What is Hollow Fiber?
Hollow fiber is described as a filament with a hollow core. They can be of different types including hollofil which is a polyester lagging with a single hollow space through the core of each fiber. Hollofil 2 has four hollow spaces inside it, thus, it is better with the insulative characteristics than the hollofil 1. Another type of hollow fiber is hollow filament which is a synthetic continuous fiber with a single continuous core (Maitra, 2007). This article will discuss hollow fiber, touching on its specific uses as far as clothes are concerned.
The hollow fiber shows unusual liquid retention properties. The reason for such a property may be attributed to the microspores that are formed during the forming process and especially at the final stage by dissolution of a hydrophilic chemical as it is explained in the section two below (Berkowitch, 2000). This makes the fiber very absorbent of sweat without changing in diameter or mass and weight. The hollow fiber garments also dry fast because they store liquid intramolecularly and not between the molecules as in the case of solid fibers and especially natural fibers. The total voids to mass ratio content makes the fiber have good heat retentive properties when dry (Berkowitch, 2000).
How to Make a Hollow Fiber
Hollow fiber spinning processes can be categorized into extrudate and quench type. When the polymers are insolvent the polymer extrudate process is used and is known as melt spinning. On the other hand, use of a solvent in the polymer to form a polymeric solution is known as the quench type. The quench type may be either dry or wet. This depends on the fact that the quench may be in liquid or in gaseous form (Tao, 2001). The form of solution spinning known as wet spinning indicates that the polymeric solution passes through an aqueous solution/liquid after coming from the spinneret. In dry process, the polymer is passed through a gas quench bath.
The manufacturing processes in production of hollow fibers variance is discussed below. Synthetic polyesters which have more than one polymer content are produced by melting usually in the ration of 1:1 and then spinning them at a high rate in a ring spinneret, heating them at 120 degrees Celsius and cutting them and giving them hollowness to solid ratio of 5 to 30 percent (Tao, 2001). Acrylic fibers can also be produced as hollow fibers by the process of wet or dry spinning or as multi components having a soluble core which his dissolved to yield the hollow structure in form of an inner linear continuous channel.
Hollow acrylic fibers can also be produced by spinning a liquid containing acrylonitrile-methacrylic acid polymer as a casing and polyvinyl alcohol as center. This is usually used in composite material. Hollow acrylic fibers are used in making insulative garments. They are used as antecedents to carbon fibers because they disperse heat more effectively and normally than if they were not hollow (Tao, 2001).
In all the above processes, the polymer solution or melt passes through an annular region with a fluid known as the bore liquid which can be in liquid or gaseous form. The bore liquid helps in making the fiber to remain open. At the raised room temperature, the dilute polymer is extruded together with a gas such as nitrogen. As the emerging film moves through the air, it cools and looses the liquid solvent due to the evaporation before entering the liquid bath that cannot dissolve it. The fiber solidifies quickly the polymeric fibers are formed showing the microstructure properties that defines it as hollow fiber (Su, 2007).
General Uses of Hollow Fiber
Some use of hollow fiber extends beyond the textile industry although the textile industry is credited with innovation of the idea. One of the uses of hollow fiber is in the automotive industry where the fiber is used to make fabric that is used for deafening sound (Tao, 2001). The hollow fiber fabrics can absorb sound at a higher rate than the normal solid fibers. They are also easy to clean and can be used for car interiors. Due to their thermal insulative properties and a lustrous finish, the hollow fibers are used to decorate the inside of the car as they serve two purposes simultaneously, decorative and thermal insulation (Ibrahim, 2011).
The hollow fibers have also been used to make tents and sleeping bags. This is because they have a low adherent to dirt and water. They have also exhibited properties of resistance to wetting because the residual solvent that is used during spinning evaporates at a high temperature, thus, forming a coat with wax properties on the surface of the fibers. This gives the fibers its resilience to wetting property. In very cold months the fiber has been used to make house insulation, bed stuffing material and generally used in making fabrics for keeping oneself warm. Their insulative property comes from the fact that there is a hollow gap in the middle of the fiber which basically is filled with air or liquid (Delmon, 1998). This means that warm air cannot be conducted through the void once it is generated by the body or in the house or car.
