A Review on Fire Protective Functional
Finishing of Natural Fibre Based Textiles:
Ayan Pal1, Ashis Kumar Samanta1*, A Bagchi1, Pubalina Samanta2 and Tapas Ranjan Kar3
1Department of Jute and Fibre Technology, University of Calcutta, India
2Department of Fashion & Apparel Design, Rani Birla Girls College, India
3Department of Khadi and Textiles, Mahatma Gandhi Institute for Rural Industrialization (MGIRI), India
Submission: July 9, 2020; Published: September 29, 2020
*Corresponding author: Ayan Pal, Department of Jute and Fibre Technology, Institute of Jute Technology, University of Calcutta, India
How to cite this article: AAyan P, Ashis K S, A Bagchi, Pubalina S, Tapas R K. A Review on Fire Protective Functional Finishing of Natural Fibre Based
Textiles: Present Perspective. Curr Trends Fashion Technol Textile Eng. 2020; 7(1): 555705. DOI 10.19080/CTFTTE.2020.07.555705
Cotton, jute and other natural fibre based textile fabrics are gaining popularity in domestic and international field due to its eco-friendliness and biodegradability characteristics and carbon sequestering advantages. This natural fibres based textile fabrics, if can be finished with natural or eco-friendly synthetic fire-retardant chemicals to satisfy the Required standard, it gets an extra dimension in the market and has a huge demand, if it is cost competitive. Cotton, jute, wool and silk based natural fibres have wide differences in their composition and properties and some inherent properties in common are higher flammability, higher moisture absorption and susceptibility to rotting/microbial attack, poor crease recovery etc., which have restricted its growth of their uses towards protective technical/functional textiles, though they have certain genuine advantages too as agrorenewability, bio degradability etc. To find more uses of such natural fibres as high valued technical textiles, as value added technical textiles, these natural fibre based textile fabrics have to undergo certain property modifications by specific improved chemical finishing as required especially for fire retardancy, water repellency, rot resistance etc. depending on its end use applications [1,2]. For the development of various types of functional finishing of jute and other natural fibres that too with eco-friendly formulations and processes, proper choice of eco safe chemicals along with suitable eco safe process parameters and optimization of process variables, water and energy requirement/consumption etc., are must and important for sustainability. So, in this review paper, different aspects of Fire-Retardant finishing of Jute and other natural fibre based textiles and their present perspectives have been discussed.
Keywords: After glow time; Cotton; Char length; Fire retardant finishing; Functional finishing; Jute; LOI values; Pad-Dr-cure process; Natural fibres; Silk; Wool
Now-a-days, fire-retardant textiles are being produced in large quantities due to prevailing legislations for fire safety and public awareness. Demand for fire-retardancy of jute and other natural fibres based materials, is also increasing in market for Eco-Friendly concern. Some important uses as fire protective technical textiles materials besides children apparels are furnishing and cover decorative fabrics as curtain or table cover, jute brattice cloth in mines, pandal fabrics in temporary structure, home-upholstery, automotive fabrics, floor coverings, tents, kitchen apron and gloves etc. , which should preferably be fire retardant.
Before proceeding further for understanding ways and means of Fire Protective action by different types of Fire Retardant Chemicals, the burning cycle of different fibres/polymers and their thermal degradation behaviour for different types of textiles/
polymers must be understood well, to make any attempt to reduce
or to prevent fire propagation/flame spreading on burning of any textiles and preferably the flame be extinguished. Burning of fibres/ polymers by combustion is a complex process involving a multitude of steps, when left unchecked, combustion becomes self-catalyzing cycle and will continue until the oxygen, the fuel supply or the excess heat is depleted and is best described in qualitative terms. Figure 1 is a schematic diagram of the various steps which combine to establish the polymer combustion process. The three essential stages require to initiate the combustion are heating, thermal decomposition or pyrolysis and ignition. Ignition occurs either spontaneously (auto ignition) or due to the presence of an external source such as a spark of a flame/burning flame.
To understand the above burning cycle/mechanisms of each fibres is essential for subsequently finding/determining/selecting suitable flame retardant agent that will be most suitable to act
spontaneously on that polymer/fibres to prevent /stop or to
reduce flaming action/flame spreading action, exact knowledge of
the followings are required
i. Thermal transitions and degradative/pyrolytic
behaviours of each fibre material concern.
ii. Enhancement of pyrolytic temperature/combustion
temperature, if possible, by chemical interaction.
iii. Chemical Interactions of flame-retardant agents with the
fibres for enhancing char formation.
iv. Chemistry of the flame-retardant agents/formulation
and their mode of function
v. Method of application and conditions of treatment for
application of flame-retardant agents.
vi. Use of suitable Catalyst and supportive agents for
required enhanced action at right time.
vii. To make Fire Retardant action to be wash fast by
ensuring fixation of Fire-Retardant agents.
Natural and synthetic textile fibres, are when exposed to a
source of sufficient heat/flame, will start burning and gradually
(depending on their thermal transitions temperatures) will
decompose or ‘pyrolyse’ evolving flammable volatiles to promote
fire/flame, which need to be combat and to reduce or stop rapidly.
