textile engineering

1. HAWASSA UNIVERSITY IOT
Department Of Textile and Garment Engineering
Textile finishing seminar:
TO:Mr. Jemal.E By: Group one members
FLAME RETARDANT FINISHES

2. INTRODUCTION
 Textile products can be produced by different
ways namely weaving, knitting and nonwoven
technological production.
 After being produced they need to be treated
with different mechanical and chemical treating
agents.
 These treatments are called finish. Once the
textile product is finished(treated) it become
fit to its purpose(it’s performance gets
improved).
 When it is taken in case of functional fabrics i.e.
produced for the specific purpose the process is
somewhat critical.

3. CONTINUED….
• The mechanical finish improves the appearance
and leaves the performance enhancing to the
chemical one.
• Chemical finishes are those finishes in which
chemicals are used as finishing agents.
Antibacterial finishes
Antistatic finishes
Soil release finishes
Flame retardate and proof finishes

4. CONTINUED…
• In this seminar we will try to clarify one of
formerly listed chemical finishes, flame
retardate and proof finishes.
• The history of flame retardant and proof
finishes takes us back to 400 B.C. and the began
to grow year by year after 17th century.
• These finishes are those finishes which either
reduce spreading of flame in the fabric body or
stops it.
Let’s see how they can do that and why
important it is

5. FLAME RETARDANTS
What are flame retardants?
o Flame retardants are chemicals, which are added
to manufacture materials that inhibit or delay
the spread of a fire.
o The term ‘flame retardant’ describes a function
rather than a chemical class.
o Flame retardants vary in their chemical
structure.

6. CLASSIFICATION OF FLAME RETARDANTS:
Based on their sources:

7. CLASSIFICATION OF FLAME RETARDANTS:
BASEDONRETARDING
EFFECT
Primary retardants
phosphorus and halogen based
Synergistic retardants
haven’t retarding effect alone but
improves retardancy of another
when combined
Adjunctive retardants
that exhibit their activity through
physical effects

8. WHY DO WE USE FLAME RETARDANTS?
• Since they are effective to reduce the
flammability of products and improve safety of
people in the event of fire.
• To delay ignition, slow down the combustion
process, or even make the material self-
extinguishing.
General: for fire protection
 They give us time to escape by reducing flame
spreading in fire events.
Therefore we need fire retardants in times of
exposure to flame.

9. MECHANISMS OF FLAME RETARDANCY
o We need to understand the mechanism of combustion
to know how flame retarding mechanism works.
Let’s get introduced to combustion mechanism:
Combustion:
 combination of oxygen with another compounds to form
heat and usually light.
 Exothermic gas phase free radical reaction having
three elements heat, oxygen and suitable fuel.
 If left unchecked it becomes self-catalyzing
and continues until one of the three elements
is depleted.

10. CURRENT MODEL OF FIBER COMBUSTION

11. COMBUSTION CYCLE

12. VS

13. FIRE RETARDING MECHANISM
• The main principle the flame retardants work with
is breaking combustion cycle.
DIFFERENT WAYS TO BREAKDOWN THE CYCLE
1.To provide heat sink on or in the fiber(inert fillers):
• This system is to use materials that thermally
decompose by strongly endothermic reaction(heat
absorbent reaction).
• These reactions absorb more heat and it takes too
long for pyrolysis to occur.
• Therefore combustion cannot occur.
Using aluminum trihydrate and calcium carbonate as a
filler in the fiber.

14. CONTINUED…
The chemistry:
2.To apply a material that forms an insulating layer
• To use low melting materials as insulation of fiber
then taking longer for pyrolysis to occur.
• Therefor combustion can’t occur.
Use: Boric acid and its hydrated salts
The chemistry:

15. CONTINUED…
3.To influence the pyrolysis
• Phosphorus containing flame retardants produce
phosphoric acid(H3PO4) after being decomposed
with heat (condensed phase mechanism)
• These flame outcomes get cross-linked with
hydroxyl ion in the polymer of fiber.
• This crosslinking inhibits pyrolysis to produce less
flammable products.
The chemistry:

16. CONTINUED…
4. Interfere with the free radical reactions
• Free radicals provide energy for the process to
continue.
• Material at gas phase mechanism have halogen
containing compounds.
• When expose to heat these compounds produce
hydrogen halides that forms less reactive free
radicals then reducing energy provision to
combustion cycle continuation.
•

17. FLAME RETARDANT CHEMISTRY
Chemical reactions can occur both in condensed and gas
phase mechanisms.
Chemical Effect Condensed Phase
Two types of reaction occur in condensed phase
Polymer breakdown:
• Flame retardants accelerate breakdown of polymers
which leads to pronounced polymer flow that reduces the
effect of flame that breaks away.
Charring:
• Retardants cause carbon layer(charring) on polymer
surface then generating double bond on polymer forming
carbonaceous layer.
• The can occur by dehydrating action of retardants.

