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Fire-Protective and
Flame-Retardant Coatings – A
State-of-the-Art Review
EDWARD D. WEIL*
Polymer Research Institute, Polytechnic Institute of New York University, Six
MetroTech Center, Brooklyn, NY 11201, USA
(Received September 1, 2010)
ABSTRACT: This review covers mainly intumescent coatings, with briefer
discussions of non-intumescent organic fire-resistive coatings and cementitious
inorganic coatings. Emphasis is placed on the more recent developments, and the
more recent patent literature is surveyed. Modeling and optimizing are covered
both from basic and applied aspects. The chemistry of the production of a foamed
char barrier is discussed. Enhancing the performance by adjuvants and choice of
binders is shown to be possible. The important interactions of ammonium
polyphosphate with other components such as titanium dioxide are described.
Testing is briefly discussed, as are some shortcomings of present-day coatings,
such as limited water resistance, and some opportunities for improvement.
KEY WORDS: intumescent coatings, spumific, carbonific, ammonium poly-
phosphate, heat transfer, melamine, char, adjuvants, silicates, borates, titanium
dioxide, expandable graphite, binders, ceramic coatings, textile coatings,
firestops, gelcoats.
INTRODUCTION AND SCOPE
P
ASSIVE FIRE PROTECTION includes coatings and firestops, as well as the
use of inherently flame-retardant materials. Flame-retardant plastics
and textiles have been covered in a recent book by Weil and Levchik [1].
Fire-retardant coatings for wood have been briefly reviewed in the
*E-mail: ew18@uakron.edu; eweil@poly.edu
J
OURNAL OF FIRE SCIENCES, VOL. 29 – May 2011 259
0734-9041/11/03 0259–38 $10.00/0 DOI: 10.1177/0734904110395469
ß The Author(s), 2011. Reprints and permissions:
http://www.sagepub.co.uk/journalsPermissions.nav
broader context of fire safety of wood construction by USDA Forest
Products Laboratory researchers in the 2010 Wood Handbook [2]. Wood
coatings more often are designed to retard ignition and rate of burn
rather than to provide the fire-resistive barrier which is more typical of
steel coatings.
Traditional fireproofing coatings are cementitious coatings, based on
Portland cement, magnesium oxychloride cement, vermiculite, gypsum,
and other minerals. Fibrous fillers, supplementary binders, and density-
controlling and rheology-controlling additives are typically mixed with
water on site and applied by spraying during steel construction at
thicknesses of one-half inch or more. The Underwriters Laboratories Fire
Resistance Directory calls them Spray Fire Resistant Materials (SFRMs).
Some of these coatings can be applied onto a flammable substrate by the
use of rollers and/or a moving belt. These coatings can provide fire
protection from one-half to several hours by water release and thermal
insulation effects. They are low in cost and easy to apply, and some are
resistant to weather exposure. However, because of their weight,
thickness and poor esthetics, they limit architectural design. Building
designers avoid them for visually exposed steel. They may also be
dislodged in a violent fire. Further discussion of these mineral coatings
is outside the scope of the review, as are rigid mineral-based boards, fire
blankets, or loose-fill flame-retardant insulation as passive fire protection.
A useful although brief discussion of SFRMs as well as intumescent
coatings and their UL classification is found in a Carboline paper [3].
Firestops and flame-retardant gelcoats are briefly discussed in this review.
This review will put the main emphasis on coatings, particularly
intumescent coatings (which swell to a thick insulative foam when
heated above a critical temperature), but will briefly discuss other types
of coatings which are flame retardant but not intumescent. Both these
types of non-mineral coatings can be applied by qualified painters, and
can offer good appearance and durable surfaces. The US market has
been underdeveloped for intumescent coatings for steel in buildings
because of the predominance of concrete construction, relative cost, and
possibly lesser familiarity by architects.
Another main classification of fire-protective coatings is based on
their desired performance, namely: (1) those that increase the fire
resistance as defined by ASTM E119 for buildings or by ASTM E1529 for
hydrocarbon fires and measured in terms of time, i.e., 1 h, 2 h, etc., and
(2) those that reduce the flame spread of the combustible substrate, such
as wood, as measured by the flame spread index of ASTM E84 in the
USA. Fire-protective coatings can also be classified from the standpoint
of the type of fire being protected against: (1) the ‘wood fire’ such as
260 E. D. WEIL
might occur from burning furniture, paper, cloth, etc., (typically
represented by the E119 test, discussed later), and (2) the ‘hydrocarbon
fire’ from burning petroleum (typically assessed by the E1529 test, also
discussed later). Both classifications have considerable overlap.
Typically, coatings protective (or retardant) against cellulosic-type
fires are applied in thin film coats up to 1.5 mm (60 mils) thick. These
coatings are usually not very weatherable; so, for outdoor applications, a
protective topcoat is needed. Coatings protecting against hydrocarbon
fires are typically two-component (usually epoxy) systems applied
solvent-free at 8–10 mm (320–400 mils) per coat often through separate
heated lines with an in-line static mixer at the spray tip. The steel
surface should be prepared by an abrasive blast, and then an
anticorrosive primer should be applied. After application of the fire-
protective coating, a topcoat (for example, an acrylic polysiloxane finish)
may be applied. These coatings may be applied off-site or after the steel
framework has been erected. A properly applied coating of this type is
suitable for offshore oil and gas facilities, being quite resistant to
hydrocarbons and to seawater.
BACKGROUND
The classical review of intumescent coatings is a 1971 paper by
Vandersall [4] (Monsanto). He presents the early history and the
detailed course of development of commercial intumescent coatings,
mostly based on a char-forming carbonaceous material (‘carbonific’), a
mineral acid catalyst, a blowing agent (‘spumific’), and a binder resin.
This review is replete with formulations and is still a rich source for
ideas for formulation improvement. At the time of Vandersall’s review,
typical commercial intumescent paint formulations contained several
pounds per gallon of intumescing components, and required thick and
costly coatings. Much empirical research has been done in industry and
a few academic laboratories to optimize intumescent coatings, to find
alternative char-formers, catalysts and blowing agents, optimized
binders, activators, and residual barrier-forming additives. Parallel
work has been done outside of the coatings area to apply the
intumescent approach to flame-retarding polyolefins, olefin copolymers,
elastomers, and ‘firestops’ (barrier materials for closing wall apertures).
We have reviewed polyolefin flame retardancy previously in this journal
[5] and, with elastomers included, in a subsequent book [1]. In view of
this prior coverage, this review will concentrate on coatings with some
attention to firestops.
Fire-Protective and Flame-Retardant Coatings 261
More recent reviews have covered, usually not in the detail
of Vandersall, the commercial applications of fire-retardant and
fire-resistive coating. It is our intention to emphasize the more recent
developments and those which seem to be of greatest practical value.
The theoretical and basic topics are covered by reference to published
studies without repeating them in any detail.
A useful review from a commercial viewpoint has been presented by a
marketing manager in this field [6]. The importance of architectural
design – the esthetics of exposed steel – is discussed, as well as the
question of on-site versus factory application.
Fire protection engineering overviews, comparing cementitious fire-
protective coatings to intumescent coatings, are available from both
before [7] and after the 9-11-01 disaster. Subsequent to 9-11-01, much
attention was given to this question; a critical review by the National
Institute of Standards and Technology was published in 2004 [8] and is
available as a book.
A 2007 review [9] of specialty coatings for fire protection covers the
entire range of fire-retardant and fire-protective coatings, with realistic
discussion of needs, markets, market dynamics and trends, codes and
other regulatory issues, and types of products available, with profiles of
major US suppliers and their product lines.
NON-INTUMESCENT FIRE-RETARDANT COATINGS
A broad but not highly detailed overview of flame-retardant/fire-
resistive coatings is presented by Green [10] who showed that even
conventional paints can reduce flame spread below that of an unpainted
flammable substrate, but for demanding situations such as on ship-
board, coatings deliberately formulated for low flame spread index are
preferred. On shipboard, paint is repeatedly applied to prevent
corrosion, and fire-resistant coatings using halogen–antimony flame-
retardant systems are commonly used. The halogen component may be a
vinyl chloride–vinyl acetate copolymer, a chloroparaffin, or a chlorine-
containing alkyd. Formulations are given for fire-retardant latex paint
and alkyd-based paint. Formulations of this sort used by the US Navy
and improvements in the 1990 period have been described in 1996 [11].
A typical shipboard paint of a type probably still used by the Navy (MIL-
DTL-24607B) [12] contains a chlorinated alkyd such as Reichhold’s
Becksol
Õ
91160-00, titanium dioxide, alumina trihydrate (ATH),
magnesium silicate, calcium borosilicate (Halox
Õ
CW-2230), calcium
metaborate (Buckman’s Flame Block
Õ
BL-381, various pigments,
262 E. D. WEIL
thixatropes, surfactants, solvents (such as Oxychem’s Oxsol
Õ
100,
p-chlorobenzotrifluoride), and driers shown in the specifications.
Coatings using high mineral loadings are another means for attaining
flame resistance. A formulation of 18.6% rutile (TiO
2
), 12.7% barium
metaborate, 8% aluminum silicate pigment, 21.1% polyvinyl alcohol
(PVA), and several wetting agents and dispersants with 25.2% water
was published for an interior flat wall paint in 1992 [13].
Resistance to ignition and flame spread on wood is said to be provided
by an aqueous coating using ATH, antimony trioxide, and calcium
carbonate with a vinylidene chloride–acrylate binder in a 1987 patent
[14]. The coating is said to be suitable for exterior application.
A German research institute [15] has developed a fire-protective
coating for wood based on ceramicizing compositions of sodium borate
and silica plus optional phosphorus ester or salt components, using
various aminoplast or urethane resins as binders.
A commercial additive CEEPREE
Õ
, a borosilicate glass with low
softening point, has been available since its original development at ICI
[16]. This additive is useful, for example, in mastics for protection of
steel against very hot (fuel) fires, providing some protection after
organic material has burned away [17].
Protection of metals from corrosion while avoiding fire propagation
can be accomplished by a thin coating of ethylene–chlorotrifluoroethy-
lene copolymer (Solvay Solexis’s Halar
Õ
), which chars when exposed to
fire. Even coatings as thin as 10 mils can be effective [18].
Basic Studies on Intumescent Coatings
Basic research has been of two main types, one emphasizing the heat
transfer aspects and the other the chemical aspects. A broad review
dealing with both aspects, as well as practical considerations, has been
published by a University of Lille group [19].
Heat Transfer Studies With Intumescent Coatings
A group experienced with aerospace vehicle protection developed
a semi-empirical computer model of the intumescent coating perfor-
mance taking into account mass and heat transfer, swelling kinetics,
and the reradiation of incident energy when a highly emissive char
was formed. Experimental weight loss measurements and estimated
thermophysical and chemical parameters were used as input, and
the model was shown to predict backface thermal histories to within
20% of the experimentally measured values. Total expansion and rate
Fire-Protective and Flame-Retardant Coatings 263
of expansion were found to be important parameters for providing
thermal protection [20].
Another group with aerospace background conducted an extensive
experimental program together with a simplified heat- and mass-transfer
modeling (a ‘frontal model,’ assuming a thin pyrolysis region which
moves from the coating’s surface to the substrate) [21]. The experimental
work used a heat source typical of aviation fuel fires and measured the
temperature–time history of the substrate. A range of coatings were
studied; classical intumescents as well as silicate–borate systems. One
salient conclusion was that the binder is critical. Another was that large
expansions are not necessary and can even be detrimental if the char
becomes too frangible. The utility of the frontal model was confirmed.
A related study confirmed the utility of the thin zone model, and
mathematical transforms reduced the model to one which was easily
amenable to numerical analysis. It was shown that although endother-
micity of the foaming process is helpful, it is not essential and the model
fits well to experiment if adiabatic ‘tumescence’ is assumed [22]. A later
modeling study [23] assumed the intumescent reaction to be analogous
to a phase change process occurring over a finite temperature range and
experiment showed that the substrate temperature could be accurately
predicted by suitable choice of latent heat and temperature range for the
intumescent reaction. The model of reference [22] can be taken as a
special case of the later [23] model.