(Table -1) provides a list of known thermal transition temperatures
of different textile fibres:
As individual fibre/polymer differ in composition and the
structure their decomposition temperature ranges vary within
certain limits. The rate of pyrolysis will be accelerating leading to
an increasing supply of fuel to the flame which then spreads over
the polymer surface. Major interest for flame retardancy of textile
is the fact that when the textile products burn how to render
them less likely to ignite and if they are ignited, to burn much less
efficiently. The phenomenon is termed as “Flame Retardance”.
Flame retardants act to break the self-sustaining polymer
combustion cycle and thus extinguish the flame or to reduce the
burning rate in a number of possible ways for flame retardant
action on specific textiles to stop or to reduce propagation of
flame during burning of fibrous polymers. So, Flame retardancy in
Textiles may be achieved by the followings ways and means either
by individual or combined mode (a to f) as follows:
a) To use of such fire-retardant materials that thermally
decompose through strongly endothermic reactions. So that heat
required for thermal decomposition is not achieved easily. Tp of
the fibre should not reach and no combustion takes place easily.
For this purpose, Aluminum hydroxide or Alumina trihydrate
and Calcium carbonate and even chain a-clay/alumina etc. is
incorporated as filler in polymers and coatings.
b) To apply of a material that forms insulating layer around
the at temperature below the fibre Tp of the fibres. Boric Acid
and its hydrate salts when heated the low melting compounds
release water vapour and produce a foamed glassy surface on the
fibre insulating the fibre from the applied heat and oxygen.
c) To influence the pyrolysis reaction to produce less
flammable volatile and more residual char to achieve fire
retardancy of textile. This ‘condense phase’ mechanism is in
the action by phosphorous-containing fire retardant, which
after having produced phosphoric acid through thermal
decomposition, crosslink with hydroxyl-containing polymers
altering the pyrolysis pattern to yield less flammable by-products.
Another explanation is the blocking of primary hydroxyl group
in the C-6 position of the cellulose units, preventing formation of
flammable by products (levo-glucosan) these phosphates catalyse
the dehydration and promotes char formation and prevent the
formation of levoglucosan, the precursor of flammable volatiles.
d) To prevent combustion by erecting interference with
the generated free radicals (Br./Cl.) from fire retardant agents
reducing available heat. Such materials act in ‘gas phase’
mechanism, which includes halogen containing fire retardant
compound, which during combustion, yield relatively long
lived hydrogen halides, less reactive free radicals, for effectively
reducing the heat available for perpetuating the combustion cycle
and which decreases the oxygen content in the surrounding air by
halogen/hydrogen halide gas generation.
e) To enhance Tc (Combustion Temperature), the temperature
at which flammable bye products/fibre-fuel reduces, interference
with the flame retarding agent during burning.
f) To modify/enhance of the initial decomposition temperature,
i.e temperature of pyrolysis (Tp), at which prevent/reduces
significant volatile formation and increases char formation/nonflammable
gaseous volatile formation.
Several works are available in literature on flammability and
flame retardancy of textiles like cotton, rayon and other textiles
for centuries. An early description of flame-retardant cellulosic
materials has been found in a British patent granted to Obadiah
WYLD IN 1735. This patent described the use of alum, borax
and vitriol to prevent the flaming of paper, pulp or textiles . In
1821, significant contributions were made to the development of
a flame-resistant finish for linen and jute fabrics by Gay Lussac
 and there the flame resistance was obtained by the use of a
mixture of ammonium phosphate, ammonium chloride and borax.
The earlier ideas of flame retardancy, reviewed by Reeves et al.
 are often defined in terms of coating, gas, thermal and catalytic
dehydration theories. The coating theory may operate by (a),
(b) and (c) functioning singly or in combination. The gas theory
considers retardants which cause gas formation at temperatures
below their ignition temperature (mode (c)) and/or the gases
produced which do not burn at normal flame temperatures but
merely dilute the flame (e.g. CO2, HCl, H2O, SO2 operate by mode (b)
the thermal theory describes retardants which function in terms
of (c) and often these agents undergo endothermic changes such
as fusion, sublimation or loss of water of crystallization. Obviously
release of non-flammable volatiles here will involve pathway (b).
Catalytic degradation describes flame retardants which promote
char and water vapour formation and so involve functions (b) and
Rarely do flame retardants operate by a single mode and
it is more common to refer now days to their retardant activity
functioning in the condensed phase (modes (a), (f), (c)), in the
vapour (or gas) phase (modes (b) and (e)) or both. For instance,
the traditional borax and boric acids/borates mixtures and
similar acid generating salt systems function in the condense
phase by promoting char formation and, in some cases, impart a
glassy impervious coatings in front of the advancing flame [4,5]
their action has been fully reviewed by Pitts  More recently
Nakanishi  has demonstrated that of a variety of commonly
available flame-retardants for cellulose, the boric acid-borax
system is the safest with regard to carbon monoxide and smoke
production during burning.
A general review of the action of non-durable, semi-durable
and durable flame retardants has been carried out by Reeves
et al.  and Kasem & Rouette . The most important group
of flame retardants are those containing phosphorus and in
most fibre/ polymer subtrates, function in the condensed phase
as char promoters. Weil  and Aenishaenslin [10,11] have
comprehensively discussed available types of such agents and their
mechanisms of action. Phosphorous-based retardants function
only if the fibre structure is capable of undergoing transformation
to char and in the case of thermoplastic fibres like polyamide and
polyester, melt and drip which may thus prevent such action.