18. CONTINUED…

19. CHEMICAL EFFECT GAS PHASE
• Retardants degradation products stop the radical
mechanism of the combustion process that takes
place in the gas phase.
• Then the exothermic reaction stops and system
cools down therefore flammable gas supply is
highly reduced.
The radical mechanism:
 The high-reactive radicals HO· and H· can react in
the gas phase with other radicals, such as
halogenated radicals X· resulted from flame
retardant degradation.
 This reaction produces less reactive radicals then
slowing combustion down

20. FLAME RETARDANTS
FOR SOME FIBERS AND BLENDS
Flame Retardants For Cellulose
Cause of thermal degradation of cellulose fibers:
o the formation of the small de-polymerization product
called levoglucosan.
o Levoglucosan and its volatile pyrolysis products are
extremely flammable materials and are the main
contributors to cellulose combustion.
Retardants:
• Those compounds which can reduce formation of
levoglucosan.

21. CONTINUED…
Characteristics of cellulose retardants:
 crosslinking and the single type of esterification
of cellulose polymer chains by phosphoric acid.
Which compounds have to be selected?
 The compounds yielding phosphoric acid at early
stages of pyrolysis are effectives to function as
cellulose retardants.
 Phosphoric acid is added with nitrogen for
synergism( app. 2% P and app. 1% N ).

22. DURABILITY OF RETARDANCY
Applied retardants can be durable or non durable:

23. CONTINUED…
Non durable:
There are many applications where non-durable flame
retardants are adequate.
for example, on drapery and upholstery fabrics that
will not be laundered.
Ammonium sulfate:
Generation non-flammable
gases at the flaming
zone of the burning polymer
as NH3, SO2, N2 and H2O

24. CONTINUED…
Durable:
there are applications where durability is
important, e.g. firefighter suits, children
sleepwear.
Tetrakis (hydroxymethyl) phosphonium Chloride
(THPC)
• prepared from phosphine, formaldehyde and
hydrochloric acid at room temperature.
• It contains 11.5% phosphorous

25. FLAME RETARDANTS FOR WOOL
o Wool is flame retardant in its nature but treating it with
flame retardants can improve its performance.
o It is also a protein fiber but is harder to ignite than silk as
the individual "hair" fibres are shorter than silk and the
weave of the fabrics is generally looser than with silk
Cause of thermal degradation of wool:
• Overheating or exposure to higher ignition source.
Retardants:
o The most common are compounds of Zirconium or zirconium
ions like hexaflouro zirconate or optionally titanate salt.
o The hexafluoro titanium salt is more effective and cheaper,
but a yellow shade is imparted to the treated wool, which is
increased by exposure to light.

26. CONTINUED…
Mechanism:
o Once applied at acidic PH(<3) the heavy metal ion
forms complex with wool fiber as anionic
dyestuff.
o The mechanism is thought to be occur at
condensed phase where zirconium ion enhances
char formation leading to carbon layer on the
fiber surface keeping the root fiber undamaged.

27. CONTINUED….
Treatment durability:
o The finish is durable to dry cleaning and water
washing up to 40°C at pH < 6.
o The PH beyond this can decrease retarding
performance of zirconium ion by zirconium oxide
formation.
Process compatibility with another processes:
o since the process can be carried out at strong
acidic medium we can combine it with leveling
acid dyeing.
o For it can go with insect and shrink resist
finishes it can be done in combination with them.

28. FLAME RETARDANTS
FOR POLYESTER
Cause for polyester thermal degradation:
 The melting ability of polyester when exposed to
ignition source
Retardants:
o Phosphorus and bromine containing compounds
are known to be effective polyester flame
retardants( Gas phase mechanism).

