Modern scientific and practical tendencies in fire protection

S. A. Nenakhov, V.P. Pimenova.  Review of publications of 3rd Berlin conference. Journal "Paintwork Industry" № 7, 2009

The third annual conference on flame retardants (Fire Retardant Coatings III) took place in Berlin during 18-19 September 2008. Twelve papers were presented at the conference. Speakers were professionals known in the field of science and technology (Serge Burbizho, etc.). The overwhelming majority of speakers were from Germany (5 reports), and the rest - from France, Britain, Turkey, Brazil and Switzerland. Six reports were introduced by employees of the institutes and universities, six others - by employees of governmental research centers and research centers of private companies.

The third annual conference on flame retardants (Fire Retardant Coatings III) took place in Berlin during 18-19 September 2008. Twelve papers were presented at the conference. Speakers were professionals known in the field of science and technology (Serge Burbizho, etc.). The overwhelming majority of speakers were from Germany (5 reports), and the rest - from France, Britain, Turkey, Brazil and Switzerland. Six reports were introduced by employees of the institutes and universities, six others - by employees of governmental research centers and research centers of private companies.

 
Apart from speakers, 54delegates from Europe, North and South America and Asia attended at a conference. The largest number of delegates - 17 - were from Germany, the second multiplicity of command - from the Netherlands, as well delegates came from Asian countries (UAE, Malaysia) and one delegate from Russia (A Company B, Moscow). Generally delegates were representatives  the of various industrial companies: International Paint Ltd, Baril Coatings BV, Sika Deutschland GMBH, 3M Deutschland GMBH, Budenheim Iberica SLSC, AMONN FIRE srl, PPG Industries Netherlands BV, Akzo Nobel Aerospace Coating BV, BASF SE, Teknos Oy, Leighs Paints, Neokem SA and others (about 40 different industrial companies).

Reports presented at the III European Conference were divided into three sections:
I - Mechanism of flame retardant action and testing; II - New fire-retardant materials and technologies; III - Developments in phosphorus-containing flame inhibitors.

Conference was preceded, as it is customary nowadays, by a four hour teaching introduction to the basic concepts of fire retardant properties of materials, the inhibitory effect of various chemical compounds, intumestsent coatings, safety and operational standards. Introductory lectures were read by experts from Clariant Produkte GmbH (Germany), Adrian Bird (Adrian Beard) and Walker Tyuz (Volker Thewes).


SECTION “MECHANISM OF FIRE RETARDANT EFFECT AND TESTING”

In the report of Bernard Shartel¹ FROM “BAM - Bundesamt fur Materialforschungund prufung” (Berlin, Germany) the problem of mechanism of action of flame retardants is regarded as a problem of interrelated physical and chemical processes occurring on coating of the surface covering the flammable plastic substrate. The way of describing flows of matter and heat through this surface was discussed, which is of undoubted interest from the standpoint of a kinetic model of foaming fire retardant coatings, taking into account all the processes and characteristics of coatings and the power of external heat fluxes. The report also provides information about global sales of retardants (inhibitors, flame retardants): so according to submit data in 2001, sales totaled 1.97 million U.S. dollars (Img. 1). Fire retardant in terms of sales form the following series: bromine compounds> organophosphorus compounds> oxides of antimony> aluminum trihydrate> other> chlorine compounds.



Img 1. Value of world sales of various inhibitors of firing in 2001

Report of Serge Burbeageau with Sophie Ducousin from the National High School Chemistry (Lille, France) dedicated to the development of laboratory methods for testing fire-resistant coatings on steel, wood, textiles, or, as the author calls these test methods - small scale tests or (compact) test. Such work is necessary, as indicated in the report, due to the fact that large-scale (full-scale, bench) testing are expensive and time consuming. The report hereafter describes the plant (Img. 2) to test any of these substrates with the dimensions of the sample 5x5 cm and a thickness of 2 to 10 mm with an external heat source with constant temperature and the typical experimental plots. At the same Img 2 is a furnace for industrial testing.

         
                                                          a                                                                                             b
Img 2. A device for laboratory tests of fire resistance (a) and industrial test furnace (b).