In many flame retardants the presence of nitrogen has
an additive and, in many cases, a synergistic effect on the
performance of phosphorus containing retardants. Consequently,
many commercially available flame-retardant contain both
phosphorous and nitrogen. This interaction has critically
reviewed by Weil , Khanna & Pearce  and by Einsele 
who specially refers to their activity also in synthetic fibres. Those
organophosphorus flame retardants containing synergistically
active nitrogen and which are particularly suitable for use on
cellulosic textiles, function in more than one way. Current opinion
[13,15] suggests that the nitrogen acts as a nucleophile with
respect to the phosphorous entity thereby creating polymeric
species having polar P-N bonds. The enhanced electrophilicity
of the phosphorous increases its ability to phosphorylate the
C-6 primary hydroxyl group on each anhydro glucopyranose
repeat unit within the cellulose molecule. This prevents the intramolecular
C(6)-C(1) laevoglucosan-forming reaction to occur
which is the main volatile flammable gas produced as fuel formed
during pyrolysis of cellulose. Simultaneously, the Lewis acidicity
of the electrophilic phosphorous promotes dehydration and char
formation. The mechanism of Fire-Retardant action of different
fire-retardant agents acting on Cellulose are described in the
review made by Horrocks and Book edited by Horrocks on fire
retardancy subject [15,16].
Thermal degradation of cellulosic material proceeds through a
complex series of concurrent and consecutive chemical reactions
 which are schematically illustrated in Figure 2 Individual
reactions are influenced by the temperature and rate of heating,
by the environment (particularly oxygen, water and other reactive
or inert gases) and by the composition and physical form (surface
area)of the substrate. Formation of levoglucosan, an important
volatile flammable gaseous intermediate generates by thermal
degradation of cellulose, which takes place at higher temperatures.
According to another report  followings are the general stages
of action of heat on ligno-cellulosic natural polymers & woody
substance (though it may vary from fibre to fibre depending on
the composition and inter unit linkages):
From 55 to 105oC approx. ± 5oC Removal of absorbed
150-200oC Slow start of thermal decomposition of the low
molecular weight compounds of natural polymers/fibres like jute.
>180oC Hydrolysis of low molecular weight polysaccharides
(hemicellulose) begins [Hemicellulose release more incombustible
gasses & fewer tarry substance. According to Saunders and
Allcorn gasses released most frequently contain about 70% of
incombustible CO2 and about 30% of combustible CO].
200-260oC Exothermic reaction begins. [Characterized by
increase emission of gaseous products of decomposition, release
of tarry substance and appearance of local ignition areas of
hydrocarbons with low boiling points].
260-300oC Initial decomposition of cellulose starts.
[Primarily responsible for the formation of flammable volatile
compounds. Uncontrolled release of considerable quantities of
heat begins and increased amount of liquid and gaseous products
(including methanol, ethanoic acid) formed.
300-400oC Active process of decomposition for cellulose
occur and completed. [Ignition of thermal decomposition
products, flame spread by combustible gases and increase in heat
release and mass loss rates].
400-500oC Thermal Decomposition of lignin Starts and
Above 500oC Formation of combustible compounds is
almost nil or very small, however the residual Char formation
In another report, It is mentioned  that moisture is
evaporated from jute in between 30-110oC, hemicellulose show
exothermic hump at around 260-300oC (with DSC peak at 293oC),
though 10% weight loss is obtained in jute at >100oC, after which
decomposition rate accelerates; while the cellulose decomposes
at around 300-380oC(Showing endothermic peak/Hump at 360-
365oC) and lignin decomposition nearly occur at 400-450oC
(Showing exothermic peak/small hump at 420-430oC).
Fire retardancy finishing of jute
Jute brattice cloth used in coal mines. Tent-fabric and
upholstery fabric for fire –safety needs to be finished with a
fire-retardant finish. It is reported that the treatment with
6.75% potassium sodium tartarate (PST) on jute results in a
complete self-extinguishing property. This is not durable, but it
can withstand steaming and brushing. Also, Potassium sodium
tartarate (Rochelle salt) was applied on jute for fire retardancy
. However, this treatment cannot render jute LOI above 30
to show acceptable flame-retardant property. There are several
flame retardant chemicals to improve LOI values for cellulosics
and also applicable for lignocellulosic textiles like Jute using
Borax, Di-Ammonium Phosphate, Borax: Boric Acid (7:3) mixture,
Ammonium sulphamate: Ammonium phosphate (85:15),
phosphoric acid etc. which are either non-durable or semi durable
type, even if applied in conjunction with some binder or cationic
resin finish or using amino silicone binder emulsion. The nondurable
flame retardant is mechanically entrapped, or some way
adhered /anchored onto the fabric surface and thus, becomes
somewhat semi durable if it can be insolubilized on the fabric
surface by suitable after treatment or by suitable binder treatment.
The jute fabric is padded with 5% polyacrylate emulsion (Primol-
HA) along with flame retardant chemicals, a combination of Borax,
Boric acid, Di-Ammonium hydrogen Phosphate=7:3:5 ratio in
proportion of 1:1 then dried at 100oC for 10 minutes and cured at
130oC for 3 minutes it shows reasonable fire retardant property
Among several popular durable synergestic flame retardant
agents available for synthetics and cellulosics, the very useful and
important combinations are
i. Antimony-Halogen compounds or Antimony oxychloride/
Antimony oxide with Chlorine or Bromine salt compounds,
more suitable for Synthetic textiles and
ii. THPC i.e, Tetrakis hydroxy-methyl phosphonium chloride
(THPC), Tris-1-aziridinyl phosphine oxide (APO), APO-THPC
combination APO-Zn (BFn)2 or THPC-Thiourea or APO-Thiourea
combinations, THPC-antimony oxide combination etc.,
more suitable for Cellulosics and lignocellulosic textiles used
widely earlier even in industry. . But none of these are ecofriendly
in today’s context and hence are not used much for
environmental caution and health caution purpose.