29. CONTINUED…
Three approaches to produce flame retardant
polyester:
• To combine molten state of retardants with
polyester melt and extrude them together via
spinneret or to melt polyester and combine it
with molten retardants
Additives to
polyester melt
• To combine another retardant synthetic
polymer with polyester and extrude them
together
Flame retardant
copolymer
• To improve retardancey after being
produced by Appling surface treatment
with flame retardant compounds to
form film of retardants at the surface
Topical finishes

30. CONTINUED…
Flame-retardant finishes for polyester:
‘Tris’:
o Is name for trisdibromopropylphosphate.
o Can be applied by both padding and exhaustion
processes
o Banned from market for it is found to be
carcinogenic.
Mixture of cyclic phosphate/ phosphonates:
• It is used in a pad–dry–heat set process
Conditions:
Heat set: @190–210ºC
Time: for 0.5–2 min
Add-on: app. 3-4%

31. CONTINUED…
Highly brominated chemicals:
 These chemicals are applied for topical finish
 The most common retardants for this case is
HBCD (hexabromocyclododecane).
 To achieve durable flame retardancy, fabric
padded with ~ 8 % of a dispersion of this water
insoluble material must be heated above 190 °C
to form a film of the flame retardant on the
fiber surface.

32. FLAME-RETARDANTS
FOR FIBER BLENDS
 Providing flame retardancy for blends is not easy task
as we did for single fibers.
 The blends flammability is worse than the
flammability of their components
What happens to the blend when expose to the flame?
o The natural fibers form coal when exposed to flame
and the synthetic one melts. These melted fibers get
held by coal formed by natural fibers and make them
ready to burn.
o Those the flammability of blend exceeds the two
components

33. MECHANISM DEMONSTRATION
 The flame retarding mechanism for blends can be
demonstrated by using limiting oxygen index(LOI)
value.
Let’s get introduced to what LOI is:
o It is content of oxygen in an oxygen/nitrogen
mixture that keeps the sample at the limit of
burning.
o Used as an indicator of flame retadancy of fibers.
o Those fibers having LOI greater than 20 are
thought to be flame resistant than those which
have lower than the value.

34. LOI VALUE FOR COMMON FIBERS
Why made 20?
• It is known that oxygen content of air is 20 %. Then
the oxygen needed to burn material have to be higher
than this. Those fibers having LOI approaching 20
burn easily where as those having more than 20 take
too long to reach at pyrolysis Temperature then burn
less.
Fiber LOI
Ignition
Temperature (°C)
Ease of
Ignition
PVC 35-40 575 Flame resistant
Wool 24-25 590
Will not ignite
readily
Polyester 20-23 485 combustible
Acrylic 18-20 390 combustible
Polypropylene 17-18 350 Burns easily
Cotton 18-21 390 Burns easily

35. CONTINUED…
Now let’s go back to the comparison.
Our fabric is made from cotton/polyester blend yarn
 We can easily see that the blend is less flame
resistant than even the most flammable
component(cotton).
Note: the reverse occurs to some blends. The most
common example is wool/polyester blend (why?)
FIBER LOI
cotton 18.4
polyester 21(average)
The blend 18

36. HOW TO MAKE THE BLEND
FLAME RESISTANT?
o The main strategy is to add high level of flame
retardants.
For cotton/polyester blend:
• decabromodiphenyl oxide (DBDPO) in combination
with antimony trioxide is the most common.
Drawbacks:
• Need for higher add-on up to 37% with binder and
softeners.
• The application can affect color and hand of finished
product.
• Higher chemical cost.
Note: Despite the above fact the strategy is being
commercialized still today.

37. NOVEL APPROACH TO FLAME RETARDANTS
INTUMESCENT
o This is the generation of expanded, foamed char
formed by heat and special additives.
The additives:
 char formers (for example starch)
 catalysts that yield inorganic acids at about 150 °C
 generators that provide non-flammable gases for the
foam and binders for fixation to the fabric
The process:
o The system provides a foamed insulation layer on the
fabric surface as in cotton, wool and Basofil fibers.
o Provides all flame retarding requirements such as
preventing, retarding further flaming and flame
barrier formation

38. EVALUATION OF FLAME RETARDANTS
o Is to determine how much effective flame
retardant finishes are.
Factors affecting flame retardancy
o Types of fiber
o Fabric weight and construction
o Methods of ignition
o Presence or absence of retardants
o Extent of material and heat exchange