It should be said that this kind of technique, even more perfect, since it calls for heating of the sample in the "standard" fire has existed in Russia since 1998. Of course, manufacturing companies have some of their own laboratory techniques, but usually it is their know-how, and therefore obtained data were and are virtually inaccessible to generalization. The development of Burbizho is designed to fill this gap. Next, testers will inevitably have to deal with problems of regulatory of the thermal regime, questions of correlation of field and laboratory tests and other issues.
Consideration of the influence of weather factors on the fire-retardant coatings, operated in the open atmosphere, presented in the report of Barbora Deppe and colleagues from the company WKI - Fraunhofer-Institute for Wood Research-Wilhelm-Klauditz-Institut (Braunschweig, Germany) continues the subject, raised by other past Berlin conferences. The urgency of the problem is that even the thick-layer, for example, acrylate coating considered in this report (2 mm or more), working well inside buildings, being handed down from the premises in an open atmosphere quickly lose their fire-retardant efficiency, while the fire protection of many technical installations outside is even more demanded than domestic protection. Company WKI in Braunschweig completed a many months exposure of coatings on the specially built full-scale testbed (Img. 3), followed by study of the behavior of coatings in the firing tests. It is curious that the authors are talking, including full-scale tests, of coatings on wood substrate. The authors studied, using scanning electron microscopy, the structural features of created protective shells for supplements (retardants). The authors report that in the case of protection (encapsulation) supplementation improves weather resistance of flame retardants, especially if they are embedded in the weather-resistant matrix, but this effect requires further investigation. Works in this direction have an unconditional practical interest for our country.
 

Img 3. Test climate stand for flame retardants in Braunschweig.

In the report of Dave Haytornvayt from the company Salamander Fire Risk Analysis (Lanks, UK) about the fire danger of multilayer decorative coatings in public buildings (hospitals, museums, libraries, theaters, etc.), the specificity of combustion of multilayer coatings is observed; for example, fires in the UK Over the past 25 years, show the need to improve the regulatory basis of framework and the possibility of fire protection of decorative coatings transparent flame retardants.
And finally, the last in this section was the report of Debbie Smith from BRE Global Limited (Herfordshir, UK), about the problem of evaluating the effectiveness of swelling coatings on modern steel structures; it was devoted to questions of appropriate methods of industrial (natural) tests in conditions of real fire on real modern steel structures. The authors write that the required level of fire protection of steel elements in any design, to prevent their destruction, is a function of the form and type of steel structure, being protected from fire. For traditional fire protection products, being used on solid steel sections, in the projects are widely used ratios, establishing the connection between the limiting temperature of steel and fire-protection time limits. These relations are based on the analysis of fire tests using statistical analysis or differential equations of heat. Proved that for swelling fire protective coatings, these historical test procedures and test methods are inadequate and should be improved. These products vary their thickness and shape during the process, which should be taken into account. Especially as modern methods of designing of steel structures create new problems. For instance, for each steel element within the overall structure may exist a different limiting temperature in the fire situation. Long-span beams can significantly deform during the fire, but the coating should not break down and lose adhesion due to the protected design.
Of course, the problem of compliance of any testing methodologies with real fire situation exists, it consists of several questions, chief among them – is appropriation of methods to real conditions, as well as informativity and relevance of test and calculation methods, so the emergence of studies and publications on the subject is not unexpected. Such questions are discussed in the national scientific and technical literature.
Thus, in the reports delivered at this conference session, as main issues under consideration, in our view, can be considered issues relating to the development of ideas about the mechanism of swelling of flame retardant coatings, development of laboratory testing methods for flame retardants and the problems of assessing the effectiveness of coatings on swelling on steel structures. Consideration of these issues at an international conference indicates that these problems are relevant in an international scientific and technical community, but the reports (objects, methods and findings) show that they are relevant primarily from a purely pragmatic point of view. Attendance at the conference of fifty delegates from various industrial companies from around the world in the year of the industrial crisis confirms the interest of industry to the issues being addressed, and their relevance.

SECTION "NEW FIREPROOF MATERIALS AND TECHNOLOGIES"

