Heat setting is a thermal treatment process used to impart properties like shape retention, crease resistance, and elasticity to fibers. It involves heating fibers above their glass transition temperature to allow molecular chains to relax into a stress-free configuration, then forming new intermolecular bonds during cooling to freeze the fibers in their relaxed state. The objectives of heat setting are to homogenize fiber structure, eliminate internal tensions, and reduce shrinkage, improving dimensional stability and reducing creasing and curling. It can be done temporarily, semi-permanently, or permanently depending on the heat exposure and its effects on the fiber morphology. Common fibers like polyester, nylon and acrylic each have their own optimal heat setting temperature ranges and durations

1. INTRODUCTION TO HEAT SETTING
 Heat setting is carried out to bring the material to it’s thermal
equilibrium the material wouldn’t changes it’s morphology
it’s kept at that temperature for a long.
 Heat setting is also known as ANNEALING.
 The degree of set, a term often used to describe the extent
of heat setting is the measure of how close the material has
moved to a thermal equilibrium. A 100% set material is
considered to be at its thermal equilibrium at a given
temperature.

2. Mechanism of Heat Setting
• The setting temperature used is
above Tg. In heat setting, inter-chain
bonds, such as hydrogen and dipole
bonds, break. This allows the
molecular chains to move and adopt
new, stress-free positions. New
intermolecular bonds then form with
the fabric in a relaxed condition at
the setting temperature. After
cooling, the polymer molecules in
the filaments become frozen in
place. The new bonds are stable up
to the heat setting temperature. The
reorganized internal polymer
structure, and the material’s
dimensions, will be stable.

4. Objectives
The objectives of heat setting processes include
structure homogenization and the elimination of
internal tensions within the fibre resulting in reduced
shrinkage, improved dimensional stability, reduced
creasing propensity and reduced edge-curl in woven
and knitted fabrics. To this extent, the process may be
better described as thermal relaxation. Heat setting
changes not only the mechanical, but also the dyeing
properties of man-made fibres. The principle is based
on heating the fibre within a fibre-specific temperature
range which is limited at the upper end by the melting
point (softening range) and the respective glass transition
temperature (necessary to break the secondary
bonds) at the lower end.

5. WHY HEAT SETTING IS DONE ….?
Heat setting is a heat treatment by which shape retention,
crease resistance & elasticity are imparted to the fibres.
It also brings changes in strength, stretchability, softness,
dyeability & sometimes on the colour of the material.
All these changes are connected with the structural &
chemical modifications occurring in the fibres.

6. TYPES OF HEAT SETTING
Heat setting
Temporary
heat setting
Semi-
permanent
heat setting
Permanent
heat setting

7. TEMPORARYHEAT SETTING-
This type of heat
setting is destroyed by
regular use of material.
For ex:- A steam
pressed cotton textiles.

8. SEMI-PERMANENTHEATSETTING-
In this type of heat
setting material is raised
above their glass
transition temperature &
then set into a new form.
This type of set is
maintain in normal use
of material however the
setting is lost when the
material is subjected to
severe condition of use.
For ex:- hot washing or
steaming of material above
Tg.

9. PERMANENT HEAT SETTING
• This type of heat
setting involves
change of internal
morphology of the
material in such a
way that it would not
revers till the
material is destroyed
by taking it above it’s
melting point.

10. Heat Set Temperature of some Fibres
Fibre Min T. °C Max. T. °C Time (in seconds)
Polyester (PE) 170 210 15-50
Polyamide PA 6.6 170 210 15-40
Polyamide PA 6 160 180 15-40
Triacetate 160 180 15-40
Acrylic (PAC) 160 180-200 15-40
Elastomers 170 180-200 15-40

11. Stages of heat setting
Heat setting can be carried out at three different stages:
• In grey condition
• After scouring
• After dyeing

12. Heat setting at grey stage
• If heat setting is carried out in loom state, mineral oils and
non-ionic emulsifiers can modify the fiber.
• Structure and rubbing and perspiration fastness may be
reduced due to the solubility of disperse dye in the coning oil.
• However, grey heat setting is useful in warp knitting industry
as in that material carry less amount of lubricants.
• Yellow color due to heat setting can be removed by bleaching.
• Fabric is less sensitive to crease formation in next processes.

13. Heat setting after scouring
Heat setting is done after scouring if it is suspected that:
• goods will shrink .
• Cloth has developed stretch or other properties after scouring.

14. Heat setting after dyeing
These fabric shows considerable resistance to stripping compared
with dyeing on unset fabric.
Disadvantage of this are:
• Yellow color developed can not b removed.
• Handle of cloth may get altered.
• Risk of color to get fade.

15. Mechanism used for Heat Setting
Machines used: Stenters.
 Fluctuating temperatures inside the stenter cause a consistent variation of
crystallinity in the fibre structure, which leads to different affinity for dyes.
 The moisture in the fibre produces soft hand, but variable moisture
percentages in the different fabric sections create the above mentioned defect
(variable crystallinity).
 Too low temperatures do not allow a good setting while too high
temperatures and too long
 setting times cause yellowing (PA and elastic fibres), stiff hand (acrylics), and
loss of elasticity (elastic fibres).

16. References
• Book- VB Gupta & VK Kothari.
• http://www.slideshare.net/sheshir/heat-
setting?qid=51840e8d-4fdc-4c2f-a012-
753c10478363&v=&b=&from_search=1
• file:///D:/Forms,%20Results%20&%20docs/SEMINAR/NPTEL
%20__%20Textile%20Engineering%20-
%20Textile%20chemical%20Processing_%20Theory%20and
%20practice%20of%20Preparatory%20Processes.html
• Encyclopedia of textile finishing.

17. ThankYou!