DOI 10.1007/s11148-017-0082-3 Refractories and Industrial Ceramics

Vol. 58, No. 2, July, 2017

HEAT AND SOUND INSULATION MATERIAL PREPARED USING PLANT RAW MATERIAL V. G. Babashov,1,2 A. S. Bespalov,1 A. V. Istomin,1 and N. M. Varrik1 Translated from Novye Ogneupory, No. 3, pp. 173 – 178, March, 2017.

Original article submitted January 25, 2017. Results are given for a study of parameters for preparing low density flexible fibrous material based on mineral fibers using plant fiber. The effect of amount of plant fiber (flax fiber – cottonized fiber) on material density and flexibility, prepared by aeration precipitation, and also the effect of binder based on plant raw material and facings on the main properties of flexible heat insulation materials are studied. A process is described for adapting production parameters applied to manufacturing material in pilot plant equipment in the FGUP VIAM branch in Voskresensk. On the basis of research results compositions and production principles are developed for manufacturing low-density heat insulation fibrous material. Keywords: heat insulation fibrous material, mineral fiber, quartz fiber, flax fiber, aeration deposition, sulfomethyl cellulose.

countering extreme heating during ignition is an important task in creating materials for prospective aircraft. Over the extent of many decades development has been carried out for fiber heat and sound insulation materials for airframe construction, and the first of them was quilted material based on cotton and reindeer wool, i.e., ATIMKh and ATIMO. The main disadvantages of these materials are very low application temperature, inflammability, and smoke release. In order to overcome inflammability it is necessary impregnate these materials with fire-retardant that led to an increase in hygroscopicity and corrosion activity, when material density reached 50 kg/m3. A considerable achievement was development of heat and sound insulation material VT4 with density of 55 kg/m3 from staple capron fiber. Later by loosening it and introducing polyamide adhesive material VT4S was prepared with density of 25 kg/m3. However, use of organic fibers of plant and animal origin did not make it possible without special impregnation to prepare non-hygroscopic and non-combustible heat and sound insulation materials. Then very light heat and sound insulation material ATM-1 was developed with density of 10 kg/m3 for the body and cabin of all types of aircraft. Its disadvantage was considerable water absorption. The problem was resolved by creating hydrophobic material ATM-1M whose water absorption was reduced by a factor of 20 due to spraying the glass mat with hydrophobic binder during glass fiber coating [8].

INTRODUCTION A complexity of civil aviation engineering is the ever increasing requirement for safety and level of passenger comfort, a reduction in specific fuel consumption and increase in engine specific thrust requires adoption of new structural solutions and creation of a contemporary or advanced contemporary engineering level of space vehicles (SV). Solution of the problem of communication on the Russian scale requires a significant fleet of aircraft of various types and classes, and organized production systems. A considerable role in resolving these problems is aviation materials science [1 – 7]. It is necessary to create new structural composites, nonferrous and heat-resistant alloys, contemporary functional materials exhibiting breakthrough properties and answering contemporary specifications laid down by SV builders [4]. Of special importance is development and introduction of new materials in a plan for resolving import substitution problems [1]. In contemporary domestic developments of civil aviation technology the proportion of imported materials often exceeds 70%, which leads to dependence of domestic manufacturers for supply from overseas. Provision of reliable operation of heat insulation under cyclic thermal loads and vibration, and also the possibility of 1 2

FGUP VIAM GNTs RF Moscow, Russia. [email protected]

