DeVeloPMent of fIre resIstAnt CoAtInG for the ProteCtIon of eleCtrICAl

Наводяться результати оптимізації складу вогнестійкого покриття для захисту кабельної ізоляції під час пожежі в замкнутому просторі. Компоненти покриття вибрані за вимогами вогнестійкості та токсичності. Обґрунтовано передбачуваний механізм роботи вогнестійкого покриття під час пожежі. Проведено лабораторні випробування зразків вогнестійких покриттів. Отримано часову залежність температури на зворотному боці вогнестійкого покриття від складу композиції. Ключові слова: нетоксичне вогнестійке інтумесцентне покриття для захисту кабельної ізоляції, компоненти складу, методика випробувань. Korostylev l., Kochanov V., Geyko s., yuresko t.


Introduction
The development of fireresistant materials and coa tings in Ukraine is a strategic direction in the sphere of rational use and protection of material and fuelenergy resources.The relevance of the composition optimization of fireresistant intumescent coatings is due to the fact that they are relatively thinlayered, do not emit a significant amount of toxic substances when heated, and have a high flame retardant efficiency.And also can be applied to the protected surface by different mechanized methods.The thickness and volume of fireresistant coating increase tens of times at the action of high temperature due to the for mation of a nonflammable and solid foamed layer (coke) with a density of 3•10 -3 -3 •10 -2 g/cm 3 and a of thermal conductivity coefficient like thermal conductivity of air.
The fireresistant coatings are especially effective in fires in confined spaces of engineering structures -ship rooms, nuclear and thermal power stations, at petrochemi cal enterprises and other potentially dangerous objects.

the object of research and its technological audit
The object of research is the composition of the fire resistant swelling coating.
The main problem of electric cables fire protection in a confined space is a high concentration of toxic sub stances in the composition of combustion products, which makes it difficult fire extinguishing works.This is due to the fact that the cables polymer insulation (polyethylene, polyvinyl chloride) and traditional flame retardant coatings based on epoxy and phenolic resins contain potentially hazardous substances.These substances during combustion are form toxic compounds (chlorine, carbon monoxide, hydrogen cyanide).
Experimental research of different compositions the fireresistant intumescent coatings on the basis of a po tentially safe silicone resin was carried out to reveal the peculiarities operation of the coating during a fire.
On the initial stage of development of fireresistive coating composition, «Pentelast 712 А» (or its analogue) the silicone resin, was chosen as a binder.This resin has good technological characteristics (low viscosity and har dening under temperatures of 20-30 °С) not toxic and water resistant.Its disadvantages are: the low mechani cal (1.5-3 MPa) and adhesive strength (up to 0.3 MPa) which can be increased by primer (special base coat for better adhesion).For the fireresistive coating swelling under the sharp temperature rise, the following mineral and polymeric fine divided fillers are proposed to intro duce into the composition: -alkaline earth metal hydroxides Al(OH) 3 и Mg(OH) 2 are thin white powder, waterinsoluble, in most (un der 0.12-0.Therefore, initially all the basic components of intumes cent fireresistant coating meet the requirements for heat resistance, low water absorption and low toxicity.Besides, the small size of fillers allows to create a coating thickness Technology audiT and producTion reserves -№ 6/1(38), 2017 ISSN 2226-3780 300-500 μm, this will make a positive impact on techni cal and economic characteristics of fireresistant coating.
Mechanism of work of the fireresistant coating under the chosen composition will as follows: On the initial stages of temperature rise (up to 190-200 °С) the fireresistant coating will have no visually observed changes of material structure because of high heat resistance of silicone resin.Later, with the growth of temperature decomposition of Al(OH) 3 , starts with water escape and partial fireresistive coating foaming.
When temperature rises to 270 °С chemical processes involving decomposition of (NH 4 PO 3 ) n and C(CH 2 OH) 4 , start with intensive gas escape and foaming of upper layers of fireresistant coating.The coke layer starts to form.
Almost at once, under temperature of 290 °С the thermal decomposition of Mg(OH) 2 , magnesium hydroxide, starts with water escape, additional foaming of the fireresistant coating and heat release.
The newly formed MgO strengthens the coke layer.Under temperature of 350 °С melamine C 3 H 6 N 6 , the last active component, decomposes.It is a filmforming agent which finally consolidates the coke layer of the intumes cent fireresistant coating.
It should be noted that under open flame impact tem perature raises too fast, therefore all thermal and chemical process happen almost simultaneously, touching the thin outer layer of the fireresistive coating.Due to foaming the thickness of fireresistive coating increases in 20-30 times, forming the thick and incombustible coked cellular layer of low thermal conductivity; this layer secures the inner layers of the material.Therefore, usually there is no need in making the fireresistive coating thicker than 1-2 mm.
Under fire condition the function of the active compo nents of fireresistant coating is carried out finely dispersed fillers and the silicone resin is thermally decomposed to silicon oxide and is chemically neutral.
It is of interest in this connection to optimize the composition of fireresistant coating and maximize increase the filler content, but without compromising the techno logical characteristics of the composition.