So, in jute most of the non-durable and cheaply available
flame-retardant agents may be applied along with the polymeric
or resin finish formulation to obtain durability to some extent.
Also, the use of phosphate with melamine-formaldehyde resin has
been found to be another alternative method for fire proofing jute
goods as studied in BJRI, Dhaka .
The flame-retardant agents available and their
modes of application have been partly reviewed by
Lyons  and also chronologically by Tesoro . More
comprehensive studies are also made available by Drakes &
Reeves , Lewin & Sello  and very recently by Barker &
Drews . Have surveyed uses/application of different fireretardants
of specific nature to their use in the Indian textile
industry. Effect of cellulose, hemicellulose and lignin contents on
pyrolysis and combustion of natural fibers has been described by
Dorez et al. . Very little literature relates to other natural fibres
other than cotton, except review report by Yusuf  including
linen, hemp; silk & wool and by Mehta & Hoque  concerning
flame retardation of jute.
Different fire-retardant chemicals act in different way by
manipulating pyrolysis, prevention of flammable gases, less
or more char formation, controlling combustion, protecting/
preventing generation of flammable gases or from heat/oxygen
and fuel to combat burning/propagation of flame. The mode
of action of such fire-retardant chemicals may therefore be
i. Nitrogen-synergised phosphorylation of cellulose to block
ii. Lewis acid-catalysed dehydration plus some chain
degradation to short chain oligomers not conducive to
iii. Cellulose cross-linking following phosphorylation which
promotes both char formation and its consolidation.
iv. The 2nd most important group of flame retardant are those
which contain halogen atoms, notably chlorine and bromine.
These operate in the vapours phase by release of hydrogen
halide gas and free radicals which suppress the flame
reactions. The efficiency of such retardants is enhanced by
the presence of either phosphorus or antimony (antimony
(III) oxide). Both antimony-halogen and phosphorus-halogen
has been reported to be synergistic. Khanna  reviewed
the evidence for synergism and suggest that antimonyhalogen
activity arises from formation of the oxyhalide, SbOX,
where X is the halogen. and mentioned optimum activity to
occur for various substances at a molar ratio of Sb:X=1:3
suggesting formation of SbX3 as an essential stage in the
retardation chemistry. It would seem that initial formation
of SbOX, X is followed by conversion to SbX3 which control
release of halogen, which on decomposition scavenges flame
propagating radicals such as H and OH. The char-promoting
tendency or phosphorylation or both of these systems of fire
retardancy action have been observed in certain polymer
systems including cellulose and lignocelluloses for different
types of fire-retardant agents discussed here.
It has been found that phosphorous based compounds are
effective flame retardant [29-31] for cellulosic materials. The
most effective theory which has been generally accepted is
that phosphorous compounds are acid precursors and these
acids participate in char formation by dehydration. It has been
suggested by many investigators that the addition of nitrogenous
compound results in improved flame retardancy. The same level
of flame retardancy can also be obtained with reduced quantities
of phosphorous in the P-N system. This behaviour which is termed
as “Synergestic Behaviour” of phosphorous and nitrogen has
been found in the case of various flame retardants comprising
phosphorous-nitrogen system .
Phosphoric acid and the ammonium salt of phosphoric acid
are very effective in inhibiting fire propagation for cellulose
[33,34]. Lewin et al.  reported that the two decades following
the 1950 period were the golden age of the synthesis and
development of phosphorus containing flame retardants and in
particular, those for cellulose. Since mid-1970’s, very few new
developments have taken place and most currently available and
successful commercial durable retardants were discovered during
the former period.
Samanta & Bagchi et al  has also described successful semidurable
fire-retardant finish of jute fabrics using phosphorous and
nitrogenous compounds and studied their thermal degradation
behavior up to 500oC. Phosphoric acid [24,36] and its derivatives
in the presence of nitrogenous buffer will esterify cellulose under
elevated temperature curing conditions with minimum acceptable
degradation. Reid et al.  also mentioned phosphorylation of
cellulose forming cellulose phosphoric esters having the typical
Also, the stannate-phosphate process is reported to give
durable flame-retardant finish. The cotton fabric is padded with
Sodium Stannate and ammonium sulphate followed by drying
and then the fabric is further padded with diammonium hydrogen
phosphate and urea  followed by curing. A combination
of Urea-phosphate-formaldehyde resin treatment imparts an
excellent durable flame-retardant property in cotton fabric .
Isaac et al.  observed that if undertaken simultaneously
with sulphation, ion exchange problems are rendered tolerable.
