PRODUCTION OF POLYPROPYLENE FIBRES
The polypropylene fibres or continuous filaments are produced by using melt -spinning process.
The polymer chips are heated above melting point temperature with the help of hot air or another heating arrangement.
In this way, molten polymer is obtained. Now this molten polymer is sent to the spinning system with the help of geared feeding pump, here the molten polymer is homogenised first and then it passes through a filter.
Now, the filtered molten polymer is fed to spinnerets. When the molten polymer comes out from thin holes of spinnerets, the newly formed filament is hot.
There is a need to cool these filaments. These filaments get quenched into the cold air, where 3 cubic metre/ minute cool air is passed through the quenching zone without damaging the filaments.
These filaments are coarse. They are passed through drawing rollers. “The filaments are hot stretched many times of their original length”.
Now, these filaments are passed through crimping devices to improve the bulkiness. Heat-setting treatment is applied to these crimped filaments.
These filaments can be wound onto bobbins or spools. The filaments are also cut into pieces as per requirement. These cut filaments are used to produce spun yarn.
BIAXIALLY ORIENTED POLYPROPYLENE FIBRE
“The polypropylene film extruded and stretched in both the machine direction and across the machine direction it is called biaxially oriented polypropylene”. Bi-axial orientation helps to improve the strength and clarity of polymer. It is widely used as a packaging material for packaging products such as foods, fresh produce and confectionery. This Polypropylene gets to coat, print and laminate easily. “This process is normally called converting”. It is normally produced in large rolls which are slit on slitting machines into smaller rolls for use on packaging machines.
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