A subsequent Russian study [24] takes more account of the
local viscoelastic properties of the foaming mass, heat conductivity, and
the chemical kinetics. Using a new mathematical algorithm developed by
these workers, a better fit was obtained of the computed data to the
experimental data on a boron-containing intumescent phenol–formalde-
hyde coating. New observations on the morphology of the foam also
provided insights into the details of the intumescent process.
Basic studies in Russia have also been done on particular features of
intumescence. The effects of viscosity and surface tension, and of the
dispersity of solid particles have been examined [25], and the
combustion characteristics of the char were also studied [26].
The effect of a surface coating of polytetrafluoroethylene on an
otherwise intumescent coating was shown, interestingly, to prevent or
retard the intumescence but nevertheless a heat-protective char coating
was formed [27].
A detailed comparison and modeling by Koo [28] of the fire-protective
properties of two commercial intumescent coatings led to the conclusion
that the better performing material had larger expansion and no
contraction as well as lower thermal conductivity.
264 E. D. WEIL
A two-dimensional model was developed in an Australian engineering
school [29] for studying the heat transfer through epoxy subliming
and intumescing coatings. Two different commercial coatings were
evaluated in regard to temperature and surface profiles under flaming
conditions and found to fit well to the model provided that
delamination did not occur. A later model by the same researchers
[30] incorporated kinetic equations and produced a good fit of
conversion under isothermal conditions, except during initial stages of
intumescence and sublimation. Further refinement of the model [31]
showed that atmospheric oxygen content is a major factor.
A generalized pyrolysis model was developed more recently at
Berkeley [32] which can cover a charring (wood) substrate, a non-
charring poly(methyl methacrylate) substrate, and intumescent coat-
ings, and has an encouraging correlation to experimental data.
A model for the intumescence process with ammonium polyphosphate
(APP) and pentaerythritol in polypropylene (not specifically a
coating) was developed by Lille researchers [33] taking into account
kinetics and phase changes. Reasonable correspondence of computer
and experimental temperature profiles lend support to the
model. Intumescence was shown to occur mainly between 2808C
and 3508C, and then degradation of the intumesced coating between
3508C and 4308C by the further action of the flame. Above 4308C,
structural changes occurred in the char. Further modeling by this
group [34] took account of anisotropy from the presence of carbon
nanotubes, non-woven fabrics, and intumescent paint on steel, using
the modeling and simulation heat transfer module of a particular
software package. A further study by this group [35] was directed
toward a broader elucidation of the mechanism of action of intumescent
coatings.
A mathematical model designed to be applicable to systems for
protecting against fast violent heating and explosions as encountered in
military situations was developed in France [36]. It showed promise but
was said to need further studies to improve accuracy.
A study published in 2009 discussed the effects of partial fire
protection on temperature development in steel joints protected by
intumescent coating [37].
Heat Transfer and Combustion Kinetics of a Non-phosphorus
Intumescent System
An intumescent fire-resistance coating for steel based on polychlor-
oprene, ATH, and expansible graphite was studied and shown to
Fire-Protective and Flame-Retardant Coatings 265
undergo three consecutive first-order steps on heating to 873 K – release
of water from ATH, release of hydrogen chloride, and release of gases
from the graphite expansion [38]. All these processes retarded the
heating of the steel substrate.
Optimization Studies of the Ingredient Ratio of APP Systems
In a Russian study, the optimum weight ratio of APP (or some
melamine organophosphonate salts) and polyol for both thermal
protection and oxygen index was found to be 7 : 3 for pentaerythritol,
glycerol, and PVA [39].
An intricate optimization study involving computation as well as
experiment was published by Horacek [40] in 2009 in which he
postulated, and in some cases supported experimentally, a number of
plausible stoichiometric relationships of APP, polyol, and melamine, and
titanium dioxide as well as heat of combustion relationships. The
methodology is intricate and cannot be easily summarized but the
conclusion was that a lower temperature-reacting polyol would be
advantageous; glycerol used along with the pentaerythritol was said to
improve the performance, allowing lower temperature (3008C) for
maximum expansion whereas with the pentaerythritols, maximum
expansion required 3908C. The implication was that the required dry
film thickness and number of coats could be reduced.
Mechanical Strength of Intumescent Chars
The mechanical stability (measured work required to crush the char
from a urea–formaldehyde intumescent formulation) was also found at
the optimum APP-to-polyol ratio, but (not surprisingly) a more
expanded foamed char was easier to crush. The mechanical strength
of various types of chars in the hot and cold states was investigated by a
Russian group [41,42]. The technique used a controllable crushing
device developed for food (presumably baked goods) testing. In a further
study by this group, mathematical modeling was done on the char
formation; smaller pores were found to be beneficial to mechanical
stability [43]. A mathematical model of the bubble phenomena was
developed by these researchers [44]. Radiant heat within the bubbles
was shown to be the main mode of heat transfer [45]. An apparently
more predictive algorithm for modeling the intumescence process was
developed by a Russian–Kazakh group taking account of the local
change of viscosity (found from viscosity isotherms) which affects local
expansion [24].
266 E. D. WEIL
A systematic study at the University of Lille (2006) [46] used
thermogravimetric analysis (TGA), rheometry, and mechanical strength
testing, with statistical methodology, to address the problem of
balancing the desirable expansion with the desirable strength of the
intumesced foam. The results correlated well with industrial furnace
tests. A more recent study by the same group [47] of the kinetics of
pyrolysis led to development of a predictive model for the degradation at
different heating rates.
ADJUVANTS IN INTUMESCENT SYSTEMS – ACADEMIC AND
OTHER BASIC STUDIES
Much development of such systems has been outside of the coatings
field and rather, directed to thermoprocessed polymer systems such as
wire and cable jackets, building materials, and automotive or aerospace
plastics. Nevertheless, it is quite likely that non-coating findings may be
applicable to coatings and, at the risk of some overlap with our previous
review [5] and book chapter [1] on polyolefins, this review will
encompass them.
Researchers at Lille (France) found that zeolites such as 4A (Na A
zeolite) has a very strong synergistic effect in a classical APP/
pentaerythritol intumescent system in polyethylene. The zeolite
encourages formation and stabilization of ‘phosphocarbonaceous’
structures giving an improved intumescent shield, which also decreases
the fuel feeding the flame [48]. The same researchers found a very
helpful effect of including polyamide-6 in an intumescent APP/ethylene–
vinyl acetate system, where the polyamide-6 and APP interacted to form
a second heat-protective shield in addition to that formed from the
ethylene–vinyl acetate APP interaction [49].
Although not explicitly on coatings, a relevant study was done in
polypropylene by University of Turin researchers in collaboration with
Himont researchers [50] on the effect of a series of inorganic fillers in an
APP–aminoplast resin intumescent system. Calcium phosphate, being
unreactive, was found not to spoil the flame-retardant action, whereas
talc and calcium carbonate, which modified the chemistry of the system,
were deleterious. A layer of polyphosphoric acid on the char surface was
beneficial to its insulating action. The heat reflectance characteristics of
the char were also shown to be of importance.
A subsequent study at Hoechst Celanese [51] also done in molded
polypropylene, compared and interpreted the effects of several inorganic
additives on char formation in an intumescent system based on APP
Fire-Protective and Flame-Retardant Coatings 267
and a char-forming polyol. Targeted features for an optimum char were
dense compact outer crust with no porosity, interior sections with a
highly ordered cellular network, and mass. Tin dioxide was antagonistic
by chemical interaction without bridging of polyphosphate, causing
porous flaky char, whereas TiO
2
was beneficial, attributed to bridging of
the polyphosphate.
A research group at a Polish institute [52] recently claimed a
beneficial performance effect in APP-based intumescent coatings by
addition of 0.2–5% nano-scale silica and also by addition of a
hydrophilicizing surfactant 2,4,7,9-tetramethyl-5-decin-4,7-diol (Air
Products Surfynol
Õ
104).
Chemistry of the Classical Char-Former, Char-Catalyst,
and Blowing Agent Systems
The general outlines of this intumescent coating chemistry were
described in the classical Vandersall review. In its most general and
oversimplified summary, an acid-generating catalyst, most commonly
APP reacts with a polyol to initiate dehydration to a carbonaceous char,
and a blowing agent such as melamine or an HCl-releasing polymer or
additive generates gas in the molten mass to make a foam which
solidifies from the melt to make a heat- and vapor-transfer barrier.
Subsequently, detailed studies of the chemical steps were made by
Camino’s group in Turin (1984–1990) [53] and by the research group at
University of Lille (2004) [54]. Both groups relied heavily on thermal
analysis and spectroscopic methods. In this review, we will not repeat a
discussion of this readily accessible work, but to address some of the less
obvious features.
The Behavior of APP When Heated
Based on laboratory-scale thermal studies, such as by the Turin
researchers [55], APP loses ammonia along with water, and in several
stages forms a crosslinked polyphosphoric acid. Actually, the thermal
behavior of APP is quite complex and much depends on whether the
ammonia is in any way constrained. With even light constraint, as in a
loosely capped vessel or a polymer matrix, enough ammonia remains
chemically bonded such that in the extreme case, the end product is a
ceramic-like material, phosphorus oxynitride (PON)
x
[56–58]. The
intermediate steps seem not to have been well investigated although
the formation of a P–N bonded glass has been noted when an APP is
held in a melt with a constraint on ammonia loss.
268 E. D. WEIL
Thermal analysis studies by the Turin group [55] and by Taylor and
Sale at Manchester (1992–1993) [59,60] indicate that with release of
ammonia and water from APP, the reaction is complex and involves
competing crosslinking reactions possibly forming P–N–P bonds (P–O–P
bonds should also be considered). In the typical intumescent formula-
tion, APP can react with a phosphorylatable substrate such as
pentaerythritol and with a reactive amine such as melamine.
Melamine can not only be phosphorylated on the NH
2
group but can
also form a melaminium salt structure with any phosphorus acid group
or even merely by displacing ammonia from the ammonium structure.
Thermal analysis shows that melamine phosphates or polyphosphates
are relatively more stable thermally than APP.
Variations on APP
APP is a complicated material, covering a wide range of molecular
weight and having insoluble higher molecular weight versions besides
the water-soluble, low molecular weight form. A review is available from
a leading European manufacturer [61]; in it, X-ray diffraction diagrams
are given for five crystal forms, as well as solubility data on the main
commercial high-molecular weight form II and various coated varieties
of form II. A more recent Japanese study [62] also provides X-ray
diffraction data on the five forms, and indicates methods of preparation;
moreover, the Japanese researchers show that one of the less common
forms (V) may be a better flame retardant than the others, a surprising
result calling for more research.
Commercial forms of APP are several. A water-soluble, low molecular
weight version is used mainly for non-durable cellulosic flame-retardant
textile finishes. A water-insoluble but relatively hydrolysable version,
Phase I, is sometimes used in coatings and particularly in applications
where water resistance is not needed. A higher molecular weight more
water-resistant Phase II APP is preferred for use in coatings. Several
coated Phase II APP are available from Clariant, Budenheim, and Asian
producers, with both hydrophilic and hydrophobic coatings. A surface-
reacted APP where melamine has been used to replace some of the
ammonium cations represents another water-resistant grade, and may
be further coated with an amino resin to give a still more water-resistant
APP, at a higher price.
A Hoechst patent [63] claims that APP of degree of polymerization of
600–800 and NH
4
:P mole ratio of about 1 is best in water-based coating
formulations from the standpoint of low solubility in water and good
dispersability with minimal settling.