In this system sulphation by ammonium sulphamate, NH2SO3-H,
is enhanced if phosphorylation is carried out with phosphoric
triamides; diammonium phosphate may not be used because
it cannot suppress the afterglow associated with the cellulose
sulphate groups and the phosphorylation itself is impeded by
the sulphamate. Afterglow in sulphated cellulose is associated
with sodium ion exchange from soft water laundering liquors
and in this system minimal afterglow and acceptable durability is
achieved if Sulphur is present at about the 2% level and P/S mass
ratio of 1.3-2.0 on cellulose is maintained. O’Brien investigated the
durable flame resistance and other physical properties of cotton
and rayon treated with cynamide and phosphoric acid . The
dyed cotton fabrics were treated finish with urea with phosphoric
acid  for a durable flame-retardant method. The role of urea
was that of a solvent which helps to reduce acidity and swells
cellulose to enhance penetration.
Durable Organo-Phosphorous Fire Retardants: Tetrakis
(Hydroxymethyl) Phosphonium Derivatives
One of the important FR agents which provide durable flame
retardancy is Tetrakis (Hydroxymethyl) Phosphonium chloride
(THPC) which is initially described in 1921 by Hoffman 
and recognised as having commercial potential by Reeves &
Gutherie . It is prepared as a crystalline solid from phosphine,
formaldehyde and hydrochloric acid at room temperature .
THPC is highly reducing in character and its methylol groups
condense with amines to form insoluble polymers. Consequently,
it is applied to cellulose substrate in presence of amine ended
species followed by curing to promote condensation and crosslinking.
THPC forms the basis, therefore, of not only a variety
of systems in which it is directly present, but also the principal
derivatives Tetrakis (Hydroxymethyl) Phosphonium Hydroxide
(THPOH) and the respective Sulphate THPS. FR finishes based on
THPC-Amide, THPC-APO, THPC-Cyanamide and THPC-Sb2O3 have
been used mostly for durable application of cotton fabric.
However, Fire Retardant finish with such THPC or other
phosphorous compounds with or without nitrogenous
i. Loss in tensile strength.
ii. Release of formaldehyde.
iii. Acid tendering of fabric during curing.
iv. Fabric handle become stiff.
Complete neutralization of THPC with Sodium Hydroxide
yields a compound generally referred to as THPOH . THPOHammonia
has received a great deal of commercial attention due
to strength retention and the fabric does not stiffen. This flame
retardant is applied by padding fabric with a solution of THPOH
and various auxiliaries, then partially drying the fabric, and finally
exposing the partially dried fabric to ammonia gas . THPOH–
ammonia-Copper Complex: Copper salts were found to stabilize
THPOH-NH4OH solution by forming a complex, thereby making it
possible to apply THPOH  to cellulose substrate from a single
bath without the use of gaseous ammonia.
Proban process: The replacement of heat curing by ammonia
gas curing removed the problem of fabric tendering because of the
ambient temperature is required and high accompanying pH ; the
application of THPC and urea followed by an ammonia cure has
been admirable developed as the Proban process patented and
licensed by Albright and Wilson Ltd .
Phosphonic acid derivatives: Phosphonates are playing
important role in the durable flame -retardant treatment of
cellulose. Phosphonic acids have two reactive group which can
be esterified or converted to amide. Aenishaenslin et al. 
showed that N methylol derivatives of dimethyl and diethyl
phosphonopropionamide and the corresponding 1-methyl
propionamide are the most suitable flame-retardants for cotton. It
is preferable to apply N-methylol dialkyl phosphonopropionamide
(marketed by Ciba under the name Pyrovatex CP) in conjunction
with aminoplast resin in order to increase nitrogen content of the
treated fabric and the effectiveness of flame retardant. Pyrovatex
CP are effective on all cellulosic fibres .
Aziridines: Anther durable fire retardant for cotton is Tris
(1-aziridinyl) phosphine oxide (APO) . APO is highly reactive
compound and can be used with cellulose by acid catalysed
heat curing technique. However, the uses of THPC and APO are
restricted now a days due to their toxicity problem.
Common commodity cellulosic and lignocellulosic fabrics can
be made fire-resistant by treatment with different non-durable
and durable fire-retardant formulations, which are readily
available in literature as cited above. However most common
chemical used for obtaining wash fast Flame Retardancy on
cotton, Viscose, Jute, Wool, Silk etc., is a common THPC based
compound (Tetra–Kis-Hydroxy methyl phosphonium chloride)
commercially sold in different names by different companies
(say Proban-210, Pyrovtex-CP, Sara flam-CWF, etc) and is used
with an acidic catalyst by Pad-Dry (100oC for 10-15 min)–Cure
(130oC-150oC for 3-5mins depending on Fabric weight/aearial
density) technique followed by washing-drying and calendaring.
But the THPC type of Compounds are becoming now obsolete,
as it contains Methyl-Hydroxy groups i.e Methylol group and has
therefore Formaldehyde release problem afterwards and hence
been not eco-friendly. Here is the need started again for new
research for finding low cost Fire-Retardant Chemicals which is
eco-friendly as well as can impart wash fast fire retardancy to such
natural fibre based textiles.
