Composite Yarn Manufacturing & Their Applications

  Definition

         Composite yarns are structures consisting of at least two strands, one forming the center axis, or core, of the yarn, and the other strand forms the covering or wrap One strand is usually composed of staple fibers and the other is of filaments

 Classification

 Covering Process

• Covered yarns have a central yarn (core) which is completely covered by fiber or another yarn
• The core might be an elastomeric fiber, such as rubber or spandex, or a hard fiber such as polyester or nylon.

 Single Covering Process 

Double Covering Process

 

Core Spun Yarn

Definition

• Core-spinning is a process by which fibers are twisted around an existing yarn, either filament or staple spun yarn, to produce a sheath– core structure in which the already formed yarn is the core. 

• Core-spun yarns are two-component structure with Core and sheath. Generally continuous filament yarn is used as core and  the staple fibers used as sheath covering.                                

 Method of production

The production of Core-spun yarns done successfully by many spinning systems. 

1.Conventional core spinning attachment with ring spinning systems

2.Core-twin spinning system

3.Composite electrostatic spinning system

4.Rotor spinning system

5.Friction spinning system and

6.Air jet spinning system

 Conventional core spinning attachment in Ring spinning

 The conventional ring spinning is simple and economy but  the core positioning in the center is difficult and major strip back problem may arise during subsequent process and the core filaments get twisted

  Effect of Process variables on Ring Core-spun yarn properties   

    The process variables that affect the core-spun yarn properties are: 

1) Core - sheath ratio

2) Pre-tension applied to the core materia

l3) Spinning draf

t4) Number of roving feed and

5) Twist

 

Core Twin Spinning system   and Composite yarn by Electro static filament charging method 

                                    

 

        A minimum pre-tension is necessary to avoid filament flung out in to the rotor-collecting surface. The core is not twisted during this process. It is economical to produce coarse core-spun yarns through rotor machine than the ring core-spun yarns Any types of material, including metallic wires high tensional rigidities can be used as cores                                                                                                                Core-spun yarn production by MJS spinning system 

 

        The Air-jet spinning could be used for producing core yarns after optimizing process parameters. A relatively higher first nozzle pressure is advantageous for improving sheath-slippage resistance. The use of higher spinning speed and wider condenser markedly improves the tenacity, breaking extension, initial modulus and sheath-slippage resistance and affects the yarn hairiness, mass irregularity and flexural rigidity. However, yarn properties deteriorate at high spinning speed especially for finer yarns.   

           Core-spun yarn production by Friction spinning system

         The sheath fires are attached to the core fires by false twist generated by the rotating action of the drums. In DREF III the core positioning can be set accurately and used to produce the industrial and conductive yarns. 

 

         Strength of the DREF III core-spun yarns have direct relationship with the strength of core filaments and number of sheath fires that are active in generating radial pressure due to their structural helical configurations

         The effectiveness of wrapping of sheath fires depends on physical and mechanical characteristics of fires, configuration, length variations, firmness of the wrap and wrap angle

 WRAPPED YARNS

 Filament-Wrapped Spun Yarns

 Untwisted, parallel staple fiber strand in the center of the yarn, and a filament wrapped around the center strand. Combines spun yarn aesthetics with filament yarn durability.  Wrap spinning with a filament replaces the insertion of twist to produce a yarn. It is also economical and has good evenness, strength, elongation, appearance, and abrasion properties   
                                                                        
      Filament-Wrapped with Staple Fibers  

  •Bundle of filaments wrapped with staple fibers.

–Coarse filaments - strength

–Fine broken filament - softness 

  •Production of these yarns is very fast.  These yarns give better texture and hand to fabrics

Filament-Wrapped with Filament Yarns • 

•For better strength purposes 

• Heavy applications 

•Speeder than conventional ring spinning•Ease of core slippage -
Composite properties, depended on filament frictional properties &   yarn packing density.