Slide 1

Report
Yarns
Now that you have the
fibers what do you do
next?
Spinning
Spinning
• Different connotation for natural &
manufactured fibers
– Natural: making long yarn from short fibers
– Manufactured: making fibers and yarn
simultaneously
• Sometimes manufactured fibers are “chopped” up
into short fibers and then treated as if they were
natural fibers
Manufactured Fibers - Spinning
Spinneret
Spinning
Dope
Spinne re t
Polymer Reservoir
Take -up
Take-up
Pump
Coagulating Bath
Wet Spinning
Spinning
Dope
Mo lten
Poly mer
Pump
Pu mp
Spinne re t
Sp in n er et
Warm air
Coo l air
Take -up
Dry Spinning
Tak e- u p
Me lt S pin nin g
Manufactured Fibers - Summary
Summary of Major Fiber Spinning Methods
DRY
MELT
WET
Polymer before spinning
solution
solution
molten
Spinning Environment
solution
warm air
cool air
rayon
acetate, acrylic
polyester, nylon
Example
Natural Fibers - Twisting
• Fibers are put in a parallel bundle and the bundle is
drawn down and twisted to form a yarn
• 2 competing effects
– Cohesion: friction as fibers are pressed into one another
produces strength
– Obliquity: fibers can carry the most load along their axis; twisting
causes the fiber axis and yarn axis to be different
Yarn
Strength
cohesion
yarn strength
obliquity
Twist
Twist Direction
S
Z
S - twist
Z - twist
• No effect on yarn strength
• Can affect other properties
– Untwisting in larger structures
– Fabric thickness
Complex Yarn Structures
•
•
Very large textile structures can be
built up by twisting together other
structures. For example, two or
more single yarns can be twisted
together to form a plied yarn; two
or more plied yarns twisted
together form a cord; two or more
cords form a cable ad infinitum.
The twist in each of the parts is
alternated so, for example, if the
twist in the single yarn is 'Z', the
plied yarn will have 'S', the cord
'Z'; the cable 'S' …
The twist is alternated to help
prevent the larger structure from
untwisting.
Yarn Numbering Systems
• Direct (ND)
– Our “old friends” from
linear density
– As yarn gets larger its
yarn number increases
– Usually used with
manufactured yarns
ND =
WS
L
ND
S
denier (Nd)
9000 m/g
tex (Nt)
1000 m/g
decitex/dtex (Ndt)
10000 m/g
Yarn Numbering Systems
• Indirect (NI)
– As yarn gets larger its
yarn number
decreases
– Usually used with
twisted yarns
NI =
L
WS
NI
S
English cotton
(Ne)
840 yd/lb
worsted (Nw)
560 yd/lb
woolen run (Nwr)
1600 yd/lb

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