1. FIBER
Prepared by- Mr. Vishal B. Thakare
Assistant Professor, PARUL UNIVERSITY
(M.Tech Chemical, SVNIT Surat)
vishalbt88@gmail.com
2. Fiber
Fiber -
Material which length is at least 100 times its diameter is
termed as fiber.
Artificial fibers can usually be made in any desired ratio of length
to diameter.
Natural fibers such as cotton wool are found with lengths 1000-
3000 times their diameter.
3. Denier-
It is unit of measurement used to determine the fiber thickness of
individual threads or filaments.
It is based on mass per length of yarn
Fabrics with high denier count tend to be thick, sturdy and
durable.
Fabrics with low denier count tend to be sheer, soft and silky.
4. Crimp –
Crimp is the waviness of a fiber.
It is measure of the difference between the length of the
unstraightened and straightened fiber.
Crimp can be artificially produced in fibers by suitable heat
treatment or by rolling them between heated, fluted rolls.
8. 1) Chemical stability -
All textile fiber must be stable to water, dry cleaning solvents,
dilute acids, alkalies and bleaches.
Close packing of the polymers prevents ready entry of
chemicals. More the polymer system is crystalline in nature
more will be the resistance of the fibers against degradation by
chemicals. Thus, many synthetic fibers are used in industry to
make filter fabrics and protective clothing. Fiber polymers
should be chemically resistant for a reasonable length of time
against the common degrading agents such as sunlight and
weather, common types of soiling, body exudations, laundry
liquors and dry cleaning solvents. The most required property of
chemically resistant polymers should be such that it should not
be toxic or hazardous to wear against human skin.
9. Polymer of fibers should be chemically resistant, but they should
not be inert. Chemical inertness of fiber polymers results in
detrimental effect on other fiber-forming requirements. The
polymers of chloro-fibers, fluorocarbon, polyethylene and
polypropylene may be regarded as chemically inert from a
practical point of view.
2) Length
Fiber polymers should be long. The length of polymers is directly
related to the strength of fiber by holding the crystalline regions
together.
10. 3) Linearity
Fiber polymer should be linear. Highly linear polymers will form more
crystalline regions, which results in a large number of inter-polymer forces of
attraction within the polymer system.
Branched polymers, cross linked polymers, or three dimensionally cross
linked polymer systems are not desirable for the production of textile fibers.
Polymers which are bulky or branched cannot pack close together, which
prevents the formation of crystalline regions in the polymer system of the
textile fiber. The inability to form crystalline regions means there will be less
forces of attraction exerting their influence to hold the polymers in an orderly
arrangement, thus resulting in a weak fiber.
11. • Many fiber polymers, which need to be linear, have side groups,
as distinct from branches. Side groups causes 'bulges' along the
polymer backbone, rather than the distinct projection of a branch.
Examples of fibers with the side groups are the nitrile group of
acrylics, the hydroxyl and methylol groups of the cellulose fibers,
and the hydroxyl and acetyl groups of ester-cellulose fibers.
12. 4) Hydrophilic properties
Fiber polymers should be hydrophilic. Polar nature of fiber and
amorphous polymer system of a fiber are responsible to absorb moisture.
Amorphous polymer system: Crystalline polymer system of a fiber does
not allow even very small molecules, such as water, to enter the fiber.
This explains the poor moisture absorbency of all synthetic fibers which
are very crystalline in nature. More the amorphous nature of fibers, such
as wool and viscose, more they are absorbent in nature.
Polar: Presence of certain chemical groups influences the moisture
absorbency for example, the hydroxyl or -OH groups of cellulose which
attract water molecules. A fiber is comfortable to wear if its polymer
system is made up of hydrophilic polymers, and the system allows the
entry of water molecules. Hydrophobic polymer fibers whose polymers
are non-polar are yet used as fibers for textile applications. In order to
make the textile materials of these fibers more water attracting, absorbent
and comfortable, hydrophobic-polymer fibers need to be blended with the
hydrophilic polymer fibers to get desired properties.
13. Examples: Hydrophobic-polymer fibers like nylon and polyester are
often blended with cotton, viscose or wool (e.g. two-thirds
polyester/one-third cotton blend). Blending improves the water
absorbency and comfort of their textile materials. Acrylics are
also hydrophobic polymer fibers. Knitted outerwear made of
acrylics is very popular; and it will be found that it is usual to
wear this non-absorbent knitwear over an absorbent or
hydrophilic-polymer fiber garment to counter or reduce potential
discomfort which might otherwise be experienced.
The hydrophobic nature of crystalline synthetic fibers gives rise to
static electricity. This can be undesirable during yarn and fabric
manufacture, as well as during garment manufacturing and
subsequent wearing of the apparel. In amorphous fibers there is
the absence of static electricity, usually due to more absorbency
of moisture. It is due to this reason that the amorphous fibers are
blended with the more crystalline fibers to make the crystalline
polymer system more comfortable to wear.
14. 5) Color
White or colorless fibers and filaments are preferred. Color of natural
fibers and delustred man-made fibers are white to off-white. Reason of
preference for white or colorless fibers is they can be dyed or printed
with any hue of color.
6) Translucency
A translucent fiber will transmit light but is not transparent.
7) Structure
For cotton, flax, viscose or wool it is possible to make a conclusive
identification by microscopic examination of the longitudinal and cross-
sectional structure of the fiber or filament. The individual
characteristics of the textile micro-structure influences skin contact
comfort. For example, the minute surface irregularities of the other-
wise regular and even fiber structure of cotton and silk make them
comfortable and pleasant to wear. In contrast, the extremely smooth,
even, regular surface structure of fibers such as nylon and polyester
results aesthetically un-desirable and uncomfortable against the skin.
15. 8) Fiber tenacity
Tenacity, or tensile strength, is the ability of a textile to withstand
a pulling force. The tenacity is measured by measuring the force
needed to break or rupture the fiber when both of its ends are in
clamp. Breaking tenacity for a fiber is the force, in grams per
denier or tex, required to break the fiber. The tenacity of fiber
differs when it is wet or when it is dry. In general it directly
depends on:
a. length of its polymers
b. degree of polymer orientation
c. strength and types of inter-polymer forces of attraction formed
between polymers
16. 9)Thermal properties
Textile fiber or filament at particular temperature gets softened
and begins to melt. This temperature is a relative measure of the
heat resistance of fiber. It gives the information that at what
temperature the fiber may be safely heat-processed during
finishing, pressed during garment manufacture, hot laundered,
and ironed after dry cleaning.
The softening and melting point temperatures of a fiber are
directly related to the crystallinty of its polymer system, the
length of its polymers, and the type and number of inter-polymer
forces of attraction holding its polymer system together. Due to
more crystalline polymer system, there will be longer polymer
chain and stronger will be its inter-polymer forces of attraction.
Thus more heat or kinetic energy will be required to free the
polymers from each other. This would result in the fiber having a
greater resistance to heat, as well as to softening and melting at a
higher temperature.
17. Amorphous fibers
• more absorbent
• weaker
• less durable
• more easily degraded by
chemicals
• more easily dyed
• more pliable, softer
handling
• plastic, more easily distorted
Crystalline fibers
• less absorbent
• stronger
• more durable
• less easily degraded by
chemicals
• less easily dyed
• less pliable, stiffer handling
• less plastic, resist being
distorted