Fire-Protective and Flame-Retardant Coatings 269
A Clariant patent [64] claims combinations of APP with melamine
polyphosphate which have improved stability under high humidity
(tropical) conditions, suffering less loss of ammonia. This patent
discloses many diverse formulations with a variety of binders. A similar
object is achieved by including other melamine salts or guanidine salts
as shown in a related Clariant patent [65]. A combination of APP and
dicyandiamide phosphate is proposed in a more recent patent [66] as the
active ingredient in a water-based epoxy intumescent coating for wood.
The Thermal Behavior of Melamine Itself
A typical component of intumescent coatings is melamine, which is
often said to be the blowing agent (the ‘spumific’). Actually, the role of
melamine is complicated, and even the thermal behavior of the material
by itself is complicated, as discussed in our 1995 review [67]. When
heated in a small amount where vapors can escape without constraint,
melamine totally sublimes in the 250–3508C range, as shown by the TGA
curve published by Taylor and Sale [59,60]. However, if the vapors are in
any way constrained as, for instance, by heating of melamine from the
bottom in a deep layer, part of the melamine sublimes and part loses
ammonia and goes through a series of ammonia-losing condensations to
yield –NH– linked two, three, and multiple ring condensation products,
called melam, melem, and melon, respectively. The sublimed melamine
vapors and the released ammonia are poor fuels and probably flame
inhibitors, even though ammonia gas is per se flammable. Melamine
vapor is said to be capable of endothermic dissociation to cyanogens [68],
also a poor fuel; whether that chemistry and heat-sink effect play a role
in the flame-retardant contribution of melamine has not been
established.
It has been found that in intumescent coatings containing melamine,
further addition of a chloroparaffin aids the performance. Lille
researchers [69] found that melamine or its thermal condensation
products (discussed in some detail) caused the dehydrochlorination of
the chloroparaffin and that this was a step in the effective action. It was
further suggested that PVA or polyvinyl acetate could be substituted for
the chloroparaffin.
Interaction of Melamine With Phosphorus Ingredients in
Intumescent Coatings
Obviously, melamine being a base albeit a rather weak one, can react
with phosphorus acid species made available, for example, by
270 E. D. WEIL
decomposition of ammonium phosphate, or it may even displace some
ammonia from the ammonium salt to directly make melamine
phosphate salts.
Melamine phosphate, pyrophosphate and (later), polyphosphate are
all commercially available and they find use in intumescent coatings.
A very thorough 1979 review by Kay et al. [70] covers both the
combinations of melamine with phosphate retardants, their interaction,
and the use of pre-made melamine phosphates. Our later review
(1994) [71] covered the coating applications. Advantages are shown
for melamine pyrophosphate over melamine phosphate in both thermal
barrier formation and lower water solubility. Formulations using
various binders are discussed, and details of representative water-
based formulations are given using vinyl acrylic emulsion and polyvinyl
acetate emulsions with performance information. Formulations using
melamine phosphates and APP together are discussed.
Melamine orthophosphate dehydrates to melamine pyrophosphate
and thence at 2908C and above to melamine polyphosphate. Melamine
polyphosphate can serve as both blowing agent and as a substance (or its
thermolysis products) contributing to the foam layer as a coating
intumesces [72]. Further heating under laboratory conditions at above
6008C can eventually lead to (PNO)
x
, a crosslinked solid, although it has
not been established that this higher temperature chemistry plays a
significant role in intumescent coatings under fire conditions. (PNO)
x
is
probably too stable and infusible for use as the only phosphorus
component in a typical intumescent coating although we found that it
may be effective in systems where it can interact with a polymer such as
a polyamide [73].
Variations of Melamine Phosphate
A hybrid salt composition made by the reaction of phosphoric acid
with melamine and monoammonium phosphate is said in a 1993 patent
[74] to substantially reduce the solubility of ammonium phosphate
while retaining its low thermal dissolution (activation) temperature.
A number of water-based intumescent paint formulations are shown.
Other Phosphorus Compounds in Intumescent Coatings
Chloroalkyl phosphates and phosphonates have been reported as
useful in intumescent coatings, even coatings which also contain
inorganic phosphates such as APP; the organic phosphate or phospho-
nate esters can provide plasticity, better coating properties, and
Fire-Protective and Flame-Retardant Coatings 271
can serve as blowing agents and (by breaking down to phosphorus
acids) charring catalysts. Some formulations disclosed in patents show
use of monophosphates such as tris(2-chloroethyl) phosphate [63].
However, chloroalkyl phosphate and phosphonate oligomers with more
than one phosphorus ester group per molecule such as Phosgard
Õ
C22R or 2XC20 (former Monsanto, now Albemarle) and Fyrol
Õ
99
(former Stauffer, Akzo Nobel and Supresta, now ICL-IP) have generally
been preferred. An early example shows the use of Phosgard
Õ
C22R
or 2XC20 in an epoxy-based intumescent coating which also contained
APP and melamine phosphate or guanylurea phosphate [75]. This
patent, which shows complex formulations, also claims a performance
advantage of having the decomposition temperatures of two of the active
ingredients (either the P or the N component) at least 508C apart.
Substantially, halogen-free systems may use triaryl phosphates such as
isopropylphenyl diphenyl phosphate (ICL-IP’s Phosflex
Õ
31L or a
similar Chemtura Reofos
Õ
) to provide plasticity.
Partial esters of polyols, notably of pentaerythritol and glycerol,
are made by reaction with polyphosphoric acid and subsequently cured
with epoxy resins and melamine formaldehyde resins to make clear
intumescent varnishes on metal, wood, and textiles in a 1995 patent
[76]. Further optimization of the coating properties, such as improved
flexibility, is said to be achieved if a partial phosphate polyol ester made
from tetrahydrofuran or 1,4-butanediol is part of the polyol phosphate
reactant [77]. This patent application has a lengthy discussion of the
history and rationale behind this versatile family of phosphorus-based
intumescent coatings.
Two-component intumescent coatings of the mixed glycerol/pentaer-
ythritol acid phosphate type, cured with aminoplast resins, are said to be
especially suited for flame-retardant coating of fiberglass mats [78].
A patent application of Leigh’s Paints [79] discloses the use of
diglycidyl methylphosphonate, triglycidyl phosphate, bis[2-(methacry-
loyloxy)ethyl] phosphate or dihydroxaphosphaphenanthrene oxide
(DOPO), or preferably an adduct of DOPO with an epoxynovolac, in
intumescent coatings especially for steel.
Char-Producing Ingredients
Many of the older formulations use pentaerythritol as the char former
‘carbonific’ in conjunction with APP as the charring catalyst. However,
it is somewhat water soluble and the less-soluble although more
expensive dipentaerythritol is often preferred. In a published compar-
ison of pentaerythritol to di- and tripentaerythritol using rheological
272 E. D. WEIL
measurements [80], it was found that pentaerythritol was the most
effective in intumescing sooner and keeping the substrate temperature
down longer. On the other hand, the temperature at which embrittle-
ment started was higher for the di- and tripentaerythritol; so, this
feature could be of value in lessening the lack of high wind resistance
and the high-temperature cracking – faults of intumescent coatings,
especially on cylindrical steel columns.
Lower cost cyclic formals (1,3-dioxanes) which are byproducts of
pentaerythritol manufacture have been shown by Perstorp [81] to be
useful as replacements for the pentaerythritols in intumescent coatings.
Another excellent char former is tris(hydroxyethyl) isocyanurate
(THEIC), but this is also water soluble; therefore, polyesters derived
from THEIC are shown as preferred by Hoechst in epoxy-based
coatings [82].
Other ‘carbonific’ (char-forming) additives have been synthesized.
A Chinese university group [83] describes preparation and testing of
an ethanolamine–aminotriazine oligomer in a polyurethane intumescent
coating. The formulation had good rheology and the resultant film had
good thermal stability.
A Polish study [84] was done to arrive at effective intumescent
coatings for wood. In this study, dextrin (a starch product) was part of
the char-forming system, supplementing a urea–dicyandiamide–formal-
dehyde resin catalyzed by APP. Starches, sugars, and cellulose powders
are often mentioned in lists of char-forming ingredients for intumescent
formulations.
The Role of Titanium Dioxide in Intumescent Coatings
TiO
2
is shown in many intumescent formulations. Besides its use as
a white pigment, it is a key reactive in many cases. Commercial
intumescent coatings, when fully expanded, often show a white exterior
of the expanded foam, even though the inner part near the substrate is
dark carbonized material. This white exterior has been identified
analytically [85] as mainly titanium pyrophosphate, formed by the
reaction of APP (probably via phosphoric acids) with TiO
2
. Another
authority [86] proposes that titanium pyrophosphate is formed by
reaction of P
2
O
5
with TiO
2
in the intumescing coating.
An early overview of intumescent fire barriers by a Monsanto
researcher, Ellard [87] emphasized the importance of formation of a
glassy outer barrier layer, preferably with a high reflectance, and the
role of inorganic oxides (Ti, Zr, and Sb) and phosphates in producing
such a layer.
Fire-Protective and Flame-Retardant Coatings 273
Intumescent Silicate Coatings
Water-soluble silicates have a long history of use as wood coating
and impregnants. Because of their water content, and ability to
melt, they tend to be fairly intumescent. They can be produced as
intumescent powders and formulated in a binder for use as metal-
protective coatings. An improved product of this sort with an
intumescent temperature above 1958C, suitable for coatings or firestops
uses a lithium–sodium–potassium silicate composition [88]. Another
improvement on the alkali silicate coating is the incorporation of up to
5% sodium phosphate which allows for improved high temperature
resistance such as at 9058C as needed in fuel fires [89]. Encouraging
results were obtained with an intumescent inorganic silicate coating
applied on a glass-reinforced polyester with a glass mat as intermediate
layer; the ASTM E162 test for surface flammability was passed as well
as a US Navy quarter-scale flashover test [90].
An intumescent powder blend was patented by Alcoa [91] comprising a
fibrous (preferably vitreous) calcium magnesium silicate, used in a coating
or mastic with a binder such as an acrylic resin or polyvinyl acetate.
An intumescent caulk or firestop can be prepared using 3M’s
Expantrol
Õ
4BW, a hydrated sodium silicate–borate in a formulation
containing an acrylate–vinyl acetate–ethylene terpolymer, an organic
phosphate plasticizer, zinc borate, a polyol and glass fiber [92].
Patents on Improvements in Intumescent Coatings by
Boron-Containing Additives
An early patent [93] on epoxy-based intumescent coatings for wood or
steel beams uses a melamine phosphate combination with melamine
borate (optimum 7 : 3) to extend the protective time in a fire.
A fire-protective intumescent coating for steel is claimed [94] using a
water-soluble sodium silicate, borax, ATH, and kaolin. Formation of a
vitreous thermal barrier is shown to occur.
Boric acid is a component of a complex epoxy mastic [95] which also
contains APP, a triaryl phosphate, THEIC, silica, perlite, and ceramic
fibers. This was commercialized as a coating for protection of steel from
hydrocarbon fires.
A French research group [96] showed that including boric acid in an
APP–epoxy-based intumescent coating on steel gave not only longer
thermal protection (highest expansion) but also better adhesion and
better mechanical resistance. Reaction of the boric acid with the
phosphate to form a borophosphate was shown [97].
274 E. D. WEIL
Zinc borate, or at least a combination of zinc oxide and a borate, is
claimed to improve the thermal protection of steel provided by an
intumescent coating which contains the usual APP and melamine, in a
rather flexible cured epoxy matrix [98]. An overview of the applications
and performance of these polypropylene glycol (PPG) coatings on steel,
particularly for offshore oil platforms, has been published [99].
Patents on Improvements in Intumescent Coatings by Other
Inorganic Additives
Intumescent coatings based on the APP–char former–blowing agent–
glass fiber combinations are made more protective at high temperatures
by inclusion of Ti or Zr or other metal borides, nitrides, or carbides [100].
Refractory fibers, such as alumina- or silica-based fibers, are added to
improve the high-temperature performance and long duration protection
given by a complex intumescent formulation on wood or metal [101].
