Fiber
Fiber is a natural or synthetic string used as a
component of composite materials, or, when matted
into sheets, used to make products such as paper,
papyrus, or felt.
Synthetic fibers can often be produced very cheaply
and in large amounts compared to natural fibers, but
for clothing natural fibers can give some benefits,
such as comfort, over their synthetic counterparts.
Natural Fibers
Natural fibers include those produced by plants,
animals, and geological processes and can be
classified according to their origin:
Vegetable fibers are generally based on
arrangements of cellulose, often with lignin:
examples
include cotton, hemp, jute, flax, ramie,sisal, bag
asse, and banana. Plant fibers are employed in
the manufacture of paper and textile (cloth),
and dietary fiber is an important component of
human nutrition.
Wood fiber, distinguished from vegetable
fiber, is from tree sources. Forms
include ground wood, lacebark, thermo
mechanical pulp (TMP), and bleached or
unbleached kraft or sulfite pulps. Kraft and
sulfite (also called sulphite) refer to the type of
pulping process used to remove the lignin
bonding the original wood structure, thus
freeing the fibers for use in paper
and engineered wood products such
as fiberboard.
Animal fibers consist largely of particular
proteins. Instances are silkworm silk, spider
silk, sinew, catgut, wool, sea silk and hair such
as cashmere, mohair and angora, fur such as
sheepskin, rabbit, mink, fox, beaver, etc.
Mineral fibers include the asbestos group.
Asbestos is the only naturally occurring
long mineral fiber. Six minerals have been
classified as "asbestos" including chrysotile of
the serpentine class and those belonging to
the amphibole class: amosite, crocidolite, trem
olite, anthophyllite and actinolite. Short, fiber-
like minerals
include wollastonite and palygorskite.
Biological fibers also known as fibrous
proteins or protein filaments consist largely of
biologically relevant and biologically very
important proteins, mutations or other genetic
defects can lead to severe diseases. Instances
are collagen family of proteins, tendon, muscle
proteins like actin, cell proteins
like microtubules and many others, spider
silk,sinew and hair etc.
Man-made Fibers
Man-made fibers or chemical fibers are fibers
whose chemical composition, structure, and
properties are significantly modified during the
manufacturing process. Man-made fibers consist
of regenerated fibers and synthetic fibers.
Semi-synthetic fibers
Semi-synthetic fibers are made from raw
materials with naturally long-chain polymer
structure and are only modified and partially
degraded by chemical processes, in contrast to
completely synthetic fibers such
as nylon (polyamide) or dacron (polyester),
which the chemist synthesizes from low-
molecular weight compounds by polymerization
(chain-building) reactions. The earliest semi-
synthetic fiber is the cellulose regenerated
fiber, rayon. Most semi-synthetic fibers are
cellulose regenerated fibers.
Cellulose regenerated fibers
Cellulose fibers are a subset of man-made fibers,
regenerated from natural cellulose. The cellulose
comes from various sources: rayon from tree
wood fiber, Modal from beech trees, bamboo
fiber from bamboo, seacell from seaweed, etc. In
the production of these fibers, the cellulose is
reduced to a fairly pure form as a viscous mass
and formed into fibers by extrusion through
spinnerets. Therefore, the manufacturing process
leaves few characteristics distinctive of the natural
source material in the finished product.
Some examples are:
rayon
bamboo fiber
Lyocell, a brand of rayon
Modal, using beech trees as input
diacetate fiber
triacetate fiber.
Historically, cellulose diacetate and -
triacetate were classified under the term
rayon, but are now considered distinct
materials.
Synthetic fibers
Synthetic come entirely from synthetic materials
such as petrochemicals, unlike those man-made
fibers derived from such natural substances as
cellulose or protein.
Fiber classification in reinforced plastics falls into
two classes: (i) short fibers, also known as
discontinuous fibers, with a general aspect ratio
(defined as the ratio of fiber length to diameter)
between 20 to 60, and (ii) long fibers, also known
as continuous fibers; the general aspect ratio is
between 200 to 500.
Metallic fibers
Metallic fibers can be drawn from ductile metals
such as copper, gold or silver and extruded or
deposited from more brittle ones, such as nickel,
aluminum or iron. See alsoStainless steel fibers.
Carbon fiber
Carbon fibers are often based on oxydized and
via pyrolysis carbonized polymers like PAN, but
the end product is almost pure carbon.
Silicon carbide fiber
Silicon carbide fibers, where the basic polymers
are not hydrocarbons but polymers, where about
50% of the carbon atoms are replaced by silicon
atoms, so-called poly-carbo-silanes. The pyrolysis
yields an amorphous silicon carbide, including
mostly other elements like oxygen, titanium, or
aluminium, but with mechanical properties very
similar to those of carbon fibers.
