Flame retardants are added to cotton and other materials to slow or prevent the spread of fire. They work by interfering with the combustion process in various ways such as cooling, forming a protective layer, diluting flammable gases, or interrupting chemical reactions. Common flame retardants include brominated, chlorinated, phosphorus-containing, and nitrogen-containing chemicals. They can be added during production or in a finishing process. Treating cotton with a solution of THPC flame retardant followed by drying and curing can help fireproof the material for uses such as firefighting gear or theater curtains.

1. FLAME RETARDANT FINISHING
ON COTTON MATERIALS

2. INTRODUCTION
• The term flame retardants subsumes a
diverse group of chemicals which are added to
manufactured materials, such as plastics and
textiles, and surface finishes and coatings.
• Flame retardants are activated by the
presence of an ignition source and are
intended to prevent or slow the further
development of ignition by a variety of
different physical and chemical methods.

3. INTRODUCTION
• They may be added as a copolymer during the
polymerisation process, or later added to the
polymer at a moulding or extrusion process or
(particularly for textiles) applied as a topical
finish.
• Mineral flame retardants are typically additive
while organohalogen and organophosphorus
compounds can be either reactive or additive.

4. Burning Mechanism

5. Burning of Textiles

9. Burning of Cellulose

10. LOI (Limiting Oxygen Index)
• The limiting oxygen index (LOI) is the
minimum concentration of oxygen , expressed
as a percentage, that will support combustion
of a polymer .
• It is measured by passing a mixture of oxygen
and nitrogen over a burning specimen, and
reducing the oxygen level until a critical level
is reached

11. LOI Value for different fibre and
polymer

12. Function of a Flame Retardant
• Flame retardants are chemicals are applied to
fabrics to inhibit or suppress the combustion
process.
• They interfere with combustion at various stages
of the process e.g. during heating,
decomposition, ignition of flame spread.
• Fire is gas phase reaction. For a substance to
burn, it must become a gas. As with any solid, a
textile fabric exposed to a heat source
experiences a temperature rise.

13. Function of a Flame Retardant
• If the temperature of the source (either radiative or
gas flame) is high enough and the net rate of heat
transfer to the fabric is great, pyrolytic decomposition
of the fiber substrate will occur.
• The products of this decomposition include
combustible gases, non combustible gases and
carbonaceous char.
• The combustible gases mix with the ambient air and its
oxygen.
• The mixture ignites, yielding a flame, when its
composition and temperature are favorable.
• Part of the heat generated within the flame is
transferred to the fabric to sustain the burning process
and part is lost to the surroundings.

14. Mechanism of Flame Retardancy

15. Mechanism of Flame Retardancy
• Combustion- Is an exothermic process requiring three
components: heat, oxygen, fuel that is suitable.
• Pyrolysis (TP)temperature, to- At this temperature, the
fibre undergoes irreversible chemical changes,
producing
• Non-flammable gases (carbon dioxide, water vapour
and the higher oxides of nitrogen and sulfur)
• carbonaceous char, tars (liquid condensates) and,
flammable gases (carbon monoxide, hydrogen and
many oxidisable organic molecules).

16. The combustion temperature, TC-
At this point, the flammable gases combine with oxygen in
the process called combustion. which is a series of gas
phase free radical reactions.
These reactions are highly exothermic and produce large
amounts of heat and light.

17. Mechanism of Flame Retardancy
Flame retardant systems for synthetic or natural polymers can act physically and/or
chemically by interfering at particular stages of burning
• By cooling Endothermic processes triggered by the flame retardants cool the
substrate.
• By forming a protective layer: The heat transfer is impeded, fewer pyrolysis gases
are evolved, and the oxygen is excluded.
• By dilution.: Substances, which evolve inert gases on decomposition, dilute the fuel
in the solid and gaseous phases. The concentrations of combustible gases fall under
the ignition limit.
• Reaction in the gas phase: The free radical mechanism of combustion processes
which takes place in the gas phase could be interrupted by flame retardants.
• Reaction in the solid phase: One mechanism is the accelerated breakdown of
polymers.

18. Types of Flame Retardants
• Brominated flame retardants
• Chlorinated flame retardants
• Phosphorous-containing flame retardants (Phosphate ester
such as Tri phenyl phosphate)
• Nitrogen-containing flame retardants (i.e. Melamines)
• Inorganic flame retardants.
These can be further classified as:
• Inorganic, Organo Phosphorous, Halogenated organic and
Nitrogen based compounds.

19. Recipe
• Tetrakis Hydroxy Methyl Phosphonium
Chloride (THPC) - 20 cc / L
• M : L - 1 : 25
• Temperature – Room Temperature
• Time – 30 min
• Pad – Dry – Cure

20. Samples

21. End-Uses of flame retardant
Flame retardant end-uses are-
1. Fire fighters suits
2. Curtain and carpet of cinema hall
3. Military and Airline industry
4. Furniture, Electronic goods and insulation
5. Building insulation
6. Foam furniture
7. Wires and Cabling