Intumescent coatings suitable for protecting steel against high-
temperature (fuel) fires are enhanced by inclusion of sodium potassium
aluminum silicate (nepheline syenite) or potassium aluminum silicate
[102]. Synthetic glasses have been shown to enhance intumescent
coatings [103].
A university study [104] compared a number of commercially
available high-temperature ceramic fibers and some minerals incorpo-
rated into an epoxy and a water-based intumescent systems.
Carborundum’s Fiberfrax
Õ
HS-70C (an alumina–silica fiber with other
components) and Zicar
Õ
ALBF-1 (an alumina fiber) were found to
enhance the toughness of the residual char.
Much effort has been expended on improving fire-resistant coatings
by addition of nanoclays and other nano-dimensional inorganic fillers.
A brief review of fire-retardant nanocomposite coatings by Koo and
Pilato [105] is in a 2006 book. A study on wood-protective intumescent
coatings at the National Institute of Standards joint with Polish
researchers [106] showed that the level of flame-retardant additive
needed in a butyl acrylate based formulation could be reduced by
incorporating some organically modified montmorillonite clay, while
maintaining fire properties as determined by cone calorimeter. Studies
in China [107] showed that adding up to 1.5% phyllosilicate clay or
layered double hydroxides (both having layers of nanometer thickness)
improved the thermal shielding by the char layer. In an overview by
Turin Polytechnic investigators [108], nano-scale additives were
proposed (with limited data, mainly on phyllosilicate clays) to give fire
protection benefits in intumescent paints; additives specified were
Fire-Protective and Flame-Retardant Coatings 275
montmorillonite, hectorite, saponite, double-layer MgAl hydroxides,
zirconium phosphate, carbon nanotubes, nanosilica, nanotitania,
nanoalumina, fullerenes, and silsesquioxanes. Exfoliated montmorillo-
nite clay was shown by Hu and Koo [109] to have a synergistic effect in a
conventional intumescent wood coating.
Chinese studies [110] showed that about 4% of nanometer silica or
magnesium hydroxide, surface modified by Solsperse
Õ
17000, can
improve the water resistance of APP–pentaerythritol–melamine coat-
ings without harming flame retardancy.
Catalysts to Improve Intumescent Formulations
The addition of certain spirobis amines (example: 2,4,8,10-tetraox-
aspiro-5,5-undecane-3,9-dipropamine) and quaternary phase transfer
catalysts (example: tetrabutylammonium salts) are shown to improve
the performance of intumescent systems based on APP, melamine
phosphate or ethylenediamine phosphate [111]. The working examples
are in non-coating systems.
Patents on Expandable Graphite in Intumescent Coatings
Citations in recent patents provide a history of the use of
heat-expandable acid-treated graphite flakes to boost the fire-barrier
properties of various types of intumescent coatings. A representative
patent by Huber inventors shows use of expandable graphite plus an
acid-capturing additive such as calcium carbonate to enhance a typical
intumescent system for wood [112]. The combined use of expandable
graphite with glass or ceramic microballoons is shown in an otherwise-
typical intumescent coating for building components such as steel
conduits [113]. Another Avtec patent [114] shows use of expandable
graphite together with a cement and a ceramic in a smoke- and fire-
resistant coating with typical intumescent components. The use of
expandable graphite in an acid-hardenable resin coating is shown for use
on oriented strand board, fiberboard or glass-reinforced sandwich panels
in a Georgia-Pacific Resins patent (2001) [115].
Binders for Intumescent Coatings
A variety of polymeric binders have been used. In water-based
intumescent coatings, a polyvinyl acetate emulsion is often chosen, and
it is believed to also contribute to the char.
276 E. D. WEIL
In a comparison of various binders for a conventional APP–melamine–
pentaerythritol formulation, chlorinated rubber blended with chloro-
paraffin gave high performance and withstood aging [116]. The use
of a low modulus rubber with a similar intumescent formulation for
steel coating has been claimed in a patent disclosure by British
inventors [117].
In an Eliokem patent application [118], it is shown that a combina-
tion of a linear and a crosslinked (reticulated) methylstyrene–
acrylic copolymer not only reduces flame spread in the early stages
of a fire but also improves the char formation and insulating
properties of the char in the later stages of a fire. Eliokem researchers
[119] have discussed the systematic development of optimized
substituted styrene–acrylate latexes for fire-resistant coatings.
Better water resistance compared to vinyl acetate copolymers is
shown. A study at Eliokem indicated optimum thermal stability
of protective coatings for metals by combining 2-ethylhexyl acrylate-
p-methylstyrene linear and reticulate copolymers [120,121]. The
Eliokem styrene (or vinyltoluene)–acrylate copolymer resins, sold as
Pliolites
Õ
, are used in Leighs Paints solvent-based intumescent coatings
on steel, for example protecting the large steel structure of the
Wimbledon tennis courts (2009 report). Studies at Eliokem have
elucidated the relative efficiency of various thin film intumescent
coatings [122].
A polymerizable resin approach is shown in a W. & J.
Leigh patent [123] which discloses a classical APP–pentaerythritol–
melamine intumescent formulation with a polymerizable acrylic
resin plus preferably a preformed meth(acrylate) polymer plus a
free-radical polymerization initiator such as benzoyl peroxide.
This provides a liquid formulation which cures to a solid on a
substrate such as steel. A related patent [124] uses a similar liquid
composition with a reinforcement structure such as fiberglass or steel
mesh.
Solid intumescent formulations suitable for powder coatings
are described in a Leigh patent [125] and a wide variety of thermoplastic
and thermosetting binders, including polyethylene, are said to be useful
but the working examples use a thermoplastic polyetheramine,
Dow Blox
Õ
2100.
Improvement in adhesion of intumescent coatings to metal is claimed
to result from including in an acrylic binder formulation a copolymeriz-
able acid monomer, namely, an acid (meth)acrylate, maleic, fumaric, or
itaconic acid [126].
Fire-Protective and Flame-Retardant Coatings 277
Epoxy-Based Intumescent Coatings and Mastics for
Steel Protection
Present-day formulations can be rather complex, particularly those
used for their intumescent thick coatings (mastic) such as employed for
protection of off-shore oil drilling platforms and petrochemical
installations.
Examples of such advanced and proprietary formulations are Textron’s
(now Akzo Nobel’s) Chartek
Õ
and PPG’s Pittchar
Õ
. An example
of a Pittchar
Õ
formulation is disclosed in a PPG patent [127]. The
formulation is as follows (component; parts by weight): Package 1:
diglycidyl ether of bisphenol-A, 35.77; melamine, 2.75; APP, 4.52; tall oil
fatty acid, 4.27; tris(2-chloroethyl) phosphate, 8.79; attapulgite gellant,
3.31; boric acid 20.64; zinc borate, 7.87; wollastonite, 12.05. Package 2:
Versamid
Õ
150 curing agent, 72.25; Aerosil
Õ
vapor-phase-produced
silica, 3.50; Iimsil
Õ
A-10 silica, 13.72; attapulgite gellant, 4.50; talc, 6.00.
Packages 1 and 2 are mixed in 1.65 weight ratio before applying. This
coating is applied in a thick layer as a mastic. A more flexible epoxy
coating with many of the same ingredients but with a polyester-chain-
extended epoxy has been described in later PPG patents [128,129].
An interesting intumescent coating for steel has recently been
patented and probably commercialized by Chance & Hunt Ltd and
Ferro Ltd [130], wherein a combination of an epoxy resin with an
aldehyde resin or ketone thermoplastic resin serving as part of the
binder and as the ‘carbonific’ (char-forming) component. The formula-
tion is: 18% epoxy resin, 6% phenolic curing agent, 10% ketone resin
(such as BASF’s Laropal
Õ
A81), 3.5% % hydrogenated castor oil viscosity
modifier (such as Rheox’s Thixcin
Õ
), 55% APP (such as Exolit
Õ
422),
and 7.5% TiO
2
.
A low-density epoxy-based intumescent coating, Chartek
Õ
VII, is
described in a Textron patent [131]. The composition, which must be
mixed in a very specific sequence and manner, is quite complex, as
presented in Table 1. Each of the two parts is mixed before applying:
by spray equipment
The density of this coating can be further reduced by pressurizing and
dispersing a gas in it before applying. This recipe suggests that
sophisticated formulation development is needed to achieve competitive
products in the flame-retardant coatings field.
Recent intumescent coatings with lengthened fire resistance have
made use of the very active dialkylphosphinate aluminum salt as part
of the flame-retardant composition [132]. A representative formulation
used 25 parts of boric acid, 9 parts of THEIC, 2 parts of TiO
2
, and 5 parts
278 E. D. WEIL
of a mixture of APP and aluminum diethylphosphinate (Exolit
Õ
OP1230) in 100 parts of epoxy resin (Beckopox
Õ
EP140) cured with
an aliphatic polyamine. Cured on steel at 3.5 mm, this coating gave
44 min of fire resistance.
Special Applications of Intumescent Coatings
Multi-layered structures can be used to give a high degree of fire
protection to steel structural elements; one patent [133] indicates that
an outer layer can be fiberglass with an intumescent coating, on top of a
reflective metal foil, on top of a low conductivity refractory-fiber blanket,
on top of another reflective metal foil layer. A similar multi-layer
construction can be used to protect conduits and cables [134]. The No
Fire technology also has found application in passenger aircraft.
The multi-layer concept was applied differently in a patent to Battelle
inventors [135]. Here, the idea is to apply a first intumescent coating
layer on the substrate, then on top of that, another intumescent coating
which forms a less dense layer of foam when exposed to fire, the outer
Table 1. Intumescent low-density epoxy coating (mastic) formulation.
Ingredient Weight (lbs)
Part A
Epoxy resin (Dow DER 331) 1702.8
Triaryl phosphate 438.3
Black pigment 4.5
Antifoaming siloxane surfactant 0.45
Amorphous hydrophobic fumed silica 67.5
Fire-retardant mix (64% APP (Exolit
Õ
422) and 36% THEIC) 675
Boric acid 1521.4
Expanded perlite 45
Amorphous mineral fiber (Inorphil
Õ
) 22.5
High-surface area Al
2
O
3
/SiO
2
fiber (HSA fiber, Unifrax
Õ
) 22.5
Part B
Amidoamine curing agent 2554
Wetting agent 10
Antifoaming surfactant 0.4
Milled limestone 401.2
Fire-retardant mix (64% APP (Exolit
Õ
422) and 36% THEIC) 461.6
Rutile TiO
2
pigment 76.8
Perlite 224
Amorphous mineral fiber (Inorphil
Õ
) 148.4
High-surface area Al
2
O
3
/SiO
2
fiber (HSA fiber, Unifrax
Õ
) 123.6
Fire-Protective and Flame-Retardant Coatings 279
layer giving the immediate fire protection and the inner harder layer
providing a second layer of defense in case breakthrough of the outer
intumesced layer occurs. The outer layer formulation is based on APP,
dipentaerythritol, and epoxy with an azobiscarbonamide blowing agent.
The use of intumescent coatings on plastics, such as plastic pipe, is
disclosed in a Monsanto Europe patent [136]. These coatings, however,
are not paints or mastics but appear to be extruded or laminated, and
have a substantial thermoplastic, possibly foamed thermoplastic,
content.
Thin intumescent coatings on wire and cable, applied by melt
extrusion, are described in a patent application of Reyes [137] using
formulations in a polyolefin including melamine phosphate, ethylene-
diamine phosphate, and activators of the pentaerythritol spirobisacetal,
and quaternary ammonium types as mentioned earlier in connection
with a Rhodes et al. [111] patent.
Polyurethane foams used in thermal insulation can be made fire-
resistant by an intumescent coating, preferably applied by spraying, as
described in a patent application [138]. Another coating for the same
purpose is a water-based Flame Seal
Õ
-TB Spray-Applied Thermal
Barrier from Specialty Products, Inc. [139]. Further foamed coatings
applicable to thermal insulation for fire, sound, and heat barriers
purposed are described by Lanxess [140].