the aim and objectives of research
The aim of research is optimization of the fireresistant coating composition for increase in its fireproof proper ties.At the same time the fireresistant coating has to be adapted for drawing on electric cables directly in situ of their installation in enclosed space.
To achieve this aim, it is necessary perform the fol lowing objectives: 1. To define influence of composition the fireresistant coating on the basis of silicon resin, namely the ratio of the components of the intumescent complex -ammonium polyphosphate, pentaerythritol and melamine, on the fire proof properties.
2. To reduce the toxicity of both the components of fireresistant coating and the products of its thermal de struction in case of fire.

research of existing solutions of the problem
The fireresistant coatings are multicomponent compo site materials.At influence of a flame in process of tem perature increasing the various physical and chemical processes are consistently flows in the intumescent fire resistive coating.Various physical and chemical processes are consistently flow in the intumescent fireresistive coa ting at influence of a flame in process of temperature increasing.A stable foamcoke layer with a low thermal conductivity is formed, as a result, which protects the structure from action of high temperatures a sometime.Intumescent technologies are the most effective means of fires protection [1].
In recent years the direction on creation of fireresistant coating was created, which do not contain halides because volatile products of their thermal decomposition are toxic and corrosionactive substances [2].
The fireresistant coatings based on mineral binders (ce ment, aluminosilicate) are relatively inexpensive, but have a large coefficient of temperature expansion and low water resistance, so they have high adhesion to various surfaces during operation [3].
Application of various polymers in the form of syn thetic resins and their aqueous dispersions as binders of fireresistant coatings allows them to significantly increase their water resistance and adhesion strength, to reduce the mass and thickness of the coatings.However, at the same time, the amount of toxic substances and smoke released during a fire increases, especially when epoxy resins are used in fireresistant coatings [4].Application of aqueous disper sions of polymers [5] reduces the water resistance of the fireresistant coatings composition.Especially unfavorable conditions for the exploitation of coatings are the tropical climate that narrows geography and the sphere of their application.
Swelling of coatings perhaps in the presence in their composition intumescent complex and consist of ammo nium polyphosphate, pentaerythritol and melamine.The degree of swelling depends on the relationship between these components, the type of binder and the presence of other functional fillers [6], and the thickness of the coating can be increased tens of times.
It is difficult to establish the mechanism of interaction between individual components of intumescent coatings, in view of the high rate of their heating during a fire.Va rious reactions can occur between the coating compo nents, especially at high temperatures.It is difficult to predict the direction of hightemperature reactions.
Interaction between components of intumescent com plex is usually reduced to their successive endothermic decomposition with the release of a large number of non combustible gases -carbon dioxide, ammonia and water vapor, which carry off a significant amount of heat, and the solid phase of the products of chemical reactions forms a foamcoke.
The foamcoke is a solid porous structure with a low coefficient of thermal conductivity, which is able to pro tect the surface from the effects of the flame for some time.Efficiency of such protection is largely determined by the initial thickness of the coating and the swelling coefficient [7].
The components of the standard intumescent complex begin to swell at temperatures above 250 °C, while the temperature of beginnings of inflaming of wood and the softening of most polymers is less than 200 °C.
Therefore, mineral fillers which contain bound water are introduced in composition; these are alkaline earth Технологічний аудиТ Та резерви виробницТва -№ 6/1(38), 2017 ISSN 2226-3780 metal hydroxides (aluminum, magnesium), which release water at temperatures of 190-270 °C and protect the surface at the initial stage of heating [8,9].Mineral fillers are nontoxic, effective and relatively inexpensive, which increases the interest for their using as flame retardants.
The composition of most developed fireresistant coa tings [10,11] contains in various proportions the compo nents of the intumescent complex and functional fillers, and as a binder either toxic resins or moisture resistant polymeric dispersions are used.
Nontoxic and waterresistant organosilicon resins are used infrequently [12], due to low adhesion strength, so it is promising to study the properties of fireresistant coatings based on silicones.
For the manufacture of samples fireresistant coating the experiment was planned with three variable parameters: х 1 -ammonium polyphosphate (NH 4 PO 3 ) n at n > 1000 content; x 2 -pentaerythritol C(CH 2 OH) 4 and melamine C 3 H 6 N 6 as threetotwo content; x 3 -magnesium hydroxide Mg(OH) 2 and aluminum trihydrate Al(OH) 3 as onetoone content.
Planmatrix of the experiment is listed in Table 1.-the common gas burner was used as a fixed source of flame (temperature); its capacity is 1.9 kW and flame temperature is under 1350 °С; -the experimental sample of fire resistant coating together with heat resistant glassfabric of 4 mm thick ness and steel plate of 0.25 mm thickness with overall dimensions are 150 × 150 mm was collected in a pack age.In the center of the heat resistant fabric and steel plate there was a square hole 70 × 70 mm for open flame access.The experimental samples of fireresistive coating were covered by a layer of heat resistant fabric and steel plate (Fig. 2).This way stacked sample to gether with the temperature measuring unit was fixed in a frame and was vertically mounted at the laboratory stand; -the temperature measuring (Fig. 3) unit is an outlet of 5 thermoelectric transducers 3 from the side not exposed to the flame; -the temperature on the surface of the fireresistant coating was monitored by one thermoelectric trans ducer 4 (type K).The readings of all thermoelectric sensors during the tests were registered in an automatic mode and processed electronically using a measuring complex (Fig. 3); -the temperature on the surface of fireresistant coat ing of the experimental samples was kept at the level of 600 ± 30 °С, duration of testing was 15-16 minutes, at the mean.This set of equipment allows to give a comparative evaluation of the fireproof properties coatings of various compositions.

