The tensile properties of a staple yarn are partly governed by the strength of its constituent fibers and partly by the degree of cohesiveness achieved through the twisting of the fiber assembly. Thus mechanical properties are probably the most important, since they contribute both to processing behavior and to the characteristics of the end product. Textile fibers are available in a very wide range of tensile properties from high tenacity/low extension (such as flax, jute, glass, and fortisan) to low tenacity/high extension (such as wool and acetate fibers). However, a textile fiber must possess a certain minimum strength and adequate extensibility characteristics if it is of any significant use to the textile industry. Some of the end-use properties by the mechanical properties of textile fibers are the durability, low load deformations (wrinkle recovery, drape, etc), resilience, stiffness, abrasion resistance, compressibility, and softness.
MISCELLANEOUS PROPERTIES:
Fiber
density has the property that controls the covering power of a fiber in a
yarn and for that matter in a fabric. In a given weight of fabric the lower the
density, the greater the volume of the fiber present. As a result fabrics made
from yarns of low-density fibers will have a fuller and bulkier appearance than
those made from the higher-density fibers. Because of their low density,
polyethylene and polypropylene float on water, where as cotton and viscose rayon fibers have a
density of about 1.50, will sink in water.
Moisture
absorption can be considered as an asset in so far as the comfort and
warmth characteristic of clothing is concerned. But on the other hand, it may
be a disadvantage and a nuisance when its effect on the changes in dimensional
stability of certain fibers is considered. Moisture absorption changes the
properties of fibers causing it to swell, eventually resulting in changes in fiber
dimensions. Consequently, the size, shape, stiffness, and permeability of yarns
and fabrics are modified. It also affects the mechanical, frictional, and
electrical property (static) of fibers; all these changes influence the
processing behavior and the end-use characteristics.
Normal
changes in temperature conditions do not have any significant effect on
the thermal stability of textiles. But when subjected to high temperatures and
then cooled, the newer synthetic fibers become heat set. By using heat
and pressure the synthetic fibers can be made to acquire textured effects. This
property of the thermoplastic fibers has made them attractive for use in blends
with natural fibers where a reasonable permanence of folds or pleats is
desired. All textile fibers are susceptible to degradation when exposed to very
high temperature conditions. Heating causes decomposition, which result in the
weakening of the products .
During
ordinary wear, textile materials are generally exposed to all kinds of
environmental conditions that can cause their discoloration and degradation.
Prolonged exposure to sunlight, high temperature, moisture and attack
by microorganisms can cause severe damage to the strength of textiles and
thus affect the durability of fabrics and garments. Cotton fiber is prone to
attack by bacteria and organisms when stored in damp conditions. Ultraviolet
rays induce oxidation and cause degradation and damage to the textiles
.Wool fibers are attacked by moths
that lay eggs in the wool material; these eggs hatch-out into grubs that eat wool,
forming holes in the fabric.
Although textile materials are
required to be strong and flexible, it is equally important that they
should be resistant to chemicals. Most natural fibers are inert,
possesses good resistance to mild alkalis and acids, and practically insoluble
in organic solvents, and, of course in water. Very strong acids and alkalis
generally cause most textile fibers to degenerate. It is therefore important to
use inert solvents in dry-cleaning. Other wise materials like acetate, nylon
and rayon will swell or dissolve and lose their useful characteristics.
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