Patented combinations of intumescent paints (such as based on APP,
pentaerythritol and melamine, and latex binder) with mold inhibitors
and insecticides (particularly termiticides) have been disclosed
[141,142]. These may be applied to any substrate for fire, mold, and
insect (termite) protection.
Intumescent Coatings on Textiles
These coatings are usually applied to the surface as a layer. Products
from Thor (France) used in this way are Aflamman
Õ
PCS and
Aflamman
Õ
IST (water-soluble organic–inorganic phosphorus nitrogen
combination), applied with a polyvinyl acetate emulsion binder
Rhenappret
Õ
RA. A French study shows that this finish on polyester
fabric lengthens the time to ignition and shortens the time to extinction,
and can provide a French M1 (non-flammable) rating [143].
Improved fire-protective performance on substrates such as, particu-
larly, textiles is claimed for intumescent coating formulations containing
APP, pentaerythritol, and melamine with specific latex polymers
(styrene–acrylate–methylenebisacrylamide copolymers exemplified)
having a thermogravimetric weight loss of at least 7% at 3708C [144].
280 E. D. WEIL
Improved thermal and warm water resistance properties of coated
textiles such as car interior fabrics are said to be achieved by use, in
place of APP, of a melamine phosphate coated with a functional
organosilicon resin [145]. An extensive university study of phosphorus-
containing flame retardants in backcoating of textiles was conducted in
the UK [146]. These formulations are not necessarily intumescent ones.
Silicone Coatings
Silicone coatings with dispersed carbon nanotubes have been
introduced as Nanocyl’s ThermoCyl
Õ
to give fire protection to a wide
variety of substrates, such as plastics, cables, textiles, foams, metals, and
wood [147]. Coatings as thin as 100 mm have been shown effective. These
do not appear to be intumescent coatings.
Very High-Temperature Ceramic Coatings
Coatings such as Al
2
O
3
–TiO
2
, ZrO
2
, and other ceramic thermal
barrier coatings are used, for example in aerospace, electronic and
biomedical applications, and may be applied usually to metal substrates
by plasma/high-velocity oxygen flame spraying. Further discussion is
outside the scope of this review and the reader is directed to the annual
proceedings of the International Thermal Spray Conference. Slurry
methods of application of ceramic coatings are also used to provide
metals with short-term exposure to high temperatures, and have been
reviewed [148].
Aerospace tiles, which are inherently fire resistant, can be coated with
further heat-resistant coatings such as a recently disclosed system of
ceramic/metal nanoparticles [149].
Ceramicizable compositions, suitable for cable coatings and seals,
have been developed by an Australian group [150] on the basis of a
silicone polymer, mica, and a combination of a low melting glass and a
high melting glass. These inorganic materials flux to form a self-
supporting protective ceramic coating after the organic component has
burned away. The same research group discloses a related ceramifying
coating material, suitable for protecting cables at high temperature,
using an inorganic phosphate, which is exemplified by APP, as part of
the ceramifying system along with a mineral silicate exemplified by talc,
mica, or clay [151]. A discussion of the science and technology of this
approach has been published by the Australian researchers [152].
Australian researchers [153] described a basic study which led to
ceramifying compositions based on polyvinyl acetate, kaolin or talc,
Fire-Protective and Flame-Retardant Coatings 281
magnesium hydroxide, and zinc borate (as flux). Kaolin provided
stronger ceramic but talc provided a better thermal barrier for firestop
applications.
Intumescent Coatings on Reinforced Thermoset Composites
An extensive study of intumescent coatings for shipboard use, using
small-scale and full-scale fire, adhesion and impact tests, by the US Navy
[154] showed failure to meet Navy criteria when used as stand-alone
coatings on reinforced thermoset composites. Many of the coatings
demonstrated poor adhesion during fire tests. However, some did reduce
flame spread and smoke generation when applied over reinforced plastic,
and one which contained a mineral adjuvant performed well in
combination with StructoGard
Õ
(a mineral blanket).
Testing of Fire-Protection Coatings
A succinct review of tests for fire-protective coatings, especially for
steel, is found in a 2002 BCC paper [155].
Typical large-scale tests in the USA are the ASTM E-84 (Steiner
tunnel) for flame spread and the ASTM E119 for fire resistance. There
are also UL 1709 or ASTM E1529 for protection time in a rapid
temperature rise fire, such as the one which may occur in an offshore oil
or gas platform. Both UL 1709 and ASTM E1529 require a test furnace
which develops an average temperature of 20008F (10938C) in the first
5 min. The principal difference is that the UL 1709 involves a total heat
flux somewhat larger than that in ASTM E1529. These are all quite
large tests with specially dedicated equipment. The test method, ASTM
E119 (also UL 263 and the similar ISO 834 used elsewhere in the world),
involves a large test rig, has been used for decades and is still used to
measure the fire performance in a solid fuel fire (‘cellulosic’ type fire), of
walls, doors and floors. For combustible construction materials such as
wood, the ASTM E-84 is commonly used to measure the effectiveness of
coatings to retard flame spread. However, this test requires large
samples and is relatively costly. A useful ability to predict E-84 results
on coated wood was demonstrated using small-scale tests in the cone
calorimeter Koo’s group [156].
Standards and tests relating to civilian shipboard fire protection are
under the SOLAS Codes of the International Maritime Organization and
in the USA, administered by the Coast Guard. An overview of the
standards going into effect in 2003, and systems for meeting these
standards, was presented in 2002 [157].
282 E. D. WEIL
From a research standpoint, a faster and convenient small-scale
screening test was developed at Lille [158]. This test involves using a
small radiant heater (the French epiradiateur, directed downward on a
5 5cm
2
plate painted with the test coating. An infrared thermometer is
used to read the bottom temperature of the plate. Even more informal
tests of this sort are sometimes run for purposes of formulation
development, using a propane torch held at a fixed distance from the
coated plate.
British standards for fire-protective coatings are discussed and
illustrated in a 1983 review which covers in special detail the railway
requirements and experience [159]. A major standard for fire protection
of building materials has been BS 476, part 21. This has been replaced
by the CEN standards of the European Union and the related ISO 834
standard elsewhere.
Firestops
In a building, penetrations through fire-rated walls and floors/ceilings
for pipes, ducts, cables, wires, conduits, and structural members
provide dangerous pathways for fires and fire gases to spread.
In recent years, building officials and fire marshals have begun to
prioritize firestopping barriers in building codes. In the USA, fire-
stopping should use products tested and approved under ASTM E 814,
a test with a specified flame at one side of the aperture, and means
for measuring temperature on the other side. Time for no passage
and time to reach 400F are measured, as well as air leakage. Resistance
to a hose stream is also evaluated.
Much of the patent literature on firestops emphasizes the mechanical
aspects such as shaping to fit various apertures, the use of shields and
supports, putty-like materials, and combinations with aperture blocking
means such as mineral wool. We will cite some representative patents of
leading firestop manufacturers which emphasize the compositional
aspects, often complex, and often proprietary.
A flexible felt containing an intumescent material was patented by
3M [160], the composition comprising an acrylic latex, a phosphate
plasticizer, an APP, an acid-treated expandable graphite, ATH, sodium
aluminate, aluminum sulfate, and various surfactants applied to a mix
of ceramic fibers and rayon fibers, and compressed to a fire-barrier felt.
A more recent solid fire sealing material patented by 3M [161]
comprises a dried rubber latex, TiO
2
, APP, a phosphate plasticizer, 3M’s
Expantrol
Õ
(a granulated hydrated sodium silicate), and various
stabilizers. A firestop putty, also patented by 3M [162] contains a mix
Fire-Protective and Flame-Retardant Coatings 283
of rubbers, epoxy resin powder, silica, melamine, boron oxide, fiberglass,
a liquid olefin copolymer, and Expantrol
Õ
or expandable graphite.
A version of expandable graphite said to be advantageous as a firestop
ingredient because of reduced onset temperature and higher expansion
is patented by Hilti [163] and it uses nitroalkane and ferric chloride for
intercalation of the graphite. Another Hilti patent [164] describes a
complex formulation for a two-component intumescing foam comprising
specific polyurethane foam-forming ingredients, APP, tris(chloroisopro-
pyl) phosphate, dipentaerythritol, melamine cyanurate, zinc borate, iron
oxide, silica, expandable graphite, and urethane catalysts; this formula-
tion is injectable into wall apertures as a firestop.
Flexible intumescent sheets, suitable for firestops in the gap between
door and doorframe, were patented by Rectorseal [165] which comprise
expandable graphite, ethylenediamine phosphate (an intumescing salt),
and a soft emulsion resin.
A two-stage expandable firestop was patented by Specified
Technologies [166] which makes use of a two-stage expansion: the
lower temperature expansion uses microcapsules with polyvinylidene
chloride walls filled with liquid isobutene and the higher temperature
expansion uses expandable graphite, both in an acrylic latex. A related
firestop system [167] uses expandable graphite plus alkane-filled
microcapsules (Akzo-Nobel Expancel
Õ
) or a nitrogen- or CO
2
-releasing
blowing agent, plus, as a supplemental flame retardant, a phosphate,
borate, or clay.
FLAME-RETARDANT GELCOATS
These are coatings made from curable unsaturated polyester resins
and cured in place, typically onto a glass-reinforced polyester laminate.
They are often in the range 0.4–0.5 mm, and provide a smooth surface to
the laminate. Unlike paints, they may be applied as an early stage of
laminate production, such as in the mold. Typical formulations are
similar to regular unsaturated polyester resins, and with similar curing
catalysts (usually peroxides) but with thixotropic agents added to
control rheology. Flame retardancy requirements for gelcoated compo-
sites are often found in railway, construction, and marine applications.
A new railway requirement in Europe is the EN 45545 standard which
involves a flame spread test, as discussed in a recent Cytec paper [168].
Intumescent formulations such as based on APP, pentaerythritol and
melamine may be used. ATH may also be used but high loadings have
viscosity problems. A UK article [169] discusses the trade-off between
284 E. D. WEIL
weatherability and flame spread, and the choice of putting the flame
retardant in the gelcoat or in the base laminate. A recent article from
Clariant [170] shows that the British rail standard 476 can be passed by
using 50 phr of Exolit
Õ
AP 740 (an APP plus a char former) in a gelcoat
plus 50 phr ATH in the laminate or 100 phr Exolit
Õ
AP 740 in the
gelcoat and none in the laminate. This second option is especially useful
for the resin transfer molding process.
CONCLUSIONS AND FUTURE DEVELOPMENTS
Effective products have evolved to meet fire protection requirements
on steel, wood, and to some extent on plastic or elastomer substrates.
Depending on composition and thickness, protection can be offered
against both lower energy ‘cellulosic’ fires and high-energy ‘hydro-
carbon’ fires.
Demanding new standards for fire testing, test standardization, and
product classification, such as ENV 13381 and EN 13501 may drive the
development of improved intumescent and other types of fire-protective
coatings, predicted by European coatings workers [171]. In the USA,
wider adoption of the ICC building codes continues, and some of the
requirements can be met most economically by fire-resistant coatings.
Environmental considerations, particularly strict solvent limitations to
limit air pollution, strongly favor water-based or high-solid coatings.
Some shortcomings still need to be met by further research and
development. Weathering of exterior intumescent coatings has usually
been inadequate because of hydrophilic components. Protective top
coatings can be used, but add to cost. A recent patent application claims
that the inclusion of a highly water-resistant resin component,
exemplified by a polyvinylidene fluoride emulsion such as Arkema’s
Kynar
Õ
Aquatec, in an otherwise typically hydrophilic intumescent
formulation improves water resistance [172] and may avoid the need for
a protective topcoat.