research results
The photo exposures of samples surface changes due to swelling when exposed to an open flame in the course of experiments were made (Fig. 4).The thickness changes (Fig. 5) and the swelling coef ficients of fireresistant coating (a relative increase in thick ness) were established in the course of the experiments.The swelling coefficient was calculated by the formula: where t f -coating thickness after experiments, mm; t scoating thickness before experiments, mm.The swelling coefficient of fire resistant coating for the sample batches is the range 29-52, at the mean (Table 2) and does not significantly depend on the composition.
Tests executed for 9 different compositions of fireresistant coating (Table 1) and 5 samples for each composition.Sta tistical processing of experimental results was carried out.
The main function of the response is the tempera ture (°С) on a back surface of experimental samples.The averaged values of the temperatures for each composition are shown in Fig. 6.The empirical response function T emp is approximated by a linear relationship with respect to the content of com ponents (parameters of variation) and supplemented with the work of factors to determine the optimal composition: , , , , ) , The correlation coefficient between the value calcu lated from the empirical formula (2) and the value of the temperature in the experiments is K(T emp ,T exp ) = 0.966.The graph of response function is shown in Fig. 7.
Experimental compositions of fireresistant coating showed good fireretardant properties.The temperature on a back surface of the sample during the tests did not exceed 160 °C at the mean, which is much lower than the temperature of destruction polymer insulation of electric wires.
The proposed simple test method makes it possible to give a comparative evaluation of the performance cha racteristics of fire resistant coating.
For the first 3-4 minutes of exposure to an open flame, the surface layers of fire resistant coating foamed, and the temperature on a back surface of sample diffe rent experimental compositions stabilized at 110-150 °C.It is marked that temperature on a back surface of sample decrease with increasing content of ammonium polyphosphate (and correspondingly reducing the con tent of pentaerythritol and melamine), which is due to increased formation of phosphoric acids that act as flame retardants.At the same time, a decrease in the content of carboncontaining components led to a deterioration in the structure of coked cellular layer.
Aluminum and magnesium hydroxides actively remove heat at the first moment of heating the fireresistant coa ting at 190-270 °C, but do not give a significant effect of swelling.Their content in the composition should not exceed 10 %.
Based on the results of experimental studies of fire resistant coating, dependence was obtained: that adequately reflects the functional dependence of tem perature on a back surface of the sample from content of composition.
The coefficient of correlation between empiric depen dence (4) and the test results of samples of fire resistant coating was 0.966 that allowed defining the optimal con tent of composition.

swot analysis of research results
Strengths.Among strong parties of this research it is necessary to mark using for carrying out tests on the fire resistance of open flame of gas burner, as compared to tra ditional tests in a heat chamber that anymore corresponds to the terms of the real fire.
In favor of this statement is the fact that laborato ry tests in heat chamber can't recreate the conditions of a fire, as evidenced by an analysis of the modern world scientific periodicals on fire protection problems.More reliable test results can be obtained according to IEC 60332310:2000, when tests are carried out in test chambers equipped with gas burners.Technology audiT and producTion reserves -№ 6/1(38), 2017

