created by mechanically orienting and
interlocking the fibres of a spun fabric or carded web. This mechanical interlocking is
achieved with thousands of board felting needles repeatedly passing into and out of the
web.

6. The needle board
The needle board is the base unit into which the needles are
inserted and held. The needle board driven roll then fits into the needle
beam that holds the needle board into place. These are typically driven
rolls and they facilitate the web motion as it passes through the needle
loom.

7. The bed plate and stripper plate: The web passes through two plates a bed plate on the
bottom and a stripper plate on the top . Corresponding holes are located in each plate and it
is through these holes the needles pass in and out. The bed plate is the surface the fabric
passes over which the web passes through the loom. The needles carry bundles of fiber
through the bed plate holes. The stripper plate dose what the name implies; it stripes the
fibers from the needle so the material can advance through the needle loom.
The correct felting, needle can make or break the needle punch product. The
proper selection of gauge , barb, point type and blade shape (pinch blade, star blade,
conical) can often give the needle puncher the added edge needed in this competitive
industry.

8. Stitch bonding
Stitch bonding is a method of consolidating fibre with knitting elements with or
without yarn to interlock the fibres. There are a number of different yarns that can be
used. kevlar is used for strength in the fabric for protective tests. Lycra is used for stretch
in the fabric. Home furnishing for a big market for this fabrics other uses are vacuum
bag, geo textiles, filtration and interlinings. In many applications stitch – bonded fabrics
are taking the place of oven goods because they are faster to produce and, hence, the cost
of production is considerably less.
Thermal Bonding
Thermal bonding is the process of using heat to bond or stabilize a web
structure that consists of a thermoplastic fibre. All part of the fibers act as thermal binders,
thus eliminating the use of latex or resin binders. Thermal bonding is the leading method
used by the cover stock industry for baby diapers. Polypropylene has been the most
suitable fiber with a low melting approximately 165 0 c. It is also soft to touch. The fibre
web is passed between treated calendar rollers, where the web is bonded.

9. In most case point bonding by use of embossed rolls is the most desired method, adding
softeners and flexibility to the fabric. Use of smooth rolls bonds the entire surface of the
fabrics increasing the strength, but reduces drape and softness.
Chemical Bonding
Bonding a web by means of a chemical is one of the most common methods of
bonding. The chemical binder is applied to the web and is cured. The most commonly
used binder is latex, because it is economical easy to apply and very effective. Several
methods are used to apply the binder and include saturation bonding, spray bonding print
bonding and foam bonding.
Saturation
Foam bonding
Spray bonding
Print bonding
Power bonding

10. Hydro Entanglement
Hydro entanglement is a process of using fluid forces to lock the fibre together.
This is achieved by fine water jet directed through the web which is supported by a
conveyor belt. Entanglement occurs when the water strikes the web and the fibers are
deflected. The vigorous agitation within the web causes the fibres to become entangled.