**8. Engineered fabrics by fiber entanglements**

There are three methods of producing engineered fabric by fiber entanglements; needle punch, hydroentanglement and stitch bonding. These three methods are based on fiber entanglements and frictional behavior of fibers and conceptually known as mechanical bonding. Out of these three techniques needle punch is most popular and simplest one [40].

#### **8.1. Needle punching**

The concept of needle punching is quite clear and simple. In this method the batt is passes between two stationary plates, the bed and stripper plates. While between the plates the batt is penetrated. The needle density remains up to about 4000 m−<sup>1</sup> width of the loom. The design of penetrating needle plays major role in fiber entanglement. Needles are generally made triangular in shape and have barbs cut into the three. As the needle goes down into the batt the barbs traps some fibers and pull them through the other fibers to get it entangled.

When the needles return back in upward direction, the fiber loops formed during downward movement of needles tend to remain in position, because they are released by the barbs. This downward penetration of needles takes place repeatedly which makes the batt much denser and finally needle punched structure manufactured [41].

#### **8.2. Hydroentanglement**

The hydroentanglement process of engineered fabrics manufacturing was developed by DuPont in 1960. This process is quite similar to needle punch process. This technique is used to entangle the fibers of lightweight batt. In this process very fine nozzles are used to inject the water in the form of fine water streams or droplets. Number of fine nozzles is situated at the edges of batt. The water stream passes through the perforated screen to remove the used water. The fiber which come in the contact of water get wetted and its total momentum goes compare to other fibers and these fibers get entangles with other fibers of the batt. Water cleanliness, pH and temperature are critical issues to be taken care during the manufacturing. This process is capable to produce engineered fabrics for wipes, surgical gowns, disposable protective clothing and backing fabrics for coating applications [42].
