Rumynskaya E.I., Kuzmenkov M.I. Production of Phosphate Binder Fire-protective Coating for Steel

7/23/2019 Rumynskaya E.I., Kuzmenkov M.I. Production of Phosphate Binder Fire-protective Coating for Steel...

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ISSN 1683-0377. Proceedings of BSTU. 2012. Issue 3. Chemistry and Technology of Inorganic Substances 54

UDC 666.949:666.767

E. I. Rumynskaya, junior researcher

(SE Institute of Dwelling NIPTIS named after S. S. Atayev);

M. I. Kuzmenkov, D. Sc. (Engineering), professor (BSTU)

PRODUCTION OF PHOSPHATE BINDER FIRE-PROTECTIVE COATINGFOR STEEL BUILDING CONSTRUCTIONS

Brief analysis of means for fire protection of steel building constructions was given, special atten-tion being paid to the advantages of using phosphate binders for protective coatings. The compositionof fire-protective coating based on cold-cured phosphate binder was developed, its properties being tho-roughly examined.

Introduction. The problem is vital as there is asteady growth of social and economic damagesfrom fire in the Republic of Belarus. Data show [1]the tripled quantity of fires, four-times increase inmortality and the damage of 1% GDP during the

past 25 years.According to the Emergencies Ministry sta-

tistics in 2011 there were about 9 thousand firesin the Republic of Belarus that took more than1.2 thousand lives and destroyed 1.5 thousand

buildings.One of the least protected structural parts is

steel supporting structures. For most steels thecritical temperature is considered to be 500

oC,

higher temperatures causing deformation and al-most immediate destruction of such structures [2].

To protect steel constructions against fire mate-rials of the 1

stflameproof degree are needed, which

are capable to ensure their heat insulation underfire attack at temperatures of up to 1,100

oC within

150 min [3, 4].The main components of fire-protecting means

determining their properties are binders. Thesecreate the coating, determine its main physical,chemical and performance characteristics, i.e. en-sure its fire resistance, adhesion to substrate, dura-

bility, etc.To make 1

st degree fire-protective coatings

special fillers and modifying additives are usedthat are stable to the action of heat flow and pre-

serve their properties under fire attack.Fire protective compound [57] includes the

following ingredients: refractory materials capable to preserve their

properties at high temperatures; swelling or swollen materials capable to pro-

vide heat insulation of the construction; materials including chemically bound water; antipyrines: fusible borates, phosphates and

silicates and/or materials decomposing whenheated and emitting gases which do not supportcombustion.

During decomposition of fire-retardants apart of heat is used to suppress endothermicprocess, thereby raising ignition temperature.

Noncombustible gas evolved prevents flamefrom spreading.

Nowadays various types of fire-protecting ma-terials possessing different flame resistance degreeare produced and applied in the CIS. They are pre-

pared on the basis of organic and inorganic bind-ers, fillers and modifying additives.

Swelling coatings based on organic binders[8, 9] are easy to produce and have good architec-tural, decorative and industrial characteristics.However, they can increase the fire-resistancelimit of constructions only within 1 h, and com-

bustion products of such materials are toxic andmay lead to mass asphyxia in case of fire. Thecoatings concerned are insufficiently stable under

production air conditions and high humidity, thatin case of a long-time service (more than 3 years)leads to emerging and developing corrosion cen-

ters on the steel construction and under the coat-ing, to adhesive strength deterioration, coatingdelamination and cracking resulting in reducedflame resistance time.

Such coatings may be of the following domes-tic and foreign trademarks: Agnitherm M (Belarus),Agnitherm MP (Belarus), Sinatherm 1 (Belarus),GARD (Belarus), Protherm CE (Russia), PhoenixCTC (Russia), Phoenix CTB (Russia), UnithermADR (Germany), Tikra Termostop (Slovenia).