Adhesion of fire-resistive coatings to substrates, particularly steel,
may require a primer coat, but this also may be avoidable by self-priming
formulations. Adhesion to plastic or elastomer surfaces presents an
R&D opportunity. Single coating applications have obvious cost
advantages.
A shortcoming of some protective intumescent coatings on steel
columns is the tendency to crack open at the full extent of their
expansion, thus exposing the substrate to the flames. A recent patent
application by a Japanese company (2010) [173] indicates an
Fire-Protective and Flame-Retardant Coatings 285
APP–pentaerythritol–melamine formulation in which the cracking
propensity has been controlled by including rockwool fibers.
REFERENCES
1. Weil, E. and Levchik, S. (2009). Flame Retardants for Plastics and Textiles:
Practical Applications , Hanser Publishers, Munich/Cincinnati, OH.
2. White, R.H. and Dietenberger, M.A. (2010). Fire Safety of Wood
Construction, In: Wood Handbook, Chapter 18, pp. 18–1ff, Forest
Products Laboratory, US Department of Agriculture, Madison, WI.
General Technical Report FPL-GTR-190.
3. Heemstra, D. (2009). Intumescent Fireproof Coatings: Their Uses and
Applications. Available at: http://www.corrdefense.org/Academia%20Govern
ment%20and%20Industry/T-01.pdf (accessed date December 28, 2010).
4. Vandersall, H.L. (1971). Intumescent Coating Systems, Their Development
and Chemistry, Journal of Fire and Flammability, 2: 97–140.
5. Weil, E.D. and Levchik, S.V. (2008). Flame Retardants in Commercial Use
or Development, Journal of Fire Sciences, 26: 5–43.
6. Schwarz, R. (2003). Coatings that can Save Lives, Coatings World,
Nov. 2003: 54–59.
7. Allen, C. (1999). Choosing the Right Fireproofing for Structures and
Equipment Supports, Chemical Engineering Progress, 95: 75–80.
8. Goode, M., ed. (2004). Fire Protection of Structural Steel in High-Rise
Buildings, GCR 04-872, Building and Fire Research Laboratory, NIST,
Gaithersburg, MD.
9. Challener, C. (2007). Fire Safety with Specialty Coatings, JCT Coatings
Tech, Sep. 2007: 78–84.
10. Green, J. (2005). Fire-Retardant/Fire-Resistive Coatings, In: Tracton, A.
(ed.), Coating Technology Handbook, 3rd edn, pp. 773–778, CRC Press,
Boca Raton, FL.
11. Dahm, D.B. (1996). Reformulation of Fire Retardant Coatings, Progress in
Organic Coatings, 29: 61–71.
12. www.nstcenter.com/milspecs.aspx?milspec¼24647 (accessed date December
28, 2010).
13. Calbo, L., ed. (1992). Handbook of Coatings Additives, Vol. 2, p. 261, Marcel
Dekker, Inc., New York, NY.
14. Spain, R. (1987). US Patent No. 4,666,960.
15. Kruse, D., Simon, S., Menke, K., Friebel, S. and Gettwert, V.
(to Fraunhofer–Gesellschaft zur Fordering der angewandten Forschung)
(2005). German Patent Application No. 10 2004 023 166.
16. Ray, N., Shaw, B. and Lane, B. (to Imperial Chemical Industries) (1976). US
Patent No. 3,933,689.
17. Anon. CEEPREE. Available at: http://www.chance-hunt.com/ceepree/
product.htm (accessed date December 28, 2010).
286 E. D. WEIL
18. Lin, S.-C. and Kent, B. (2009). Flammability of Fluoropolymers, In: Wilkie,
C., Morgan, A. and Nelson, G. (eds), Fire and Polymers V: Materials and
Concepts for Fire Retardancy, ACS Symposium Series 1013, pp. 294–295,
American Chemical Society, Washington, DC.
19. Duquesne, S., Jimenez, M. and Bourbigot, S. (2009). Fire Retardancy and
Fire Protection of Materials Using Intumescent Coatings – A Versatile
Solution? In: Hull, R. and Kandola, B. (eds), Fire Retardancy of Polymers:
New Strategies and Mechanisms (FRPM ‘07), 11th, Bolton, UK, 4–6 July,
2007 (published in 2009 by Royal Society of Chemistry, Cambridge, UK),
pp. 240–252.
20. Cagliostro, D.E., Riccitiello, S.R., Clark, K.J. and Shimizu, A.B. (1975).
Intumescent Coating Modeling, Journal of Fire and Flammability,
6: 205–221.
21. Anderson, Jr, C.E., Dziuk Jr, J., Mallow, W.A. and Buckmaster, J.
(1985). Intumescent Reaction Mechanisms, Journal of Fire Sciences,
3: 161–194.
22. Buckmaster, J., Anderson, C. and Nachman, A. (1986). A Model
for Intumescent Paints, International Journal of Engineering Science,
24: 263–276.
23. Shih, Y.C., Cheung, F.B. and Koo, J.H. (1998). Theoretical Modeling
of Intumescent Fire-Retardant Materials, JournalofFireSciences, 16:46–71.
24. Mamleev, V.Sh., Bekturov, E.A. and Gibov, K.M. (1998). Dynamics of
Intumescence of Fire-Retardant Polymeric Materials, Journal of Applied
Polymer Science, 70: 1523–1542.
25. Reshetnikov, I.S., Yablokova, M.Yu. and Khalturinskij, N.A. (1998).
Physical Aspects of Intumescence, Recent Advances in Flame Retardancy
of Polymeric Materials, Business Communications Co. Norwalk, CT, 1998,
Vol. 9, pp. 300–302.
26. Antonov, A.V., Reshetnikov, I.S. and Khalturinskij, N.A. (1999).
Combustion of Char-Forming Polymeric Systems, Russian Chemical
Reviews, 68: 605–614 (in English).
27. Reshetnikov, I.S., Yablokova, M.Yu. and Khalturinskij, N.A. (1997).
Influence of Surface Structure on Thermoprotection Properties of
Intumescent Systems, Applied Surface Science, 115: 199–201.
28. Koo, J. (1997). Thermal Characteristics Comparison of Two Fire Resistant
Materials, Journal of Fire Sciences, 15(3): 203–221.
29. Bhargava, A. and Griffin, G. (1999). A Two-Dimensional Model of Heat
Transfer Across a Fire Retardant Epoxy Coating Subjected to an Impinging
Flame, Journal of Fire Sciences, 17(3): 188–208.
30. Bhargava, A. and Griffin, G. (2003). Kinetics of Degradation Reactions
Within Intumescent and Subliming Fire Retardant Coatings, Journal of
Fire Sciences, 21(3): 173–188.
31. Griffin, G., Bicknell, A. and Brown, T. (2005). Study of the Effect
of Atmospheric Oxygen Content on the Thermal Resistance of Intumescent
Fire-Retardant Coatings, Journal of Fire Sciences, 23(4): 303–328.
32. Lautenberger, C. and Fernandez-Pello, C. (2009). Generalized
Pyrolysis Model for Combustible Solids, Fire Safety Journal, 44(6): 819–839.
Fire-Protective and Flame-Retardant Coatings 287
33. Bourbigot, S., Duquesne, S. and Leroy, J.-M. (1999). Modeling of Heat
Transfer of a Polypropylene-Based Intumescent System During
Combustion, Journal of Fire Science, 17(1): 42–56.
34. Bourbigot, S., Jimenez, M. and Duquesne, S. (2006). Modeling Heat Barrier
Efficiency of Flame Retarded Materials, In: Petit, J.M. and Squalli, O. (eds),
Comsol Multiphysics Conference 2006, Comsol France, Paris, 2006, pp. 59–65.
35. Jimenez, M., Duquesne, S. and Bourbigot, S. (2006). Intumescent Fire
Protective Coating: Toward a Better Understanding of Their Mechanism of
Action, Thermochimica Acta, 449: 16–26.
36. Gillet, M., Autrique, L. and Perez, L. (2007). Mathematical Model for
Intumescent Coating Growth: Application to Fire Retardant Systems,
Journal of Physics D: Applied Physics, 40: 883–899.
37. Dai, X.H., Wang, Y.C. and Bailey, C.G. (2009). Effects of Partial Fire
Protection on Temperature Development in Steel Joints Protected by
Intumescent Coating, Fire Safety Journal , 44: 376–386.
38. Branca, C., Di Blasi, C. and Horacek, H. (2002). Analysis of the Combustion
Kinetics and Thermal Behavior of an Intumescent System, Industrial and
Engineering Chemistry Research, 41(9): 2107–2114.
39. Reshetnikov, I.S., Antonov, A., Rudakova, T., Aleksjuk, G. and
Khalturinskij, N.A. (1996). Some Aspects of Intumescent Fire Retardant
Systems, Polymer Degradation and Stability, 54: 137–141.
40. Horacek, H. (2009). Reactions of Stoichiometric Intumescent Paints,
Journal of Applied Polymer Science, 113: 1745–1756.
41. Reshetnikov, I., Garashchenko, A. and Strakhov, V. (2000). Experimental
Investigation into Mechanical Destruction of Intumescent Chars, Polymers
for Advanced Technologies, 11(8–12): 392–397.
42. Reshetnikov, I.S., Yablokova, M.Yu., Potapova, E., Khalturinskij, N.A.,
Chernyh, V.Y. and Mashlyakovskii, L.N. (1998). Mechanical Stability
of Intumescent Chars, Journal of Applied Polymer Science, 67: 1827–1830.
43. Berlin, A.A., Khalturinskij, N.A., Reshetnikov, I.S. and Yablokova, M.Yu.
(1998). Some Aspects of Mechanical Stability of Intumescent Chars,
In: Le Bras, M., Camino, G., Bourbigot, S. and Delobel, R. (eds), Fire
Retardancy of Polymers: The Use of Intumescence, pp. 104–112, Royal
Society of Chemistry, Cambridge, UK.
44. Reshetnikov, I.S., Yablokova, M.Yu. and Khalturinskij, N.A. (1998). Special
Features of Bubble Formation During Intumescent Systems Burning,
In: Le Bras, M., Camino, G., Bourbigot, S. and Delobel, R. (eds), Fire
Retardancy of Polymers: The Use of Intumescence, pp. 140–151, Royal
Society of Chemistry, Cambridge, UK.
45. Reshetnikov, I.S. and Khalturinskij, N.A. (1998). The Role of Radiation over
Intumescent Systems Burning, In: Le Bras, M., Camino, G., Bourbigot, S.
and Delobel, R. (eds), Fire Retardancy of Polymers: The Use of Intumescence,
pp. 152–158, Royal Society of Chemistry, Cambridge, UK.
46. Jimenez, M., Duquesne, S. and Bourbigot, S. (2006). Multiscale
Experimental Approach for Developing High-Performance
Intumescent Coatings, Industrial and Engineering Chemistry Research,
45: 4500–4508.
288 E. D. WEIL
47. Jimenez, M., Duquesne, S. and Bourbigot, S. (2009). Kinetic Analysis of the
Thermal Degradation of an Epoxy-Based Intumescent Coating, Polymer
Degradation and Stability, 94(3): 404–409.
48. Bourbigot, S. and Le Bras, M. (1998). Synergy in Intumescence: Overview
of the Use of Zeolites, In: Le Bras, M., Camino, G., Bourbigot, S. and
Delobel, R. (eds), Fire Retardancy of Polymers: The Use of Intumescence,
pp. 222–234, Royal Society of Chemistry, Cambridge, UK.
49. Le Bras, M., Bourbigot, S., Siat, C. and Delobel, R. (1998). Comprehensive
Study of Protection of Polymers by Intumescence – Application to Ethylene
Vinyl Acetate Copolymer Formulations, In: Le Bras, M., Camino, G.,
Bourbigot, S. and Delobel, R. (eds), Fire Retardancy of Polymers: The Use
of Intumescence, pp. 266–278, Royal Society of Chemistry, Cambridge, UK.