39. SOME OF THE MOST COMMON TESTS:
R.No Test methods Procedures(comments)
1 16 CFR 1610 Is used for general apparel and the fabric is
held at 45 0 to the flame for a second
2 16 CFR 1615/1616 For children’s sleepwear Fabric held vertical to
flame for3 s.
3 NFPA 1971 Fabric held vertical to flame for 12 s. For
protective clothing.
4 NFPA 701 Fabric held vertical to flame for 45 s to 2 min.
For drapery.
5 ASTM-2863
Limited oxygen index(LOI)
Fabric is held vertical in atmosphere of different
oxygen/ index (LOI) nitrogen ratios and ignited
from top. Determines minimum oxygen level to
support combustion.

40. PROBLEMS WITH FLAME RETARDANTS
Side effects to fabric physical properties
o Flame retardant finishes were found to have an
impact on physical properties of the material
specially when added in higher amount.
o Some of the problems they may cause harsh hand,
loss of tensile strength and color effects (fabric
yellowing and dye shade changes) in case of
durable finishes for cotton.
o The combination with other finishes, such as
softeners, easy-care and repellent finishes, must
be carefully tested

41. CONTINUED…
Toxicity of some of flame retardants:
o most common in halogen and metal ion based
retardants
o phosphorous, antimony and zirconium compounds
in the waste water.
o Formaldehyde release during curing of the
permanent flame retardant finishes of cellulose
and free formaldehyde of finished fabrics
(storage, transport).

42. RETARDANCY VS. PROOF
Wikipedia definition:
Flame retardants:
o are those products (materials) designed to burn
slowly.
Fireproof (resistant):
o is rendering something resistant to fire, or
incombustible; or material for use in making
anything fire-proof. It is a passive fire
protection measure.

43. FROM NON-PERMANENT TO PERMANENT
Permanents:
Applies two approaches here
1-To bind molecules chemically but using one of its OH ion
2-By polymerization of the product with itself forming layer in and around
the fiber
IN BOTH cases phosphorus derivatives are used
Non permanents:
In this case salts dissolved in water are applied to the
fabric by padding and dried. The retardacy is lost when the
fabric comes in contact with water

44. APPLICATION IN PERMANENTS
o Padding in a bath containing the flame-retardant
product. It is a pre-condensate of THPC (TETRAKIS
HYDROXYMETHYL PHOSPHONIUM CHLORIDE).
o Passage into a machine filled with gaseous ammonia
allowing a poly-condensation chemical reaction to take
place. The ammonia group serves as a link between the
different molecules and Drying
o Washing and oxidation to remove unbound products and
to stabilize phosphorus at a five-fold bond
o Finally drying

45. PROOF MATERIAL WITH RETAINED
MECHANICAL PROPERTIES

46. APPLICATION OF FLAME RETARDANTS:
Some of them:
• For home insulation
• In upholstery furniture’s containing poly-ethane
foam
• Plastic casing of electronics
• In carpet padding
• In some baby products like diaper changing pad.

47. THE NEW APPROACH TO FLAME RETARDANTS
• States it is not right or enough to decide
flammability of textile martial with its
LOI(ability to ignite) value only rather HRC(level
of heat release in combustion) have to be
considered too.
• Those having low LOI may have low HRC(?)

48. CONCLUSION:
• Fire retarding finishes impart fire spread
retarding or resisting capacity to the product.
• We can apply different retarding chemicals to
impart the property depending on an end use.
• These chemicals can have an effect on health
and physical properties of fabric.
• Blends retarding performance is lower than their
components
• The performance imparted can be temporary or
permanent.
• Fire retardant materials have many applications
in our daily activities.

49. REFERENCES:
o Wikipedia
o Chemical finishing of textiles by W. D. Schindler
and P. J. Hauser page 98-116
o https://www.youtube.com/watch?v=4_EUl70oSwc
(video)
o NPTEL/textile finishing/functional fabrics

50. PEER-I MEMBERS
R.NO Name ID
1 Melkamu Kenito TECH/0750/09
2 Meron Tebikew TECH//09
3 Azeb Mekonin TECH//09
4 Abdulkerim Nesru TECH//09
5 Selamawit Asalfew TECH/ /09

51. THIS IS ALL WE HAVE!
Thank you!