3. What is the Dimensional Stability of
Fabrics?
The dimensional stability of fabric refers to the change of
fabric size when it is used or reprocessed due to the
properties of a material and the potential thermal
contraction force in the process of processing. The fabric
with good dimensional stability is worn and washed for
many times, the original pleating and shape are unchanged,
and the dimensions don’t shrink or elongated, which don’t
affect the user experience.
The fabric with poor dimensional stability is usually shown
as shrinkage, such as shrinkage in sewing, ironing, washing
and so on. Among them, the wash shrink is the problem that
consumer pays close attention to very much.
4. TYPES OF DIMENSIONAL CHANGE
The types of dimensional change that can occur
when wool fabrics are treated during processing, or
in use, can be placed into five general groups:
(i) relaxation
(ii) consolidation
(iii) swelling
(iv) felting
(v) hygral expansion due to changes in
moisture content.
5. Relaxation shrinkage
Relaxation shrinkage occurs when the stresses or
strains imposed during the processing of the textile
materials are relaxed in water (or water plus soap or
detergent), without agitation.
Relaxation shrinkage is what might be called the first
stage of shrinkage. This form of shrinkage is common
to all fibre types and fabric constructions and is non-
reversible. Special finishing processes relieve these
strains, e.g. tensionless drying of knitted goods and the
crabbing process applied to worsted fabrics.
6. Consolidation shrinkage
The relaxation of residual strains in a fabric is
frequently opposed by frictional constraints within the
fabric brought about by fibre-fibre and yarn-yarn
contacts. Further shrinkage; called consolidation
shrinkage; can be brought about by gentle agitation in
addition to simple soaking. This process is non-
reversible.
In the case of knitted fabrics, consolidation shrinkage
can occur with each washing. A bending of loops tends
to occur due to the difference in twist at opposite sides
of the loops. The strains are released upon washing
and shrinkage occurs.
7. Swelling shrinkage
The longitudinal swelling is negligible while the
transverse swelling is appreciable. The transverse
swelling can lead to dimensional changes known as
swelling shrinkage. The problem is common to all
hydrophilic fibres but is reversible.
8. Felting shrinkage
When untreated wool in any form is treated in water with
soap/detergent it will swell and consolidate. If, however,
some mechanical action is applied, particularly in an acid
medium, the fibres can migrate and mat together tending to
give, in the end, a solid mass of fibres. The result is an
irreversible shrinkage called felting shrinkage.
Wool fibres, like most animal fibres, have a series of
overlapping scales on the fibre surface. The scales point to
the tip direction of the fibres, and the interlocking action of
the scales, sometimes described as a ratchet-like action,
causes the fibres to move preferentially in the direction of
the root of the fibre.
9. Fabric Finishing
The objective of wool fabric finishing is to develop the
desired properties in woollen and worsted fabrics that
meet the specified end use requirements of consumers.
Finishing is a sequence of dry and wet processes that is
carried out in a logical order. There are four main
objectives to be achieved from the finishing of wool
fabrics.
10. The removal, by scouring, of contaminants from the fabric.
These contaminants may include lubricants and antistatic
agents employed in yarn and fabric production, warp sizes and
lubricants, machine oil stains, etc. In some cases the wool
fabric may also contain vegetable matter (VM), in which case
the process known as carbonising may be used to remove the
VM.
The development of the required handle, softness, fullness,
drape, etc.
The control of the dimensional stability of the fabric, e.g.
relaxation shrinkage, felting shrinkage, and hygral expansion .
The application of functional finishes, e.g. antistatic agents,
flame-retardants, waterproofing agents, soil repellents, etc.
Fabric Finishing
12. Wet finishing
The objectives of wet finishing of wool fabrics are firstly to
remove contaminants from the wool by scouring and, if
necessary, by carbonising. The latent stresses and strains the
fabrics must then be relaxed, and the fabric set, in a process
known as crabbing. Special qualities can then be developed
in the wool fabrics by processes known as milling, shrink
proofing, bleaching and dyeing. These so called wet finishing
processes are grouped together, the aim being to minimise
water consumption and to dry the fabric only once.
The so called dry finishing processes for wool fabrics follow
on after hydroextraction and scutching, beginning with
drying. One of the objectives in wool fabric finishing is to dry
the fabric only once, to minimise energy usage.
14. Inspection
Purpose of fabric inspection:
Fabric inspection, mapping or marking defects is
important prior to spreading and cutting because:
1. Spreading can be done more quickly because the
spreader is not also inspecting the fabric.
2. A cutter's productivity will increase because the
defects are already marked.
3. The patterns are cut around the defects so as not to
include them in the finished garment.
15. Fabric Inspection Systems
There are various fabric inspection systems:
1. 10-Point System.
2. Graniteville "78" system.
3. Dallas system.
4. 4- Point system.
18. Spreading or Laying
Spreading is the process of unwinding large rolls of fabric into
long, wide tables in preparation for cutting each piece of a
garment. The number of layers of fabric is dictated by the
number of garments desired and the fabric thickness. Spreading
can be done by hand or machine. Depending upon the fabric and
cutting technology, up to 200 layers of fabric may be cut at one
time. Fabrics that are more difficult to handle are generally cut in
thinner stacks.
Spreading and cutting is smooth laying out of fabric in
superimposed layers or piles of specified length. The cutting
marker is laid on the topmost layer. The maximum cutting width
is the usable fabric width minus selvedge or needle marks caused
by stencil marks. Fabric utilization is the amount of fabric
actually utilized in the marker as the percentage of the total
fabric area.
19. Types of Lay Plan
Half Garment Lay includes only half of the garment
pieces, for example, one side left or right. Generally
used for tubular fabrics.
Whole Garment Lay includes garment pieces, left
and right sides. Generally used for Open width fabrics.
Single Size Lay is used using all garment pieces of
one single size. Disadvantageous as the consumption
of fabric is higher.
20. Types of Lay
Single Ply is a single layer of fabric generally to
make samples
A multiple Ply is a number of fabric layers stacked
on one top of other
Stepped Lay is multiple lays in which groups of
layers have different lengths generally used for
getting best utilization and consumption of fabric.
21. Forms of Spreading
One Way Cutting is when the fabric is laid the same
way up with grain or print pattern running in the same
direction. The fabric has to be cut at the end of each ply.
The fact to Face Cutting is when the plies are laid in
pairs face to face. The grain or pattern runs in the same
direction.
Two Way Cutting is when plies are laid continuously
from left to right and right to left without cutting at the
end. Most Efficient method of spreading. Cannot be used
with grain restrictions or one-directional printed fabric.