Special spinning of hollow fiber has been done in the medical field to aid in dialysis of the kidney. The dialyzer is made from hollow fiber which allows the blood to pass through as it gets cleaned. The fibers, however, are especially span to give them the desired quality that can be used in dialysis (Delmon, 1998).
Hollow fiber is used in making fabrics for use in areas where they are not supposed to withstand the pressure but should regain their shape when the pressure applied is removed. They are, therefore, very suitable for use in stuffing of pillows and making the inside fabric of shoes especially those designed for the cold seasons (Berkowitch, 2000).
Hollow fibers are used in drinking water treatment. They are usually either bundled together longitudinally and put in a pressure vessel and potted with resin on both ends. They may also be mounted vertically and submerged in a basin that does not utilize pressure. These configurations can also be mounted horizontally. In the environmental and waste water management fields, the hollow fiber has been used in waste water treatment. This is another use where a bundle of hollow fibers is used to form a membrane for separation of gases in the industrial gas separation processes. For this, the material used does not need to be able to withstand pressure. The environmentally friendly synthetic fibers are, therefore, used also helping the environmental degradation control (Tao, 2001).
The hollow fiber textiles have been used in computing industry in the manufacture of optic fibers. This is because the knowledge on hollow fiber in textile has been used to produce the same kind of application but one with a larger core to carry wires (Su, 2007).
Hollow Fiber Use for Sports Wear
Hollow synthetic fibers are particularly used in making underwear and sportswear. This is because sportswear is leisure clothing which considerably extends its scope. The microspores in the fiber used to make the fabric absorbs seat. This it does without change in mass because it is usually diffused through the hollow centre and also leaves the surface dry. The hollow centre acts as the tank for sweat. They are also used in sports wear because they dry fast. The pore to the surface area ratio is very small and, thus, the fabric is able to dry very fast.
The sportswear industry has the hollow fiber as its secret to success because the pore surface reflects light in different directions hence giving the fabric a lustrous finish. When dyed, the result is a fabric which shines when the light bounces on it. This is good for the sportswear industry because the luster effect is used as an advertising platform. People want to see the player in lustrous clothing.
The eye catching luster and the ability to retain color and reflect it brightly is good for sportswear, because bright colors help to keep one’s spirit up during games. The fabric is also usually very light weight. Due to the numerous pores in the fiber and the hollow core, the solid diameter of the fiber is greatly reduced for a large mass of fiber. This in turn translates into fabric that is light wear perfect for sportswear.
The other good quality of hollow fabric for use in the sports wear industry is the lack of ability to retain liquids. No one would want a fabric that becomes heavy with retention of liquid. Even when playing in the rain, the fabric should remain as light as possible (Tao, 2001).
The use of synthetic polyester for use in sportswear is limited to the clothes only but also to the footwear. This is because hey are very light and especially very perfect in games that need the players to move at high speed. The fact that it is a hollow polymer also makes it more durable (Tao, 2001). This is because the hollow polymers bend under pressure but retain their natural shape when the pressure is removed. This is perfect for footwear in the sports industry.
The ability of hollow fiber to stretch is another desirable character for using it in making sports wear. In he sports career, a garment that suits the body is preferred. This is because it should be possible for the garment to allow free movement without becoming a hindrance to the actions of the wearer (Delmon, 1998). This is why the garment should be made with fabric that is able to stretch, thus, attaining a close fit without making the wearer feel uncomfortable.
The ability of a fabric to regulate temperature with given weather conditions is necessary in design of sportswear. Synthetic hollow fibers are in a position to provide such a property in a fabric due to their structure. They can be able to retain heat if necessary or dissipate it through the hollow core. When it is used in cold, the air or liquid trapped inside the core condenses, thus, making it impossible for heat to escape. On the other hand, in temperate areas, the content of the core expands, thus, being in a continuous motion and in the process affecting a cooling effect (Tao, 2001).