Fire-protective mixtures based on liquid glassare suitable for indoor application at relative hu-

midity of not more than 60%, and, therefore, can-not be used out-of-doors. However, for many con-structions outside protection is much more vital.Moreover, such materials cannot be stored for along time, they are less productive in comparisonwith dry compounds, fragile, possess low adhesionand insufficient climatic stability and durability.With time passing the materials are covered withspots (whitish layer) and cracks, that deterioratesdecorative and service properties of finished sur-faces. The reason is carbonizing chemical inter-action of the compounds concerned with carbon

dioxide and other reactive gases from the air.Phosphate-binder-based fire-protective means

are used for the protection of steel [10]. Such


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Chemistry and Technology of Inorganic Materials and Substances 55

materials [11] preserve their properties at tem-peratures up to 1,600

oC, have flameproof limit

of at least 150 min, they are water-resistant, i.e.suitable for both indoor and outdoor applica-tions. Phosphate-binder-based compounds are

widely used in the USA, China, Japan and manyother countries, that is confirmed by numerouspatents and publications [1215]. Besides, phos-phate compounds are applied industrially as fire-retardants in many fire-protective materials con-taining organic binders.

All the above mentioned allows to concludethat in the Republic of Belarus there is an acuteneed to protect metal constructions from fire, butthere are no materials of domestic production withflameproof limit of 150 min.

The aim of the present research is to preparecheap and effective materials of the 1

stflameproof

degree for protecting steel constructions and tostudy their properties.

Main part.Having examined the main typesof binders and fire-protection means it can beconcluded that the basic requirements to fire-

protective compounds of the 1st flameproof de-

gree are: ability to preserve their properties under

temperatures of up to 1,100oC within at least

150 min; ability to insulate fire heat flow, to prevent

protected materials from destruction;

durability; water resistance; adhesion to steel constructions; ability to inhibit corrosion of steel con-

structions; no toxic materials evolved under fire

impact.And it is phosphate-binder-based fire-protec-

tive compositions that mostly comply with theserequirements. Such types of binders provide thehighest fire-resistance limits as they are mainlyrefractory materials that are stable to heat flow

and preserve their structure and properties underheat impact.

Monomeric phosphates are the most suitableones for fire-protective compounds. The reason isthat the original monomeric anion being a con-stituent part of the acid salt (orthophosphate) iscapable to polycondensate, with temperature in-creasing. It leads to the formation of chemically

bound water at 150170oC and, consequently, ofthe dimer (pyrophosphate). The dehydration proc-ess is endothermic and decreases the temperatureof the fire. Water vapor formed blocks the way of

heat flow to the construction, and of oxygen to firesite. Chemically bound water formation stops onlyat 450

oC when metaphosphates (polyphosphates)

are formed. Besides, another advantage of mono-meric anion is the fact that monomer in the acidsalt will show adhesive properties, the adhesion

being determined by chemical interaction of acidsalt with surface iron-oxide film of the steel build-

ing constructions face.Metals (Na, Ca, Mg, Al) can be used as a ca-tion in phosphate binders, as it is metal cations thatwhen interacting with phosphates reveal somewhatsimilar characteristics. Ammonium salt may also

be used for this purpose. It is preferable, however,to use ammonium phosphates, as at high tempera-tures the ammonium cation may self-decomposeevolving nonflammable gaseous products (ammo-nia) and, therefore, contribute to blocking combus-tion zones. Moreover, at further temperature im-

pact ammonia decomposes into nitrogen and hy-drogen with energy losses, which decreases thetemperature of the fire.

Summarizing the above mentioned and takinginto account the economic factor it may be con-cluded that the raw material component can beammophos consisting mainly of ammonium dehy-drophosphate with a small portion of ammoniumhydrophospate.

However, ammophos is not widely used forfire protection of steel constructions as ammonium

phosphates are not stable on exposure to theweather, not waterproof and require heat treatmentfor hardening.

To make fire-protective materials capable toharden in cold-weather conditions a magnesium-containing compound was added to the basic com-

position. But for magnesium-phosphate binders thesetting time is 12 min even with retarder (510%of weight). Adding more retarder is technically andeconomically not expedient.

Considering all this the fire-protective mate-rial was developed on the basis of magnesium-chrome-phosphate binder, it possessing longersetting time and, moreover, better anticorrosion

properties when used for steel constructions.