There are several non-durable flame retardant chemicals for
low cost jute products such as –Borax, Di-Ammonium Phosphate,
Borax: Boric acid (7:3) mixture, Ammonium sulphamate:
Ammonium phosphate (85:15), phosphoric acid etc. which if
applied in conjunction with a reactive resin, the non-durable
flame retardant is embedded in the binder/resin film on the fabric
surface and thus, renders it somewhat semi-durable fire retardant
finishing effect to jute. The jute fabric is when padded with 5%
polyacrylate emulsion (Primol-HA) along with a combination of
Borax, Boric acid, Di-Ammonium hydrogen Phosphate=7:3:5 ratio
in proportion of 1:1 then dried at 100oC for 10 minutes and cured
at 130oC for 3-4 minutes it shows reasonable degree fire retardant
But after understanding need of eco-friendly fire-retardant
finishing of jute and cotton as a natural fibre, further researchers
are concentrated on non-THPC and Non-APO or Non-Halogen
based fire-retardant finishing of jute and cotton fabrics. Recently,
for establishing toxicity free fire-retardant finishes on natural
fibre based textiles, formaldehyde free fire-retardant finishing
has been encouraged for environmental concern . Some
fundamental study on the thermal behavior [53-54] of scoured/
bleached and fire retardant treated jute substrate by analysis DSC
and TGA thermograms have been reported to understand the
chemical interaction of specific treatment on thermal degradation
temperatures of different constituents of jute substrate.
Phosphorous–Nitrogen based i.e Diammonium phosphate and
Urea combination of fire retarding treatment as common fire
retardant finishing  of jute has been described in literature
including as a semi durable fire retarding finish using different
ratio of phosphorous and nitrogen compounds on bleached
jute fabrics. Horrocks  has made a comprehensive review of
different fire-retardant materials and their mode of action and
effects on textile fabrics. Role of char formation in Fire-Retardant
finishing of textiles has also been elaborated by Horrock .
Extensive research has been now concentrated to develop newer
eco-friendly fire-retardant formulations in all different ways and
means possible, some examples are as follows:
Eco-friendly Fire-retardant finishing of Jute Fabric by
Impregnation or coating Phosphorylated PVA and its effect on
physical properties and thermal behaviour of treated jute fabric
has been reported by Samanta & Bhattacharyay (Roy) et al. .
Fire retardant finishing of Jute based fabrics using Ammonium
Sulphamate or sulphamic acids and Urea Combination and
its process standardization for application on jute has been
preliminarily reported by Samanta and Bhattacharyay(Roy)
et al.  in recent past as a need of the hour considering the
environmental protective action concern. Optimization of this
fire retardant formulation with ammonium sulfamate and urea
combination using statistical experiment of design software
has been further reported by applying User Defined Quadratic
Model (UDQM) tools for deriving response surface methodology
equations to predict LOI value, Char length and Loss of Fabric
tenacity for specific concentration of Ammonium Sulfamate and
Urea with prefixed dosages of MgCl2 catalyst in recent report by
Samanta and Bhattacharyay (Roy) et al. .
Use of nano technology applications by preparing and
applying nano ZnO powder for obtaining fire protective finish of
jute fabrics with 0.01% Nano-ZnO Powder admixed with 4-6%
poly-hydroxy amino siliconate binder have been described also
by Samanta, Bhattacharyaya (Roy) & Josh et al.  to establish
toxicity free nano technology based fire-retardant formulations
for jute fabrics. Optimization of this fire retardant formulation
with Nano-ZnO Powder and poly-hydroxy amino siliconate binder
combination using statistical experiment of design software
has been further reported by applying User Defined Quadratic
Model (UDQM) tools for deriving response surface methodology
equations to predict LOI value, Char length and Loss of Fabric
tenacity for specific concentration of Nano-ZnO Powder and Polyhydroxy
amino siliconate binder with MgCl2 used as catalyst by
Samanta , Bhattacharyay(Roy) and Bagchi et al. .
The mode of functions of specific flame-retardant finishes
and its wash durability specifically for cellulose, wool and manmade
fibres and their blends are described in depth by Horrocks
. Multipurpose finishes for both cellulose and wool textiles
in which flame retardancy is one property along with other
finishing effects conferred on the said textiles are examined in
this literature where finally the effects of applying these specific
flame-retardant finishes on textile related properties of the said
textiles and their fire retardant performances are also reported.
Khalifah Gaan & Malucelli  have described a detailed review
on recent advances for flame retardancy of textiles based on
phosphorus chemistry and their mechanism as well as their
thermal degradation behavior in 2015.
Sustainable flame retarding finishing of cotton and Jute
utilizing agro waste like banana pseudo stem (BPS) containing
phosphorous, nitrogen, chlorine, silicate, and other many
metallic compounds was applied [65,66] on premordanted (5%
tannic acid+10% alum) cotton cellulosic and jute lignocellulosic
textiles by the pad-dry method in an alkaline condition have been
reported to render LOI value up to 30 to Cotton and LoI value up
to 33 to jute making natural bio-Fire Retardant finishing of Jute
and Cotton. The flame retardancy of these samples was measured
in terms of LOI, burning rate, total heat production and its thermal
degradation was evaluated by differential scanning calorimeter
(DSC), and Thermogravimetric analysis (TGA).
Eaton et al.  gave a comprehensive article on various
test methods aimed at different sectors of industry to produce
the wide range of flame retardancy test methods and standards.
Ozcan et al.  studied that fabrics produced from coarse yarns
will burn more easily than those from fine yarn because of their
loose structure. Yarn count and twist factor made an influence on
ignition time at the knitted fabrics increasing yarn counts decrease
the ignition times and the best ignition times are obtained for yarns
with a 3.6 twist coefficient. Mehta  has briefly considered
different aspects of fire-retardant finishing with special reference
to polyester and cotton.
