Crease:
This is a fabric defect evidenced by a break line or mark or fold in a fabric generally caused by a sharp fold. Crease appears when the fabric is distorted in such a manner that part of it is stretched beyond its elastic recovery.
During creasing the upper surface of fabric goes on extension and lower surface goes on compression.
Crease Resistance :
The resistance to creasing of textile material during use is known as crease resistance.
Amongst the textile materials the decreasing order of crease resistance is wool, silk, acetate rayon, viscose, rayon, cuprammonium rayon, cotton, flax etc.
Crease recovery :
It is the property of a textile material by which it can return to its former shape after being creased. The measure of crease resistance is specified quantitatively in terms of crease recovery angle. The crease recovery of a fabric can be increased by resin treatment.
Construction/machine description :
The instrument consists of a circular dial which carries the clamp for holding the specimen.
Directly under the center of the dial is a knife edge and an index line for measuring the recovery angle.
The scale of the instrument is engraved on the dial.
Working Procedure :
A specimen is cut from the fabrics with a template 2 inch long by 1 inch wide.
It is carefully creased by folding in half placing it between two glass plates and adding a 2 kg weight.
After 1 min the weight is removed and the specimen transferred to the fabrics clamp on the instrument and allowed to recover from crease.
As it recovers, the dial of the instrument is rotated to keep the free edge of the specimen in line with the knife edge.
At the end of the time period allowed for recovery, usually 1 min the recovery angle in degrees is read on the engraved scale.
Warp and weft way recovery are reported separately to the nearest degree from the mean values of ten tests in each direction
Considering points while testing :
The specimen should be conditioned and tested in a standard testing atmosphere.
Random sample should be taken.
Selvedge, piece ends, creased or folded regions should be avoided.
