flame resistant fibers are materials that have flame resistance built into their chemical structures. Inherently flame retardant fibers swells and becomes thicker, forming a protective barrier between the heat source and the skin.

1. Thermal Resistant Fibres

2. Thermal Resistance
• Thermal resistance is a heat property and
a measure of a temperature difference by
which an object or material resists a heat
flow (heat per time unit or thermal
resistance). Thermal resistance is the
reciprocal of thermal conductance.
• Thermal resistance R has the units
(m2K)/W.

3. Thermal Resistant Textiles
Methods
1. Inherently flame resistant fibres
2. Flame Retardant Finishes

4. Inherently flame resistant fibers
• Mechanism:
• Inherently flame resistant fibers are materials that have
flame resistance built into their chemical structures.
Inherently flame retardant fibers swells and becomes
thicker, forming a protective barrier between the heat
source and the skin.

5. Flame Retardant Finishes
• The other main category is flame-retardant treated (FRT)
fabrics. These materials are made flame-resistant by the
application of flame-retardant chemicals. A chemical
additive in the fiber or treatment on the fabric is used to
provide some level of flame retardancy.
– Borax and ammonium sulfate
– Ammonium polyphosphate (APP)
– Tetrakis (hydroxymethyl) phosphonium chloride (THPC)

6. FR Apparel

7. FR Non-Apparel
25/01/2014 Engr. Shan Imtiaz

8. Temperatures of interest

9. Temperatures of interest
• The effect of heat on textile materials can produce
physical and chemical changes.
• The physical changes occur at the glass transition ( Tg ) ,
and melting temperature (Tm) in thermoplastic fibers at
which chemical changes take place and pyrolysis
temperature (Tp) at where thermal degradation occurs.
• The combustion is a complex process that involves
heating, decomposition leading to gasification (fuel
generation), ignition and flame propagation.

10. Limiting Oxygen Index (LOI)
• “The limiting oxygen index (LOI) is the minimum
concentration of oxygen, expressed as a percentage,
that will support combustion of a polymer.”
• Normal atmospheric air (i.e. the air we breathe) is
approximately 21% Oxygen, so a material with an LOI of
less than 21% would burn easily in air.
• That being said, a material with LOI of greater than 21%
but less than 28% would be considered "slow burning".
• A material with LOI of greater than 28% would be
considered "self-extinguising". “A self-extinguishing
material is one that would stop burning after the removal
of the fire or ignition source.”

11. Thermal and flame-retardant properties of some fibres

12. Definition: Thermal Resistant Fibres
• Thermally resistant organic polymeric
fibres include those that resist thermal
degradation and some degree of chemical
attack, notably oxidation, for acceptable
periods during their service lives.

13. Description
• Thermal resistance derives from their possessing
aromatic and/or ladder-like chain structures that offer a
combination of both physical and chemical resistance
and the former is quantified in terms of high second
order temperatures, preferably above 200 °C or so, and
very high (>350 °C) or absence of melting transitions.
• The fibres described in this chapter are those in which
high strength is not a primary requirement, and includes
some where lower stiffness is needed to give good
textile properties in clothing and upholstery.
• Hot gas and liquid filtration fabrics, braiding materials,
gaskets, protective textiles, conveyer beltings and high-
performance sewing threads are typical end-uses.

14. FR Fibre Classification
• Thermosets
– Melamine–formaldehyde fibres: Basofil (BASF)
– Novoloid fibres: Kynol
• Aromatic polyamides and polyarimids
– Aramid fibres
– Arimid fibres
– Poly(aramide-imide) fibres
• Semi-carbon fibres: oxidised acrylics
• Polybenzimidazole, PBI
• Polybenzoxazoles, PBO

15. Thermosets
1. Melamine–formaldehyde fibres: Basofil
(BASF)
2. Novoloid fibres: Kynol
• Both types on heating will continue to
crosslink and eventually char, hence
giving rise to high levels of fire resistance.

16. Thermosets: Basofil(BASF)
• Basofil®, a synthetic melamine fibre produced
by BASF is “a manufactured fiber in which the
fiber-forming substance is a synthetic polymer
composed of at least 50% by weight of a cross-
linked melamine polymer”.

17. Basofil Fiber Production:
• Basofil®, a synthetic melamine fibre produced by BASF is the result
of a condensation reaction between melamine, a melamine
derivative and formaldehyde, which form a three-dimensional
network typical of thermosetting resins.
• From its chemical structure, the fibre has inherited the characteristic
properties of melamine/formaldehyde condensation resins such as
high temperature and flame resistance, low flammability and
chemical resistance.

18. Notable Physical Properties
This network structure of Melamine fibre produces unique
fibres with excellent inherent characteristics for fire
protection
– Excellent heat dimensional stability and low flammability.
– Superior Thermal Protective Performance (TPP)
– Low thermal conductivity
– Does not shrink, melt or drip when exposed to a flame.
– High Limiting Oxygen Index (LOI) i.e. 32%
– Resistant to chemicals and ultraviolet light.

22. Applications (BASF)
• Fabrics made with melamine add insulation and
protection in technical apparel.
– Fire fighter turnout gear, including gloves and hoods
– Military and law-enforcement protective gear
– Industrial garments and protective workwear
– Racing apparel

23. PBO (Zylon)
(p-phenylene bezobisoxazole)
• ZYLON is a new high-performance fiber developed by
TOYOBO.
• Fibres do indeed exhibit the very high onset of thermal
decomposition temperature of 650 °C and a LOI value
of 68.
• ZYLON consists of rigid-rod chain molecules of poly(p-
phenylene-2,6-benzobisoxazole)(PBO).

25. PBO Polymerization

26. PBO Spinning
• Rigid rod polymers decompose at high
temperatures without melting and can be
dissolved in very few solvent systems
owing to their aromatic structure
• Conventional melt-spinning and solution-
spinning technologies cannot therefore be
used.
• PBO, however, can be spun from solutions
in (polyphospphoric acid) PPA via the dry-
jet wet-spinning technique.

27. Key Properties of PBO
• Excellent mechanical properties
– Impressive thermal properties
– Very high flame resistance
• Excellent thermal stability (onset of
thermal degradation in the 600~700
• Good resistance to creep
• Good reistance to chemicals
• Good resistance to abrasion
– Restricts their use in composites

32. Applications Zylon (PBO)