Benisek et al.  show how different fabrics and finishes
behave in protective clothing, designed to resist radiative, corrective
and conductive heat. Dawn et al.  analysed the provision and
properties of cotton protective apparel designed for the US Space
Shuttle. They thoroughly assess the acceptability of cotton finish
with a Tetrakis (hydroxymethyl) phosphonium sulphate-ureaammonia
cure system for this most stringent end use. Stephenson
et al.  surveyed both non-durable and durable treatments
for non-woven products with special reference to cellulosics and
polyester. Mehta et al.  reviewed the toxicological hazards of
flame retardants are often questioned in term of the toxicity of
the basic retarding chemicals and the hazards during application
and end use. They studied for commonly available cellulosic flame
retardants and mentioned agent like tris (aziridinyl) phospine
oxide (APO) and antimony oxide can be entirely toxic. Nuessle
et al.  showed that phosphorylation by means of cellulosediammonium
phosphate reaction in the presence of urea gave rise
to a flame retarding finish.
Kaushik et al.  have studied that a THPC-Thiourea based
formulation is applied to the polyester-viscose blended fabrics
by pad-dry cure procedure followed by washing to produce. FR
fabrics, which retain their retardancy offer as many as fifty through
laundering and trumble drying. THPC-Thiourea finish imparts
the durable flame retardancy by crosslink-OH Group of cellulose
portions of polyester/viscose blended fabric due to which about
15% loss in tensile strength of treated fabrics. Comparative
Studies of flammability behaviour and physical properties of
controlled, treated and washed fabrics are done under the different
conditions. Ramchandran et al.  studies through two different
methods for flame retardant finish to cellulosic fabric. Among this
novel methods, the results proves that the Urea with phosphoric
acid method is found to be the best method for durable flame
retardant finish to cellulosic fabrics than stannate and phosphate
step method in terms of higher flame resistance and better tensile
properties and also reduced stiffness character.
Blanchard et al.  studied that cut pile cotton/polyester
carpeting burns over the entire area upon ignition if the pile
density of the carpet is sufficiently low. Chemical modification by
esterification of cellulosic fibres results in restricted combustion
properties. This allows such substrates to pass the standard
flammability test for carpets and rugs. Cotton containing carpeting
spray treated with only 5-10% polycarboxylic acid and suitable
catalyst exhibits satisfactory flame suppression properties.
Appropriate polycarboxylic acids are 1,2,3,4-butane tetra
carboxylic acid (BTCA), Citric Acid and maleic acid with catalyst
such as Sodium hypophosphite, sodium phosphate, or the partially
neutralized salt of the acid. Chemical reaction and processing
conditions required to achieve improved flame resistance on
cotton-containing cut pile carpeting are presented. Domobrowski
 discussed that there is a common assumption about the
dangers of decabromodiphenyl Ether (DECA). It is the purpose of
this paper to present an alternative viewpoint relative to the use
of this halogenated flame retardant (FR). Brominated FRs such
as DECA inhibit the chemical reaction between oxygen and fuel,
preventing a fire from developing. Flame-resistant cotton fabrics
have been prepared by Frick et al.  for treatment of the fabric
with an aqueous emulsion of an organic polymer for fire retardant
finishing, prepared from bromoform and triallyl phosphate. This
finish is proved to be durable to repeated laundering and does not
materially change other textile properties rendering satisfactory
fire-retardant action. This treatment is said to be applied by
conventional textile finishing equipment in industry.
Peixiu Tian et al.  evaluated the flammability of a cotton
fabric finished with a flame retardant (FR) of ammonium salt of
teraethyiene pentamine heptamethyl phosphonate (ATEPAHP),
that has been grafted on cotton fabric via a P˗O˗C covalent
bond. Where limiting oxygen index (LOI) of this treated cotton
having 18%˗26% weight gain in ATEPAHP achieved LOI value
37.0%˗40.5% and this LOI value is reduced to 28.2%˗31.8% after
50 laundering cycles (LCs) proving it still as fire retardant even
after 50 cycles of wash. Bajaj et al.  studies that Diammonium
hydrogen phosphate (DAP) and N-methylol resins were applied to
cotton and polyester/cellulosic blends using one step and two step
sequential pad-dry-cure process. Among the N-methylol resins
studies, only urea formaldehyde treatment on phosphorylated
cotton demonstrated the phenomena of N-P synergism in terms of
oxygen index, while no clear trend could be established in blends.
Nakanishi et al.  studied the flame retardant of cotton
fabric with nitrogen, phosphorous, sulfur, halogen and boron
based compound individually or in combination of two component
showed sufficient flame retardancy to cotton fabric and the flame
retardant samples exhibit difference in thermal degradation
behavior compared to untreated fabric. Kaur et al.  revealed
that phosphorylation of cotton fabric as well as grafted cotton
fabric through graft co-polymerisation with methacrylamide
improved fire-retardant property. Eaton  mentioned the
different flame retardancy test methods for textiles. Blanchard
et al.  studied phosphorylation of cellulose with phosphonic
acid derivatives and the physical properties have been discussed.
Discoloration upon curing of phosphorylated cotton is reduced by
incorporation of 1-4% of dicyandiamide.
Mamalis et al.  mentioned that the flame-retardant
finishing of cotton affected different mechanical properties e.g.
tensile, bending, shear, compression and surface properties.
James R House et al.  studied the effectiveness of commercial
flame retardant Proban on cotton clothing and concluded that
Proban FR treatment was not damaged by wear and washing.