208 1083-4877/17/05802-0208 © 2017 Springer Science+Business Media New York

Heat and Sound Insulation Material Prepared Using Plant Raw Material Research performed by authors of the present article was a step towards creating manufacturing technology for domestic heat and sound insulation materials capable of replacing those used previously in civil aviation for heat and sound insulation of aircraft cabins ATM-1 with good water absorption and ATM-1M whose output has recently ceased. This work also made it possible to provide import substitution of Microlite AA blanket material based on borosilicate glass fiber, produced by Johns Manville, USA (www.jm.com) and exhibiting the greatest demand in contemporary aviation industry. Work for creating highly thermally stable materials designed for prolonged service at high temperature have obtained new thrust in development with creation of high-temperature fiber based aluminum, silicon, and zirconium oxides [9 – 12]. These materials are especially in demand as heat insulation of high-temperature industrial units in field production and energy industries. Aircraft heat insulation normally operates in a regime in the range from –50 to +110°C. With cyclic heating and cooling it is especially important to avoid extreme moisture collection by heat insulation materials that leads to a marked weight increase. In addition, aircraft insulation should answer rules for fire safety. Fire resistant properties: low smoke release, capacity for damping during ignition, countering burn-through and penetration of heat flow should correspond to contemporary aviation rules. Research for creating new materials for insulation of aircraft cabins is carried out actively in all developed countries of the world. A review of scientific and technical, and patent information in the field of preparing flexible heat and sound insulation fire-resistant materials of low density has revealed the following trends: materials used currently for heat and sound insulation purposes are fiber mats, as a rule of lightweight fire-resistant fiber, often glass fiber, including hydrophobic fiber. A promising area for preparing low-density fiber heat and sound insulation materials with a high working temperature is creation of hybrid materials combining heat-resistant inorganic (quartz, silica, mullite-silica, and aluminum oxide) and low-density organic (flax, cotton) fiber, binder thermoplastic fibers, and also fire-resistant and endothermic fillers. Plant fibers, i.e., cellulose, flax, cotton, and cottonized, are hardly non-hygroscopic. The structure of a plant fiber is capillary, i.e., a fiber is hollow in a conditions absorb moisture. This is connected with movement feeding substances in plants. The process of moisture diffusion in a plant fiber only proceeds within capillaries, keeping the space between fibers dry, whereas for example in glass or mineral fibers moisture condenses between fibers lowering heat insulation thermal conductivity. A disadvantage of plant fibers is their inadequate resistance to ignition at high temperature. Due to a hollow structure of plant fibers exhibits low density, and in addition the cost is low. Therefore currently fibers of plant origin after required treatment are used for preparing heat and sound insulation materials for various purposes. In a patent of an American company Unifrax [13] a multilayer

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flameproof heat insulation is proposed, including a layer of heat-resistant organic fiber and a layer of endothermic filler. Each of these layers may contain organic or inorganic binder. These heat-resistant organic binders may be polycrystalline fiber based on Al2O3, mineral wool, glass, quartz fiber, or a mixture of them. The binder may be organic or inorganic. Thermally hardening organic fibre, which retains flexibility after hardening, may be selected from a groups containing latex, styrene, and butadiene copolymers, acrylonitrile, polyurethane, polyamides, silicones, and other resins. The inorganic binder may be used alongside organic binder, or instead of it. This may be colloidal oxides of silicon, aluminum, zirconium, or a mixture of them. The endothermic filler proposed is hydrated inorganic materials such as aluminum oxide hydrate, zinc borate, calcium sulfate, etc. Fireproof heat insulation may be made both stiff and flexible. It may be prepared by vacuum molding from aqueous fiber suspensions. Another method of improving heat insulation and fire-resistance properties of material with retention of low density is use within the composition of heat insulation of organic materials capable of charring under action of temperature and serving as a barrier for flame propagation, and also thermally expanding materials. An example of this is flexible heat- and fire-resistant material offered by the British Technology Group [14]. The material contains organic and inorganic fibers and also organic thermally expanding filler that makes it possible to retain flexibility and thermal shock resistance in a working temperature range up to 500°C, and also to withstand action of flames and temperature up to 1200°C for up to 10 min. Organic fibers contained in this material should be subjected to special treatment with a substance retarding combustion in order that the carbonization reaction prevails over mechanical degradation. Developers of the material explain that with combined charring of organic fiber and expanded filler in the range from 200 to 500°C the fiber surface is wetted by liquid acid substances of decomposing expanded filler. As a result of this a strengthened fibrous amorphous structure is created with carbon bonds facilitating further expansion. Above 500°C oxidation of carbon in air commences at the surface and propagates inwards at a rate depending on oxygen diffusion rate in the structure. In this case within the hybrid material heat-resistant organic fiber present in hybrid composite material delays complete carbon oxidation of the material for a period from 2 to 10 min up to 1200°C. Inorganic fiber forms a framework structure that retains the properties of heat insulation even after complete gasification of all carbon-containing components in the material. A facing of nonwoven material has been proposed by the authors made from organic cloth subjected to fireproof treatment, for example from cotton treated with phosphorus- and nitrogen-containing combustion retardants or a network of Visil. Flexible fireproof heat protection material according to this invention may be constructed in accordance with specifications for a specific application, i.e.,