50. Bertelli, G., Marchetti, E., Camino, G., Costa, L. and Locatelli, R. (1989).
Intumescent Fire Retardant Systems: Effect of Fillers on Char Structure,
Angewandte Makromolekulare Chemie, 172(2868): 153–163.
51. Scharf, D., Nalepa, R., Heflin, R. and Wusu, T. (1992). Studies on Flame
Retardant Intumescent Char, Fire Safety Journal, 19: 103–117.
52. Kozlowski, R., Wesolek, D. and Wladyka-Przybylak (to Instytut Wlokien
Naturalnych) (2009). US Patent Application No. 2009/0215926.
53. Series of articles mainly in Polymer Degradation and Stability summarized
and referenced in Camino, G. and Luda, M.P. (1998). Mechanistic Study
on Intumescence, In: Le Bras, M., Camino, G., Bourbigot, S. and Delobel, R.
(eds), Fire Retardancy of Polymers: The Use of Intumescence, pp. 48–63,
Royal Society of Chemistry, Cambridge, UK.
54. Bourbigot, M., Le Bras., M., Duquesne, S. and Rochery, M. (2004). Recent
Advances for Intumescent Polymers, Macromolecular Science and
Engineering, 289(6): 499–511.
55. Camino, G., Costa, L. and Trossarelli, L. (1985). Study of the
Mechanism of Intumescence in Fire Retardant Polymers: Part V –
Mechanism of Formation of Gaseous Products in the Thermal
Degradation of Ammonium Polyphosphate, Polymer Degradation and
Stability, 12: 203–211.
56. Marchand, R., Boukbir, L., Falchier, P., Laurent, Y., Bonnaud, O. and Roult,
G. (1988). L’Oxynitrure de Phosphore Massif PON, Le Vide, les Couches
Minces, 241: 231–232.
57. Boukbir, L., Marchand, R., Laurent, Y., Bacher, P. and Roult, G. (1989).
Preparation and Time-of-flight Neutron Diffraction Study of the
Cristobalite-type PON Phosphorus Oxynitride, Annales de Chimie, 14(8):
475–481.
58. Marchand, R., Laurent, Y. and Favennec, P. (to Centre Nationale de la
Recherche Scientifique et Etat Francaise repr. par Ministre des PTT).
French Patent Application No. 2,617,152 (30 December, 1988).
59. Taylor, A.P. and Sale, F.R. (1992). Thermal Analysis of Intumescent
Coatings, Polymers Paint Colours Journal, 182(4301): 1222–1225.
60. Taylor, A.P. and Sale, F.R. (1993). Thermoanalytical Studies of
Intumescent Systems, Macromolecular Chemistry, Macromolecular
Symposia, 74: 85–93.
Fire-Protective and Flame-Retardant Coatings 289
61. Futterer, T. (2006). Ammonium Polyphosphates, Special Chemicals
Magazine, July–August 2006: 34–36.
62. Watanabe, M., Sakurai, M. and Maeda, M. (2009). Preparation of
Ammonium Polyphosphate and Its Application to Flame Retardant,
Phosphorus Research Bulletin, 23: 35–44.
63. Dany, F.-J., Wortmann, J. and Kandler, J. (to Hoechst) (1977). US Patent
No. 4,009,137.
64. Pirig, W.-D. and Thewes, V. (to Clariant) (2001). US Patent No. 6,251,961.
65. Pirig, W.-D., Rothkamp, S. and Thewes, V. (to Clariant) (2000). US Patent
No. 6,054,513.
66. Ward, D. (to Intumescent Systems Ltd) (2009). European Patent
Application No. 2,093,263.
67. Weil, E. and Choudhary, V. (1995). Flame Retarding Plastics and
Elastomers with Melamine, Journal of Fire Science, 13(2): 104–126.
68. Mackay, J.S. (to American Cyanamid Co.) (1951). US Patent No. 2,566,231.
69. Ducrocq, P., Duquesne, S., Magnet, S., Bourbigot, S. and Delobel, R. (2006).
Interactions Between Chlorinated Paraffins and Melamine in Intumescent
Paint – Inventing a Way to Suppress Chlorinated Paraffins from the
Formulations, Progress in Organic Coating, 57(4): 430–438.
70. Kay, M., Price, A. and Lavery, I. (1979). A Review of Intumescent Materials,
With Emphasis on Melamine Formulations, Journal of Fire Retardant
Chemistry, 6 : 69–90.
71. Weil, E. and McSwigan, B. (1994). Melamine Phosphates and
Pyrophosphates in Flame Retardant Coatings: Old Products with New
Potential, Journal of Coatings Technology, 66(839): 75–82.
72. Thewes, V. and Pirig, W.-D. (to Clariant GmbH) (2001). US Patent
Application No. 2001/0027226.
73. Levchik, S., Levchik, G., Balabanovich, A., Weil, E. and Klatt, M. (1999).
Phosphorus Oxynitride. A Thermally Stable Fire-Retardant Additive for
Polyamide 6 and Polybutylene Terephthalate, Angewandte
Makromolekulare Chemie, 264: 48–55.
74. Hill, Jr J., (to Material Technologies & Sciences) (1993). US Patent No.
5,225,464.
75. Caltop SA (assignee) (1980). British Patent No. 1,575,708.
76. Aslin, C. (to Chemische Fabrik Budenheim; Rudolf A. Oetker) (1995). US
Patent No. 5,387,655.
77. Aslin, D. (to Prometheus Developments Ltd) (2004). British Patent
Application No. 2 401 367.
78. Gobelbecker, S., Nagerl, H.-D., Danker, G. and Kirk, D. (to Akro-Fireguard
Products; Chemische Fabrik Budenheim). European Patent Application
No. 0 614 944.
79. Bradford, S., Hallam, S. and Taylor, A. (to Leigh’s Paints) (2007). British
Patent Application No. 2,451,233.
80. Andersson, A., Lundmark, S. and Maurer, F. (2007). Evaluation and
Characterization of Ammonium Polyphosphate-Pentaerythritol-Based Systems
for Intumescent Coatings, Journal of Applied Polymer Science, 104(2): 748–753.
290 E. D. WEIL
81. Harden, A. and Velin, P. (to Perstorp Specialty Chemicals) (2006). PCT
Patent Application No. WO 2006096112.
82. Jenewein, E. and Pirig, W.-D. (to Hoechst AG) (1996). European Patent
Application No. 0 735 119.
83. Wang, J., Yang, S., Li, G. and Jiang, J. (2003). Synthesis of a New-Type
Carbonific and Its Application in Intumescent Flame-retardant (IFR)/
Polyurethane Coatings, Journal of Fire Sciences, 21(4): 245–266.
84. Wladyka-Przybylak, M. and Kozlowski, R. (1999). The Thermal
Characteristics of Different Intumescent Coatings, Fire and Materials,
23(1): 33–43.
85. Duquesne, S. and Bourbigot, S. (2009). Char Formation and
Characterization, In: Wilkie, C. and Morgan, A. (eds), Fire Retardancy of
Polymeric Materials, 2nd edn, pp. 239–260, CRC Press, Boca Raton, FL.
86. Horacek, H. (2009). Reactions of Stoichiometric Intumescent Paints,
Journal of Applied Polymer Science, 113(3): 1745–1756.
87. Ellard, J. (1973). Performance of Intumescent Fire Barriers, Division of
Organic Coatings and Plastics Chemistry, ACS 165th Meeting, Dallas, TX,
April 8–13.
88. Langille, K.B., Nguyen, D., Veinot, D.E. and Bernt, J.O. (to Pyrophoric
Systems Ltd) (2003). US Patent No. 6,645,278.
89. Langille, K.B., Nguyen, D., Bernt, J.O., Veinot, D.E. and Murthy, M.K.
(1993). Constitution and Properties of Phosphosilicate Coatings, Journal of
Materials Science, 28(15): 4175–4187.
90. Veinot, D., Nguyen, D., Langille, K. and Sorathia, U. (1999). Inorganic
Intumescent Coating for Improved Fire Protection of GRP,
44th International SAMPE Symposium, Long Beach, CA, 23–27 May,
pp. 1385–1394.
91. Wainwright, R. and Evans, K. (to Alcan International Ltd) (1996). US
Patent No. 5,532,292.
92. Erismann, D. and Vesley, G. (to 3M) (2002). US Patent Application No.
20020171068.
93. Phillips, G. (to National Research Development Corp.) (1974). British
Patent No. 1,373,908.
94. Dimanshteyn, F. (to Firestop Chemical Corp.) (1991). US Patent No.
5,035,951.
95. Hanafin, J. (to Textron) (2000). US Patent No. 6,096,812.
96. Jimenez, M., Duquesne, S. and Bourbigot, S. (2006). Characterization of the
Performance of an Intumescent Fire Protective Coating, Surface and
Coatings Technology, 201: 979–987.
97. Jimenez, M., Duquesne, S. and Bourbigot, S. (2006). Intumescent Fire
Protective Coatings: Toward a Better Understanding of Their Mechanism of
Action, Thermochimica Acta, 449: 16–26.
98. Nugent, R., Ward, T., Greigger, P. and Seiner, J. (to PPG Industries). US
Patent No. 5,108,832.
99. Ward, T., Greigger, P., Matheson, R., Alveberg, B.-E. and Alveberg, J.
(1996). Epoxy Intumescent Coatings, PCE, Dec 1996: 16–23.
Fire-Protective and Flame-Retardant Coatings 291
100. Kobayashi, N., Yoshioki, S., Yoshida, K., Sagawa, K. and Ishihara, S.
(to Dainippon Ink and Chemicals, Inc.) (1995). US Patent No. 5,401,793.
101. Gottfried, S. (to No Fire Technologies, Inc.) (1998). US Patent No.
5,723,515.
102. Green, J., Allen, W., Taylor, A. and Butterfield, S. (to W. & J. Leigh & Co.)
(2006). PCT Patent Application No. WO 2006/067478.
103. Olcese, T. and Pagella, C. (1999). Vitreous Fillers in Intumescent Coatings,
Progress in Organic Coatings, 36: 231–241.
104. Koo, J., Ng, P. and Cheung, F. (1997). Effect of High Temperature
Additives in Fire Resistant Materials, Journal of Fire Sciences, 15(6):
488–504.
105. Koo, J.H. and Pilato, L.A. (2006). Fire-Retardant Nanocomposite Coatings,
part of chapter 16, Thermal Properties and Microstructures of Polymer
Nanostructured Materials, In: Schulz, M.J., Kelkar, A. and Sundaresan,
M.J. (eds), Nanoengineering of Structural, Functional and Smart
Materials, pp. 414–416, CRC Press, Boca Raton, FL.
106. Hassan, M., Kozlowski, R. and Obidzinski, B. (2008). New Fire-Protective
Intumescent Coatings for Wood, Journal of Applied Polymer Science,
110(1): 83–90.
107. Camino, G. and Fina, A. (2008). New Perspectives in Fire Retardant
Coatings, Pitture e Vernici: European Coatings, 7(64): 1–5.
108. Malucclli, G., Han, Z., Fina, A. and Camino, G. (2010). Intumescent
Coatings for the Protection of Steel Structures: State of the Art and
Perspectives, paper presented at Fire Retardant Coatings IV, European
Coatings Conference, Berlin, Germany, 3–4 June.
109. Hu, X. and Koo, J.H. (2001). Flammability Studies on a Water-Borne
Flame Retardant Nanocomposite Coating on Wood, paper presented at
Proceedings of Polymer Nanocomposites Symposium, ACS Southwest
Regional Meeting, San Antonio, TX, 17–20 October.
110. Wang, Z., Han, E. and Ke, W. (2006). Effect of Acrylic Polymer and
Nanocomposite with Nano-SiO
2
on Thermal Degradation and Fire
Resistance of APP-DPER-MEL Coating, Polymer Degradation and
Stability, 91(9): 1937–1947.