ISSN 2226-3780
The properties of fire resistant coating in the experi ments were investigated, using relatively optimal ranges of concentration of fire resistant coating components, which made it possible to solve the problem of choosing a ra tional composition.
On the one hand the temperature on a back surface of the samples and structure of the formed foam coke, on the other hand, were the criteria for choosing the optimal components.
Weaknesses.The weaknesses of this study are related to the fact that the flame temperature of the gas burner during the experiments was not constant, in view of the gas flow reduction when the gas filling cartridge was used.Therefore, it was necessary to regulate the supply of gas in manual mode.In other words, the role of the subjective factor in the strict reproduction of experimental conditions for various experimental compositions of fire resistant coating is increasing.
At the same time, it is well known that under significant temperature differences on the front side of the coating, the thermochemical reactions between the coating compo nents can pass through different mechanisms, which can effect on the characteristics of the of fireresistant coating.
As a result, an error arises in determining the real relationship between the concentrations of the compo nents of the fireresistant coating and the flame retardant properties.
Opportunities.Further studies can develop in the direc tion of modification a silicone base to increase the adhesion properties of fireresistant coating, studying the interac tion between its components and optimize the formulation, taking into account the introduction of refractory fillers, dispersing and plasticizing additives.
Threats.The difficulties in implementing the results of the research are related to two main factors.
The first of them -only one brand of silicone resin was used in experiments to determine the optimal compo sition of fireresistant coating.It is well known that the mechanical and adhesive properties of silicone resins can vary over a wide range.Therefore, the results obtained in this study cannot automatically be extended to all of fireresistant coating with silicon resin.
The second factor -silicon resins are more expen sive, in comparison with traditional epoxy and phenol formaldehyde resins.The using of fireresistant coating with silicone resin can be justified for the protection of objects with an increased level of fire hazard.
Thus, SWOT analysis of research results allows to identify the main directions for the successful achievement of the research objective.Among them: 1. Modification of existing silicone resins to improve the adhesion properties of fireresistant coating to the surface to be protected.
2. Improvements of the proposed method for testing coatings for fire resistance, which will stability, support the influence of fire conditions (temperature and gas flow) during the whole experiment.

Conclusions
1. Influence of composition the fireresistant coating on the basis of organic silicon resin on fireproof proper ties was determined.The properties were estimated on temperature on back surface of experimental samples.It was established that the increasing of ammonium poly phosphate content from 55 to 65 % allows reducing the temperature on the on a back surface of the sample from 150 to 110 °C.
2. It was succeeded to reduce the toxicity of gases which generated by the action of an open flame on the fireresistant coating to the limited allowable concentra tions of 0.1 mg/m 3 of chlorine, 0.08-0.12mg/l of car bon oxide (II), 0.3 mg/m 3 of hydrogen cyanide.This was achieved by using the silicon resin that does not contain chlorine and nitrogen as a binder in the fireresistant coating composition.Demchenko V., simyachko е., svidersky V.

Introduction
The development of industry, especially in recent years, requires the creation of new building materials with improved properties.First of all, these materials must have increased strength, heat resistance, reduced thermal conductivity, as well as a lower cost in comparison with analogues present in the construction market of Ukraine.
With the development of scientific and technical prog ress, systematic identification of factors determining the operational properties and cost of building materials and, as a consequence, the potential possibilities of their regu lation become more and more urgent [1].
Significant interest in this direction is represented by ash microspheres.These are hollow ash pellets with an average size of 20 to 500 μm with solid, nonporous walls

a b fig. 2 .fig. 3 .
fig. 2. Experimental sample after fire resistance testing:a -in a fixing frame; b -disassembled

5 .
fig. 5.The thickness of the fire-resistant coating of different compositions after the experiments

2 )
where b 0 , b 1 , b 2 , b 12 -are unknown empirical coefficients; х 1 -relative ammonium polyphosphate content; х 2 -rela tive pentaerythritol and melamine as threetotwo content.The sum of squares deviations of empirical response function T emp from the average temperature in experiments for each experimental composition was adopted as target function Dtarget function D was perfor med using the standard Minimize function in MathCAD 14 program.As a result of minimization, the values of the empiri cal coefficients for (2) are obtained: b 0 = 535; b 1 = -845; b 2 = -1624; b 12 = 3275.

1 - 6 .
fig. 6.The dependence of temperature change on a back surface of the sample from the time: а -Composition 1; b -Composition 2; c -Composition 3

7 .
fig. 7. The dependence of temperature on a back surface of the sample from content of composition

table 1
Plan-matrix of the experiment for determining the optimal composition of fire-resistant intumescent coating