Giraud et al.  studied the flame retarding behavior of cotton
coated with polyurethane containing microencapsulated flameretardant
agent. Synergism behaviour of P-Br in polyester-cotton
fabric treated with tetra bromo bisphenol (TBBA), TBBA- DAP
was studied and maximum synergism was obtained when the
concentration of TBBA was equal to DAP . Garba et al. reported
 that some degree of flame retardancy on cellulosic material is
achievable with crosslinking agents such as dimethyl dihydroxy
ethylene urea or even di methylol urea.
Post grafting reaction of Glicidyl-methacrylate (GMA) grafted
cotton fabric with ethylene diamine followed by orthophosphoric
acid were carried out by Reddy et al.  to produce fire retardant
cotton fabric. FTIR analysis of gases evolved from cotton and
flame retarded cotton fabric pyrolysed in air was carried out by
Horrocks et al. . Kandola et al.  studied the influence of
treatment of flame retardant to cotton on the mechanism of cotton
pyrolysis. Photochemical grafting of 4-vinyl pyridine onto cotton
fabric for imparting flame retarding properties has been reported
. Nakanishi et al. [92,93] studied thermal degradation of
cotton as well as flame retarded cotton and revealed that flame
retardant cotton samples show extremely reduced amount and
fewer numbers of gas products compared with untreated samples.
Rearick et al.  have studied the flammability considerations
for raised-surface apparel. Raised surface and light weight apparel
are regulated under the General Weaving Apparel Standard
(GWA). Currently for cotton raised surface (RS) apparel, the most
common method for meeting the GWA standard is to blend cotton
with synthetic fibres. But many companies would like 100%
cotton RS garment that pass the GWA flammability test.
From the above literature review, it is clear that amongst
amples of fire retardant chemicals so far studied and some of
them were established, currently for all newer development of
fire retardant finishing approaches are concentrated to find low
cost commercializable eco-friendly fire retardant finishing of
cellulosics and ligno cellulosics and protein based natural fibre
constituted textiles. Though many approaches stands to be useful,
it need to reestablish its technoeconomic feasibility and wash
stability satisfying National/International Standards on it as per
particular specifications of fire resistant performance properties
of selective different end uses, practically to come into effect for
commercial uses and customer acceptability.
An acceptable Fire Retardant Textile Materials should exhibit
LOI value nearly 35 and char length 2-4cm , afterglow time 15±5
sec with minimum loss of fabric tenacity and loss in tear strength
( Both loss in fabric tenacity and loss in tear strength preferably
be restricted within 20±5% after fire retardant treatments done).
However, for different end uses, specifications of respective fireretardant
textiles are different. However for cellulosic and other
natural textile fibre based materials, it is necessary to standardize
the recipe and methods for application of fire retardant finish
separately particularly for cotton and its blends, and jute and
jute/cotton union fabrics and again for silk and woolen textiles
and their blends separately, as any single or one recipe and
process conditions for any particular textiles will not match
the requirement of other textiles, due to their compositional
differences of each. Such value-added fire retardant natural fibre
based fabrics may find new markets and better acceptability in
international and national market, if such fire resistant as one of
the important functional properties are imparted and proved to be
eco-friendly. However, at present, there is no separate standards
available for Eco-friendly fire retardant finish, so presently a fire
Retardant finished textiles if need to get certified as eco-friendly
finishes, it has to satisfy two different standards at a time, i.e it
has to first meet/satisfy the parameters concern to fire retardant
performances as per suitable National/International standards as
per end uses and then for proving its eco friendliness, it has to
meet and specification for parameters of Eco Mark scheme/OTN-
100 or GOTS parameters as well. Such Fire-retardant finished
textiles again need to be achieved / produced at reasonable cost
for market acceptability.
Hence, there is a need of continuous search/research for
developing suitable recipe and methods with standardizing the
process conditions for establishing suitable eco-friendly chemical
formulations for production of such fire-retardant natural fibre
based Cotton/Jute/Wool/Silk textiles and their blended fabrics that
may be used as decorative furnishing in public places like school/
colleges, hotels. public community hall/auditorium, hospitals etc.,
or as Home textiles for use as curtains and table and sofa covers
for home furnishing or for kitchen apron and gloves etc., besides
transport furnishings such as Car /Rail/Aviation upholstery, and
in many such other end-uses, besides fire fighter dresses (though
the standard required for each end uses will differ). Thus, the need
of future direction of research required in this field is identified
and justified here to motivate current researchers in this field.
Samanta AK, Bhattacharyya (Roy) Reetuparna, Chowdhury Ranjana (2014) Eco-friendly Fire-Retardant Finishing of Jute Fabric by Impregnation or Coating Phosphorylated PVA and its Effect on Physical Properties and Thermal Behaviour of Treated Jute Fabric. International Journal of Applied Engineering Research 9(4): 439-450.
Samanta Ashis Kumar, Bhattacharyya (Roy) Reetuparna, Bagchi A, Chowdhury Ranjana (2020) Statistical Optimisation of Ammonium Sulfamate and Urea Based Fire Protective Finishing of Jute Fabric by User Defined Quadratic Model (UDQM). In: Majumdar A,Gupta D,Gupta S(eds.),FTC-2020 International Seminar (at IIT-Delhi) Proceedings being published as book chapter in Functional Textiles and Clothing. Springer-Nature, Singapore.