111. Rhodes, M., Izraelev, L., Tuerack, J. and Rhodes, P. (to Broadview
Technology) (2004). PCT Patent Application No. WO 2004/009691.
112. Liu, F. and Zhu, W. (to J.M. Huber Corp.) (1999). US Patent No. 5,968,669.
113. Hallisey, G., Higbie, W., Camarota, A. and Rowan, J. (to Avtec Industries)
(2005). US Patent No. 6,960,388.
114. Rowen, J. (to Avtec Industries) (2008). US Patent No. 7,331,400.
115. Ford, B., Hutchings, D., Foucht, M., Qureshi, S., Garvey, C. and
Krassowski, D. (to Georgia-Pacific Resins) (2001). US Patent No.
6,228,914.
116. Benitez, J. and Giudice, C. (1998). Phosphorus-Based
Intumescent Coatings, Cidepint, 1997–1998: 45–62; Chemical Abstract,
130: 169582.
292 E. D. WEIL
117. O’Brien, P. and Schofield, C. (to Fire & Vision Ltd) (2000). PCT Patent
Application No. 00/14167.
118. Duquesne, S., Delobel, R., Magnet, S. and Jama, C. (to Eliokem) (2004).
European Patent Application No. 1 431 353.
119. Fream, A. and Magnet, S. (2004). The Development of Novel Latexes
for Fire-Resistant Intumescent Coatings, Paint and Coatings Industry,
June 2004: 64–73.
120. Magnet, S., Duquesne, S., Delobel, R. and Jama, C. (to Eliokem S.A.S.)
(2003). US Patent No. 7,105,605.
121. Duquesne, S., Magnet, S., Jama, C. and Delobel, R. (2004). Intumescent
Paints: Fire Protective Coatings for Metallic Substrates, Surface and
Coating Technology, 180–181: 302–307.
122. Duquesne, S., Magnet, S., Jama, C. and Delobel, R. (2005). Thermoplastic
Resins for Thin Film Intumescent Coatings – Towards a Better
Understanding of their Effect on Intumescence Efficiency, Polymer
Degradation and Stability, 88(1): 63–69.
123. Green, J. and Allen, W. (to W. & J. Leigh) (2005). PCT Patent Application
No. WO 2005/000975.
124. Green, J., Allen, W. and Taylor, A. (to W. & J. Leigh & Co.) (2006). PCT
Patent Application No. WO 2006/067488.
125. Farrell, P. and Green, J. (to W. & J. Leigh & Co.) (2002). PCT Patent
Application No. WO 02/096996.
126. Schmitt, G., Neugebauer, P., Scholl, S., Heeb, H., Reinhard, P. and
Ku¨hl, G. (to Evonik Ro
¨hm
GmbH). PCT Patent Application No. WO 2009/
013089 (2009).
127. Ward, T., Greer, S., Boberski, W. and Seiner, J. (1985). US Patent No. 4
529 467.
128. Ward, T., Greigger, P. and Seiner, J. (1991). US Patent No. 5 070 119.
129. Nugent, R., Ward, T., Greigger, P. and Seiner, J. (1992). US Patent No. 5
108 832.
130. Sinclair, M. and Watts, J. (2008). US Patent No. 7 217 753.
131. Hanafin, J. and Bertrand, D. (2000). US Patent No. 6 096 812.
132. Thewes, V. and Hennemann, A. (2008). European Patent No. 1 627 896.
133. Gottfried, S. (to No Fire Technologies Inc.) (2000). US Patent No.
6,074,714.
134. Gottfried, S. (to No Fire Technologies Inc.) (1999). US Patent No.
5,985,385.
135. McGinniss, V., Dick, R., Russell, R. and Rogers, S. (to Battelle Memorial
Institute) (1999). US Patent No. 5,925,457.
136. De Keyser, F. (to Monsanto Europe SA) (1995). US Patent No. 5,413,828.
137. Reyes, J. (to JJI Technologies LLC) (2008). US Patent Application No.
2008/0277136.
138. Nuzzo, C. (to United States Mineral Products Co.; Isolatek International)
(2007). PCT Patent Application No. WO 2007 102,080.
Fire-Protective and Flame-Retardant Coatings 293
139. Anon. (2009). New Intumescent Protects SPF from Fire, Durability þ
Design (the Journal of Architectural Coatings). Available at: http://
durabilityanddesign.com/news/?fuseaction¼view&id¼3347 (accessed date
November 17, 2009).
140. Hansel, J.-G. and Mauerer, O. (to Lanxess Deutschland GmbH) (2009). US
Patent Application No. 2009/0220762.
141. Mabey, M. and Kish, W. (to No-Burn Investments LLC) (2009). US Patent
No. 7,482,395.
142. Mabey, M. and Kish, W. (to No-Burn Investments LLC) (2008). US Patent
Application No. 2008/00542390.
143. Caze, C., Devaux, E., Testard, G. and Reix, T. (1998). New Intumescent
Systems: An Answer to the Flame Retardant Challenges in the Textile
Industry, In: Le Bras, M., Camino, G., Bourbigot, S. and Delobel, R. (eds),
Fire Retardancy of Polymers: The Use of Intumescence, pp. 363–375,
Royal Society of Chemistry, Cambridge, UK.
144. Marcu, I., Shah, P., Cornman, S., Horvath, S., Church, J. and Reeves, D.
(to Noveon) (2008). US Patent Application No. 2008/0124560.
145. Fukuzumi, T., Shirazawa, K. and Uchida, K. (to Nissin Chemical Industry
Co.) (2009). US Patent Application No. 2009/0215932.
146. Horrocks, A.R., Wang, M.Y., Hall, M.E., Sunmonu, F. and Pearson, J.S.
(2000). Flame Retardant Textile Back-Coatings. Part 2. Effectiveness of
Phosphorus-Containing Flame Retardants in Textile Back-Coating
Formulations, Polymer International, 49: 1079–1091.
147. Bonduel, T. (2010). Carbon Nanotubes/Silicone Nanocomposites for Flame
Resistant Coatings, paper presented at Fire Retardant Coatings IV,
European Coatings Conference, Berlin, Germany, 3–4 June.
148. Pandee, J.L and Banerjee, M.K. (1997). High-Temperature-Resistant
(Slurry-Based) Coatings, Anti-Corrosion Methods and Materials, 44(6):
368–375.
149. Burton, D. and Holm, J. (to High Performance Coatings Inc.) (2008). PCT
Patent Application No. WO 2008060699.
150. Alexander, G., Cheng, Y.-B., Burford, R., Shanks, R., Mansouri, J., Hodzic,
A., Wood, C., Genovese, A., Barber, K. and Rodrigo, P. (to Polymers
Australia PTY Ltd) (2004). PCT Patent Application No. WO 2004/013255.
151. Alexander, G., Cheng, Y.-B., Burford, R., Shanks, R., Mansouri, J., Barber,
K., Rodrigo, P. and Preston, C. (to Ceram Polymerik Pty Ltd) (2007). US
Patent Application No. 2007/0246240.
152. Thompson, K., Rodrigo, P., Preston, C. and Griffin, G. (2006). In the Firing
Line, European Coatings Journal, 12: 34–39.
153. Al-Hassany, Z., Genovese, A. and Shanks, R. (2010). Fire-Retardant and
Fire-Barrier Poly(vinyl acetate) Composites for Sealant Applications,
Express Polymer Letters, 4(2): 79–93.
154. Sorathia, U., Gracik, T., Ness, J., Hunstad, M. and Berry, F. (2003).
Evaluation of Intumescent Coatings for Shipboard Fire Protection,
Journal of Fire Sciences, 21(6): 423–450.
155. Hanafin, J. and Hu, Y. (2002). Intumescent Coatings for the Protection
of Steel, paper presented in Recent Advances in Flame Retardancy
294 E. D. WEIL
of Polymeric Materials, 13th Annual BCC Conference, Stamford, CT,
3–5 June.
156. Koo, J.H., Wootan, W., Chow, W.K., Au Yeung, H.W. and Venumbaka, S.
(2001). Flammability Studies of Fire Retardant Coatings on Wood,
Chapter 28, In: Nelson, G.L. and Wilkie, C.A. (eds), Fire and
Polymers Materials and Solutions for Hazard Prevention, ACS
Symposium Series 797, American Chemical Society, Washington, DC, pp.
361–374.
157. Gottfried, S. (2002). Fire Protection Coatings and the SOLAS codes, paper
presented in Recent Advances in Flame Retardancy of Polymeric Materials,
13th Annual BCC Conference, Stamford, CT, 3–5 June.
158. Jimenez, M., Duquesne, S. and Bourbigot, S. (2006). High-Throughput Fire
Testing for Intumescent Coatings, Industrial and Engineering Chemistry
Research, 45(22): 7475–7481.
159. Bishop, D., Bottomley, D. and Zobel, F. (1983). Fire Retardant Paints,
Journal of the Oil and Colour Chemists Association, 66(12): 373–395.
160. Landin, H. (to Minnesota Mining and Manufacturing) (1998). US Patent
No. 5,830,319.
161. Buckingham, M. and Welna, W. (to 3M) (2004). US Patent No. 6,747,074.
162. Welna, W. (to Minnesota Mining and Manufacturing) (1996). US Patent
No. 5,578,671.
163. Reinheimer, A., Wenzel, A. and Muenzenberger, H. (to Hilti AG) (2009).
US Patent No. 7,479,513.
164. Muenzenberger, H., Heimpel, F., Rump, S., Forg, C. and Lieberth, W.
(to Hilti AG) (2004). US Patent No. 6,706,774.
165. Ackerman, E. (to Rectorseal Corp.) (2001). US Patent No. 6,207,085.
166. Stahl, J. (to Specified Technologies Inc.) (1992). US Patent No. 5,137,658.
167. Schauber, T., Hellback, B., Baser, E. and Malrose, N. (to Doyma GmbH)
(2009). European Patent Application No. 2 088 183.
168. Zweynert, M. (2009). Flame Retardant Gelcoats, paper at presented at
Thermosets 2009 From Monomer to Components, Berlin, Germany,
September 30, 2009.
169. Norwood, L. (1999). Fire resistance to satisfy market needs, paper in
Composites in Fire, Proceedings of the International Conference, 1st,
Newcastle upon Tyne, UK, 15–16 September (published in 2001 by
Woodhead Publishing Ltd, Cambridge, UK). pp. 24–37.
170. Reilly, T. and Dietz, M. (2009). Flame Retarded Thermoset
Materials Based on Phosphorus Chemistry, paper presented at
Thermoset Resin Formulators Association meeting, Pittsburgh, PA,
14–15 September.
171. Pagella, C., Epifani, R. and Baldi, G. (2008). New Driving Forces
for Intumescent Coatings, Pitture e Vernici, European Coatings, 84(4):
17–29.
172. Mabey, M. and Kish, W. (2010). US Patent Application No.
20100069488.
173. Kawamura, Y. (to Kikusui Chemical Industries, Ltd) (2010). Japenese
Kokai Tokkyu Koho 138,217; Chemical Abstracts, 153: 64492.
Fire-Protective and Flame-Retardant Coatings 295
BIOGRAPHY
Edward D. Weil
Dr. Weil received his BS degree in chemistry from University of
Pennsylvania in 1950 and his PhD degree in organic (polymer)
chemistry from University of Illinois in 1953. He conducted and
managed research in industry (Hooker Chemical Co., Stauffer
Chemical Co.) for 33 years and has served as Research Professor at
Polytechnic University (now Polytechnic Institute of NYU) since 1987.
His industrial and academic research has covered a wide variety of flame
retardancy topics, has led to many patents and several commercial flame
retardants and he consults actively in this field. He has authored many
papers and encyclopedia articles in flame retardants, phosphorus,
chlorine and sulfur chemistry. The present review supplements his
co-authored book (2009) on flame retardants for plastics and textiles.
296 E. D. WEIL