The report of Axel Kaleder from the company Inomat GmbH (Blizkastl, Germany) was dedicated to the development of fireproof materials of indoor and outdoor use, namely of inorganic silicate water-based paints, providing a slight separation in case of fire toxic substances. Among the advantages of these materials, the author notes the availability and cheapness of the main component – the water glass and the fact that a heat effect in such coatings is achieved by water evaporation and the formation of inorganic silicate foam. Among the drawbacks of inorganic materials he indicates: bad climatic stability, fragility, low adhesion to various substrates, the need for multiple layers in the coating, including priming protective layer. He also examines the advantages and disadvantages of materials on an organic binder. The idea of development was to create a hybrid of organic-inorganic material, combining the advantages of both kinds of materials and minimize the disadvantages of each type. As far as can be seen from the image (only images from the presentation are published, the text is missing), the technical solution is to apply nano-layer phenolic resin for grinding glass. Specifications are indeed worthy of attention – that is the material of low density (100 kg • m-3), with very low thermal conductivity (0,05 W • m-1 • K-1) with improved performance characteristics.
The report of Regina Nascemento et al from the State University (Rio de Janeiro, Brazil) considered the results of the application as modifiers of various polymer flame retardant systems of inorganic fine (nano) supplements (based on natural Brazilian clay, montmorillonite clay and model layered silicates with different interplanar distance in crystals). The following polymers were used: polypropylene copolymer, polyethylene and ethylene butyl acrylate with methyl acrylate. Results of experimental studies (TG, limiting oxygen index, microscopy, flow measurement, the measurement of flame retardant performance standard UL-94) have shown positive effects of additives in combination with standard intumestsent recipe, accompanied by synergism. It should be noted that the standard intumestsent recipe to plastic materials of the authors is a mixture of ammonium polyphosphate (Exolit 422) and pentaerythritol (from Sigma Aldrich) at a ratio of 3 to 1 (ie intumestsent supplement does not contain melamine). Important is the result of studying of the influence of structural parameters of the filler - clay. Very good results were obtained with the natural Brazilian clay. The study of various modeling clay showed that the clay with interlayer distance with the size to 22? produced the same synergistic effect as the natural clay (11.7 "). The results show that when the interval exceeds 22 between layers, then the clay begins to lose its synergistic effect. Results from the spent catalyst (taken with the installation of oil cracking with a fluidized catalyst, a catalyst usually consists of a zeolite embedded in a matrix of aluminosilicate, zeolites have a cavity size of no more than 12 5 A) confirm this model in terms of the importance of the maximum pore size for the synergistic effect. Unfortunately, in the published material, the authors do not express even the assumptions about the nature of the influence of the studied inorganic additives, limiting themselves with a statement of the role and the upper limit of the distance between planes in the crystallites of the filler in fire-resistant properties. Studies of the effect of fillers of various nature have shown that the effect of this type of fillers in the process of forming of foamcoke may lie in the nucleation and the endothermic effect, the first of which depends on the surface properties of filler, and the second changes due to the specific heat and the decomposition temperature.
The report of Aysun Tsirel from the University (Izmur, Turkey) is devoted to new technologies for fire protection of textile materials, namely, the sol-gel and plasma technologies. The author reports that treatment of cotton fabrics with phosphorus and silicon-containing additives on sol-gel method for non-combustibility allowed to improve fire-retardant properties of cotton fabric 2-3 times when handling tetrametildisiloxsan tissues. Sol-gel coating can be an alternative for flame retardant thin films. He also reported that work is underway to enhance the synergy effect of phosphorus and boron on cotton fabric coated with a thin silica film by sol-gel technology.
Reaction oligomers as surface modifiers of magnesium hydroxide, which is one of the active components of flame retardant materials, are considered in the report of Elisabette Ranucco et al from the Department of Organic Chemistry, University of Milan (Italy). Magnesium hydroxide is widely used in flame retardant materials based on polypropylene, and its amount in the composition reaches 50 wt%, which creates difficulties in the preparation of compositions and extrusion processing of them into products. Surface treatment of Mg (OH) 2 by stearic acid improves processability and mechanical properties of the compositions, but on the other side its fire-retardant properties are reduced. The authors report that for solution of  this problem, they studied the possibility of using new reactive oligomers as surface modifiers for magnesium hydroxide and their effect on workability and dispersibility of the filler, mechanical properties and flame retardant properties of Mg (OH) 2/polipropilen tracks. Reactive oligomers were obtained by radical copolymerization in solution of tretbutilperoximetilhexen, butyl acrylate and maleic anhydride. Tretbutilperoximetilhexen was previously synthesized by the method of Yurchenko. It was shown that used modifiers improve the dispersion of magnesium hydroxide, improve processability, even at 60% filling. Mechanical properties of flame retardant products improved without loss or even with the improvement of fire retardant properties.
Thus, summarizing the papers presented at this purely Materials Research section of the conference, we can state that it considered three kinds of fireproof materials: hybrid organosilicate compounds, fabric and extruded polyolefin materials, more precisely, questions of  improving the quality of these materials by selecting the filler, and methods of surface treatment. Of course, the data are of interest and can be used in relation to the materials of various kinds. Roll retardants (fabric-based or based on polyolefins) in Russia are not being produced; this niche has yet to be filled.

