YARN
CRIMP IN FABRIC
Yarn Crimp
When warp and weft interlace in
fabric, they follow a curved way. Crimp in a fabric is the measure of this
waviness. Crimp of yarn is measured in crimp%.
Crimp% is defined as the mean
difference between the straightened thread length and curved thread length
while in the cloth and is expressed as percentage.
Crimp%= Uncrimped length-Crimped
length x100
Crimped length
Crimp Amplitude
This refers to the extent to which
the threads are deflected from the central plane of the cloth.
Crimp
Interchange
When a fabric is subjected to
uniaxial stress, the crimp in the direction of loading is gradually reduced and
the crimp in the transverse threads increases. This is called crimp
interchange. Actually the reduction of crimp in warp yarns is equal to the
increment of crimp in weft yarns. As a result, total crimp of yarn (Both warp
and weft) in fabric remains constant.
That is, Cwarp + Cweft
= constant; where, Cwarp= Warp crimp and Cweft= Weft
crimp
Crimp Ratio
The ratio of yarn length and cloth
length is termed as crimp ratio.
So, crimp ratio= yarn length/cloth
length
Factors
Affecting Crimp% of Yarn in the Cloth
v EPI- Higher the EPI,
higher will be the weft crimp%
v PPI- Higher the PPI,
higher will be the warp crimp%
v Warp linear density-
Higher the coarseness of warp, higher will be the weft crimp%
v Weft linear density-
Higher the coarseness of weft, higher will be the warp crimp%
v Yarn tension- Higher the
warp tension, higher will be the weft crimp%
v Weave structure- Higher
the interlacement no., higher will be the crimp%
v Yarn twist- Higher the
twist in warp than weft, lower will be the weft crimp%
v Yarn extensibility-
Higher the warp extensibility, lower will be the weft crimp%
v Calendering finish-
Higher calendering results lower crimp% of yarn
