The Working Principles of Non-woven Fabric Net Curtain

After stretching and cooling, fluffy filament must be continuously and evenly made into the network. Some netting processes do not belong to the weaving cloth craft. In order to form the network, the electrode plate is decorated under the setting net curtain to produce a electrostatic field with opposite polar of the filament to attract filament and accelerate its movement to the setting net curtain. The key to form the network is to control the movement of the filament bundle. Basically there are the following two kinds of control mode.

a.Air flow control
It is one of the simplest control methods. It takes use of regular exercise of the air flow formed in the stretch pipe at the exit of filament bundle to make the filament bundle spread on setting net curtain in a certain way (such as circular motion) or takes use of the side airflow to control filament bundle to achieve reciprocating laying. In the process of the laying, filament bundle inevitably tends to form some directional fiber arrangement. In order to obtain mixed and disorderly arrangement of fabric, in a lot of nonwoven fabric net forming processes, multiple sets of spinneret arranged in cross or oblique way are used to get mixed and disorderly arrangement of the fibers as much as possible and improve the evenness of fabric.

b.Mechanical control
It mainly uses roller and rotor control to achieve the reciprocating motion of stretching wire tubes, so as to spread the filament bundle regularly on the setting net curtain to form a fiber network. Some other craft makes use of the spinning or oscillating methods to form the network.

Generally speaking, regardless of the air flow or mechanical control, the quality of the network formed is no match for the dry forming fabrics. The lower the quality of the net fabric has, the higher the irregularity of the fiber network has. Even for those thin fabrics with high quality, their fabric irregularity is close to 10%. In addition, although the fabric arrangement is mixed and disorderly, the longitudinal and transverse strength ratio shows great difference. In some areas the longitudinal and transverse strength ratio is able to reach 1.5:1, however, in some other areas, the ratio may be more than 5:1. Nowadays, with the advance of the network forming technology, some companies have produced nonwoven fabrics with good uniformity, which are close to the quality of the dry forming fabrics.

Through the network forming process, polymer slice has turned into filament fabric, but it is still semi-product in the process of nonwovens production, which still needs to be reinforced through mechanical, chemical or thermal methods. In most of nonwovens network forming processes, in order to achieve the purpose of high-speed production, they adopt the method of hot glue or self bonding to reinforce fabrics. For example, polyamide 66 is used as polymer material and HCI solution is used to deal with fabric to achieve the fabric adhesion. Some patent literature suggests to use mix SO2 - CI2, NO2, N2O3 or CI2 in fabric processing. The self bonding mechanism of HCI is that HCI and amide groups will form hydrochloric acid compounds to damage the hydrogen bonding between long chains and therefore form adhesion between fibers.

Polyolefin has now become the polymer mostly used in the nonwovens fabric network processing because of its low melting point. It is easy for the hot glue. Hot rolling mill or air dryer can be used for hot glue. The glue forms are point glue, surface glue and pattern glue. The network forming process using the two-component polymer (most of its shells are polyolefin) is very suitable for hot rolled or hot air bonded processing, and the non-woven fabrics produced in this way have good bonding structure.
In recent years, in order to expand the purpose of the nonwoven fabric, after the network forming process, mild hot rolled or acupuncture methods are used to pre-reinforce the fabric, and then mechanical reinforcement (such as acupuncture, spunlace, seam lawmakers) or chemical reinforcement (such as impregnation method, spray foam bonding, printing bonding, etc.) are taken. Among them acupuncture is widely used in the reinforcement.