SECTION “ELABORATIONS IN THE FIELD OF PHOSPHORUS FLAME INHIBITORS”

Manfred Doering from the Institute of Technical Chemistry (Egenshtayn Leopoldshafen, Germany) at the beginning of the report notes that the recently-modified epoxy resins with phosphorus have already found industrial application as flame retardants in printed circuit boards and laminate. Different phosphorus compounds including phenanthrene are well performed. In this paper are contained two different approaches to obtaining the modified phosphorus epoxy materials (based on Novolak resins DEN 438 and dicyandiamide). The first research considers non reactive derivatives of phosphocycles. The second - reactive adducts of aldehyde dihidrophosphophenanteoxid and dimetilfenoksifosfinoksid (as a hardener diaminodifenilmetan was used). It is shown that these materials have reached a good enough fire resistance, with evaluation of V0 (the third degree of stability - no burning falling drops) per UL 94 at low phosphorus concentrations (0,6 - 1,4% P) and high glass transition temperatures (Tg = 180 - 190 0C), but by a number of indicators the authors prefer non reactive additives.
The report of Sabayasashi Haan et al from EMPA (the San Gallen, Switzerland) discussed the application of organophosphorus inhibitors (retardants) in the cellulose and other synthetic polymers. It is noted that of particular interest are organophosphorus compounds in combination with nitrogen because of possible synergies. Recently developed by the authors phosphorus amide compounds being synthesized from cheap products (trimethyl phosphate, triethyl phosphate and dietilfosforamid) in good yield, have shown encouraging results.
The report of Helena Dzhurdzhevich from Laksness Deutschland GMBSH (Dormagen, Germany) was dedicated to firing inhibitors on the base of phosphorus for transparent varnishes. This discourse is about modification of transparent varnish liquid phosphorous inhibitors with preserving the properties of decorative coatings; it has been shown that they provide a good flame retardant effect, not falling along with that under the European Directive 2004/42/EC of the solvents. Some components (organic phosphate, phosphonate and phosphinate salt) are solid particles ranging from white to beige. Crystal triphenyl melts at a temperature of 49 0C. The melt has a very low viscosity and reported a small plastics plasticizing effect. Overall, the authors worked over a wide range of binders, inhibitors, curing agents, solid additives. So among liquid organic phosphorus compounds were studied: triethyl phosphate, trihlorpropilphoosphat, krezildifenilfosfat, dimetilpropilphosphat, tricresyl phosphate, and triphenyl dipheniloctylphosphat. It is shown that these compounds may be no less effective than traditional hard inhibitors (ammonium polyphosphate, aluminum oxide, aluminum trihydrate, a product Bayfomox ® WMP on the basis of nitrogen and phosphorus), and varnishes thereat are retaining their transparency.
Thus, the papers read in this section of the conference were focused mainly on studying of the effectiveness of different phosphorus-containing fire inhibitors (retardants), used directly in the polymer compositions with improved own fire resistance. Among these inhibitors are considered: phosphocucly, reactive adducts, phosphorus amide compounds, low molecular weight liquid phosphates. Such fire-resistant polymers find wide application in areas where the use of flame retardants is difficult for one reason or another.

CONCLUSION

The third Berlin Conference devoted to flame retardants, as well as previous ones, was focused solely on applied problems of fire protection, not for nothing that it is visited mainly by representatives of generating companies from all continents. Purely scientific issues (the problem of describing of the front propagation reactions and other physical and chemical problems) are treated at other conferences and in several different audiences. This conference focused on four groups of issues: (1) mechanisms of action of flame retardants and external climatic factors effect on the flame retardant properties, (2) methodological issues of testing of fire-resistant properties, (3) the adequacy of assess of fire-resistance rating in application to complex structures, (4 ) materials science aspects of the modification of flame-retardant coating and of improve the fire resistance of polymers.
Obviously, such a pragmatic orientation of the conference is demanded by practice and is fully supported by the publisher VINCENTZ, under whose auspices these conferences are held. As the publisher VINCENTZ informs, it selects the reports by the criteria of urgent technical need, urgency of the problem. Regularity of conferences, the repertory of the audience and the number of delegates indicates that this is in point of fact. On the conference are being heard reports on the most pressing technical issues of fire protection, their high scientific level and substance give the possibility of expanding the circle of knowledge by professionals working in this issue: materials scientists and technologists. Of course, this knowledge still needs to be able to use it. 
Materials placed in the collection adequately reflect the level of progress of overseas developments in the field of fire protection. For this reason alone they can be of interest for Russian specialists.

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