When producing such binders a secondary refrac-tory material (periclase-chromite, chromite-peric-lase, etc.) can be used as a neutralizing agent for

phosphoric acid [16]. It should be noted that theNH4H2PO4 (NH4)2HPO4 MgO Cr2O3 H2Osystem has not been studied yet, and no data con-cerning the crystallization processes on whichhardening of the composition involved is basedhave been found in recent publications. The studyof the phase formation process in such a system innon-equilibrium conditions is of scientific inter-est. The results obtained will al-low to control the

binder formation process and will thereby con-tribute to the study of the chemistry and technol-ogy of phosphate materials.


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ISSN 1683-0377. Proceedings of BSTU. 2012. Issue 3. Chemistry and Technology of Inorganic Substances 56

Hence, the fire-protective material was devel-oped on the basis of used periclase-chromite re-fractory, ammophos and vermiculite.

For better adhesion of the coating to steel con-structions and more productive application

process polymeric additives were used redis-persible polymeric powder and cellulose ester.Boric acid was added to the compound in order tocontrol the performance time, i. e. that of settingand hardening.

The composition of the fire-protective coatingwas optimized by varying the quantity of the com-

ponents mentioned in the following range: binder 5060 wt %, binder hardener 4050 wt %, thecontent of vermiculite being 530 wt %, of boricacid 37 wt %, of polymeric additives 0.24.0 wt % that of the binder. The research resultsare presented in Fig. 14.

The investigation revealed that at temperaturesof 300 and 900oC adhesion and compression strengthwere lower because of structural and phase trans-formations in the composition.

According to some authors [17], MgNH4(PO4)3and MgO form at the temperature of approximately300oC, and at 900oC the formation of orthophos-

phate -Mg3(PO4)2 is X-rayed, this explaining theresults obtained.

The present research has revealed that with thedeveloped material layer thickness of 5 cm and its515 kg/m2use a steel construction fireproof limitis at least 150 min. Therefore the coating can berecommended for outside applications.

The results of further investigations on phos-phate binder fire-protective coatings for steelconstructions will be presented in future pub-lications.

0

0,2

0,4

0,6

0,8

1

1,2

10 20 30 40 50 60 70 80

, %

,

Fig. 1. The dependence of the compressive

strength of the fire-protective composition

of the content ammophos

Fig. 2. The influence of ammonium phosphate

flame retardant composition

for adhesion

0

0,2

0,4

0,6

0,8

1

1,2

,

20 200 400 600 800 1000

,

,

20%

0

5

10

15

20

25

0 200 400 600 800 1000 1200

,

,

20%

Fig. 3. The dependenceof the flame-retardant adhesivecomposition on the temperature

Fig. 4. Effect of temperatureon the compressive strength

of the flame-retardant composition

0

5

10

15

20

25

10 20 30 40 50 60 70 80

, %

,

30

25

20

15

10

5

0

ompressive

strength,

MPa

10 20 30 40 50 60 70 80

Ammonium phosphate content, %10 20 30 40 50 60 70 80

mmonium phosphate content, %

Adhesion,

MPa

1.2

1.0

0.8

0.6

0.4

0.2

0

Compressivestrength,

MPa

20 200 400 600 800 1,000

Temperature,

0 200 400 600 800 1,000 1,200

Temperature,

unadulterated unadulterated20% vermiculite 20% vermiculite

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

Adhesio

n,

MPa

0

5

10

15

20

25


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Chemistry and Technology of Inorganic Materials and Substances 57

Conclusion. The composition of fire-protec-tive coating including ground periclaso-chromiterefractory, ammophos, boric acid, redispersive

polymeric powder and cellulose ester has been de-veloped. Its performance parameters have beendetermined. Preliminary cost calculations of phos-

phate- binder -based coatings have shown that theyare 510 times cheaper in comparison with liquid-glass-based ones, and 30 times in comparisonwith swelling organic fire-protective compounds.Materials developed are effective and accessibleand can be widely applied in building complexes.

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Rumynskaya E.I., Kuzmenkov M.I. Production of Phosphate Binder Fire-protective Coating for Steel