Fiberglass
Fiberglass, made from specific glass, and optical
fiber, made from purified natural quartz, are also
man-made fibers that come from natural raw
materials, silica fiber, made fromsodium
silicate (water glass) and basalt fiber made from
melted basalt.
Mineral fibers
Mineral fibers can be particularly strong because
they are formed with a low number of surface
defects, asbestos is a common one.[8]
Polymer fibers
Polymer fibers are a subset of man-made
fibers, which are based on synthetic chemicals
(often from petrochemical sources) rather than
arising from natural materials by a purely
physical process. These fibers are made from:
polyamide nylon
PET or PBT polyester
phenol-formaldehyde (PF)
polyvinyl chloride fiber (PVC) vinyon
polyolefins (PP and PE) olefin fiber
acrylic polyesters, pure polyester PAN fibers
are used to make carbon fiber by roasting
them in a low oxygen environment.
Traditional acrylic fiber is used more often as
a synthetic replacement for wool. Carbon
fibers and PF fibers are noted as two resin-
based fibers that are not thermoplastic, most
others can be melted.
Aromatic polyamids (aramids) such
as Twaron, Kevlar and Nomex thermally
degrade at high temperatures and do not
melt. These fibers have strong bonding
between polymer chains
Polyethylene (PE), eventually with extremely
long chains / HMPE (e.g. Dyneema or
Spectra).
Elastomers can even be used,
e.g. spandex although urethane fibers are
starting to replace spandex technology.
polyurethane fiber
Elastolefin
Coextruded fibers have two distinct polymers
forming the fiber, usually as a core-sheath or
side-by-side. Coated fibers exist such as nickel-
coated to provide static elimination, silver-
coated to provide anti-bacterial properties and
aluminum-coated to provide RF deflection
for radar chaff. Radar chaff is actually a spool
of continuous glass tow that has been
aluminum coated. An aircraft-mounted high
speed cutter chops it up as it spews from a
moving aircraft to confuse radar signals.
microfibres
Microfibers in textiles refer to sub-denier fiber
(such as polyester drawn to 0.5
denier). Denier and Dtex are two measurements
of fiber yield based on weight and length. If the
fiber density is known, you also have a fiber
diameter, otherwise it is simpler to measure
diameters in micrometers. Microfibers in
technical fibers refer to ultra-fine fibers (glass or
meltblown thermoplastics) often used in
filtration. Newer fiber designs include extruding
fiber that splits into multiple finer fibers. Most
synthetic fibers are round in cross-section, but
special designs can be hollow, oval, star-shaped
or trilobal. The latter design provides more
optically reflective properties. Synthetic textile
fibers are often crimped to provide bulk in a
woven, non-woven or knitted structure. Fiber
surfaces can also be dull or bright. Dull surfaces
reflect more light while bright tends to transmit
light and make the fiber more transparent.
Very short and/or irregular fibers have been
called fibrils. Natural cellulose, such as cotton or
bleached kraft, show smaller fibrils jutting out
and away from the main fiber structure.
Tensile Strength
Of Fibers
Depending upon the sources, the various types of
fibers can be classified into the following main three
categories:
Animal Fibers
Vegetable Fibers
Synthetic fibers
Besides their chemical
composition and properties,
most important property of these fibers is their
tensile strength, meaning the extent to which a fiber
can be stretched without
breaking and it is measured in
terms of minimum weight
required to break the fiber. To
determine the tensile strength
of nay fiber, it is tied to a hook at one end and
weights are slowly added to the other end until the
fiber breaks.
Since peptide bonds are more
easily hydrolyzed by bases
than by acids, therefore wool
and silk are affected by bases
and not by acids.
It is because of this reason that wool and silk threads
breakup into fragments and ultimately dissolves in
alkalines.
In other words, alkalines
decrease the tensile
strength of animal fibers
(wool and silk), vegetable
fibers (cotton and linen),
on the other hand, consist
of long polysaccharide chains in which the various
glucose units are joined by
ethers linkage. Since ethers are
hydrolyzed by acids and not by
bases,
therefore
vegetable fibers are affected by
acids but not by bases. In
other words, acids decrease
the tensile strength of
vegetable fibers. In contrast,
synthetic fibers such as nylon and polyester
practically remain unaffected by both acids and
bases.Synthetic fibersowe some of their chemical
resistance to their more 'crystalline' structure, i.e.,
there is greater regularity in the molecular structure,
and this regularity reduces the ability of bases or
acids to approach the amide bonds to initiate a
hydrolytic reaction.
