1. RECOMMENDED BOOKS
1. A TEXT BOOK OF ENGINEERING CHEMISTRY-
S. S. DARA.
2. ENGINEERING CHEMISTRY-
M. M. UPPAL
3. INDUSTRIAL CHEMISTRY-
B. K. SHARMA
4. CHEMISTRY OF ENGINEERING MATERIALS-
PROF. DR. MD. MOMINUL HOQUE
22. Nylon is a generic term for synthetic polyamides
capable of forming fibres.
Described by a numbering system which indicates
the number of carbon atoms in the monomer chains.
Aminoacid polymers are designated by a single number,
as Nylon: 6 for poly (w-amino-caproic acid) or polycaprolactum.
Nylons from diamines and dibasic acids are designated
by two numbers:
the first representing the diamine, as Nylon 6:6 for the polymer
of hexamethylene diamine and adipic acid.
NYLON
23. Nylon 6:10 for that of hexamethylene diamine and sebacic acid.
Polyamides of commercial importance are Nylon 6; 6;1,
6:10 and 11(Poly w-amino-undecanoic acid), and their copolymers.
NYLON
24. Nylon 6:6 is prepared by the condensation of adipic acid and
hexamethylene diamine in the absence of air.
HOOC(CH2)4 COOH + H2N (CH2)6 NH2
[NH3 (CH2)6 NH3OOC (CH2)4 COO]n
Nylon 6:6 salt
H-[-N-(CH2)6 N-C-(CH2)4-C-]n –OH + H2O
H H O O
Nylon 6:6 polymer
- H2O Further heating
Adipic acid
Hexamethylenediamine
Polymerization
PREPARATION OF NYLON 6:6
30. Condensation polymerisation
The joining up of two molecules, producing water, is
condensation.
Because giant molecules are made, this is
condensation polymerisation.
Specifically with a diol and a diacid, a polyester is
produced.
35. manufactured fiber consumption
in 1928 manufactured fibers accounted for 5% of
fiber consumption in the U.S…
now
•64% world textile consumption
•83% U.S. textile consumption
consumers continue to value natural fibers, but in
many end uses manufactured fibers are clearly
superior
36. fiber spinning
raw material is:
• natural product—cellulose or protein
• synthetic polymer
dissolved in liquid chemicals and made into a
spinning solution (dope)
all manufactured-fiber spinning processes are based
on these 3 steps:
1. preparing a viscous dope or melt
2. forcing or extruding dope or melt through opening in
spinneret to form a fiber
3. solidifying the fiber by coagulation, evaporation or
cooling
37.
38.
39.
40. fiber modifications
there are 5 general ways that a fiber modification can be made:
1. the size and shape of the spinneret can be changed to produce
fibers of different sizes and shapes
2. the fiber’s molecular structure and crystallinity can be changed to
enhance fiber durability
3. other compounds can be added to the polymer or dope to enhance
fiber performance
4. the spinning process can be modified to alter fiber characteristics
5. in a more complex modification, two polymers can be combined as
separate entities within a single fiber or yarn
41. fiber modifications—spinneret
changing fiber size is a common modification—simplest way is
changing size of spinneret opening
macrofiber: denier greater than 1.0
microfiber: denier less than 1.0
ultrafine fibers: less than 0.3 dpf
nanofibers: fibers with cross sections measuring less than
1,000 nanometers (human hair 80,000 nm)
macro & microfibers currently used in apparel and interior
applications
nanofibers used in protective apparel, safety harnesses &
technical/medical filtration
42. fiber modifications—fiber shape
changing cross-sectional shape is easiest way to alter a fiber’s
mechanical & aesthetic properties—usually by changing shape of
spinneret hole
many shapes possible: flat, trilobal, quadrilobal, pentalobal,
triskelion, cruciform, cloverleaf, Y, T
trilobal widely used in nylon & polyester—beautiful silklike hand,
sheen & color, subtle opacity, soil-hiding capacity, bulk without
weight, wicking, crush resistance, & good textured crimp
multilobal fibers improve hydrophilic, wicking and moisture
management properties
43. fiber modifications—molecular structure
manufacturers can change molecular structure for specific end
uses:
•high-tenacity fibers—modification of polymer to increase
polymerization
•low-piling fibers—slightly reduced molecular weight of polymer
chains
•binder staple—when mixture is heated, bonds regular fibers
together
•low-elongation—changing the balance of tenacity and extension
(useful in blends)
•shape memory fibers—designed to conform to specific shape
when specific stimuli (heat, light, etc…) are activated
44. fiber modifications—additives
delustering:
titanium oxide—a white pigment—is added to spinning solution
before fiber is extruded; particles of pigment absorb
light…weakens fiber
solution dyeing:
addition of colored pigments
or dyes to spinning solution;
provides color permanence;
cost more per pound
than other fibers
45. fiber modifications—additives
whiteners & brighteners:
added to spinning solution to make fibers look whiter & resist
yellowing; reflect more blue light & masks yellowing
cross-dyeable fibers:
incorporates dye-accepting chemicals into molecular structure
antistatic fibers:
fiber is made wettable by adding an antistatic compound to the
fiber-polymer raw material
46. fiber modifications—additives
sunlight-resistant fibers:
nitrogenous compounds added to dope to stabilize reaction
between UV light and fiber or dye; carefully selected for
specific fiber-dye combination
flame-resistant fibers:
produced by changing polymer structure or by adding flame-
retardant compounds to spinning solution
47. fiber modifications—additives
antibacterial fibers:
chemical compounds that kill or discourage growth of
bacteria and other microbes are incorporated in spinning
solution prior to extrusion or during spinning
may require frequent washing to remove microbial debris
and allow additive to work on living microbes
48. fiber modifications—complex
fiber modifications that provide comfort and improve human
performance are important in today’s industry
more efficient materials produce lighter-weight, more
comfortable products
•manage moisture
•wick perspiration away from skin
•provide warmth or insulation
•decrease friction & increase speed
•protect from wind, rain or snow