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V. G. Babashov, A. S. Bespalov, A. V. Istomin, and N. M. Varrik

Fig. 1. Material specimens based on basalt fiber (a), cottonized fiber (b ), quartz fiber (c) and a mixture of three fiber types (d) prepared by aeration deposition.

to have a previously prescribed density, thickness, and maximum working temperature. As a result of analyzing scientific publications it is clear that the main trends in development of this class of materials are a reduction in heat insulation weight, improvement of heat and fireproof qualities, and a reduction in cost. The core use for heat insulation is fibrous or foamed flexible materials whose operating temperature may vary from 400 to 1100°C, depending on operating conditions. Heat insulation has a water-resistant shell, as a rule of polymer films, and also an additional layer of protective material providing heat insulation strength and fire resistance. Binder within the heat insulation composition should provide flexibility, hydrophobicity and exhibit flame resistance. A reduction in heat insulation density is implemented by introducing into the composition of fibrous heat insulation lightweight fibers of plant origin. In order to improve fire resistance new forms have been developed of highly heat-resistant fibers and also protective coating answering contemporary specifications for aviation regulations. Fire resistance of a heat insulation system is increased due to introduction into a polymer shell of a heat insulation system of layers resistant to combustion, such as reflecting high-temperature mineral (for example, vermiculite), metal foil, high-temperature paper based on refractory fiber oxides. The increased working temperature of heat insulation is achieved due to use of highly heat-resistant fibers and creation of hybrid thin-layer composites, combining high-temperature oxide fibers and flexible polymer materials. A reduction in material cost is achieved due to use of inexpensive starting materials during preparation of fiber mats for heat insulation, and also organization of large-scale production.

MATERIALS AND RESEARCH METHODS From results of analyzing information the main starting components selected for fiber mat were mineral fibers (based on fiber material BUTV, quartz fiber grade TKV), cottonized flax fiber, cellulose sulfoester as a binder component prepared by treating flax fiber, and emulsion of polyvinyl acetate and polyester fiber, and for facing material quartz canvas grade KhKV and silica cloth grade KT-É-105. Preliminary experiments were conducted in a Niro Atomaizer spray drier using a nozzle for creating a stream of air and a non-standard unit for preparing flexible heat insulation. A series of studies was carried out in pilot plant equipment. RESULTS Specimens of low density heat insulation fiber material (Fig. 1) were prepared with aeration deposition by spraying fiber in a stream of compressed air (air pressure 6 atm). Research was carried out using the following fiber components: polyvinyl acetate emulsion (1% water), cellulose sulfoester (2% aqueous solution), and polyester fibers. The binder component was introduced into specimens of heat and sound insulation by aeration deposition based on a mixture of organic (cottonized flax) and inorganic (basalt BUTV and quartz TKV) fibers during deposition of a fiber mat and after deposition by means of a sprayer (for liquid component). After adding binder fiber mat specimens were heat treated: with polyvinyl emulsion at 80°C, with cellulose sulfoester at 100°C, and with polyester fibers at 180°C). The dependence of specimen density on form of binder components was studied. Specimens with different forms of binder are shown in Fig. 2. The density of experimental heat insulation fiber material specimens compared with analogs is given in Table 1.

Heat and Sound Insulation Material Prepared Using Plant Raw Material

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Fig. 2. Material specimens prepared using polyvinyl acetate emulsion (a), sulfoester cellulose solution (b ), and polyester fiber (c).

DISCUSSION OF RESULTS Test results showed that experimental specimens of heat and sound insulation fiber materials using as binder components polyvinyl acetate emulsion, cellulose sulfoester, and polyester fibers, introduced during molding of fiber mat or after molding, prepared by aeration deposition, with respect to density index are at the level of domestic (ATM-1) and overseas (Microlite AA blanket) analogs. However, specimens with polyester fiber were inadequately uniformly mixed during deposition of fiber mat. This led to uneven stabilization of fiber mat in such a way that there was material breakage in those areas where polyester fiber was absent. Specimens with soluble binder component (polyvinyl acetate emulsion and cellulose sulfoester), introduced after fiber mat decomposition, were stratified since the fiber was not distributed throughout the whole fiber mat volume. Therefore, the most effective methods were acknowledged as those introducing dissolved binder in liquid form (emulsion or solution) during fiber mat molding. In subsequent research it made sense to use the more effective methods of material fiber separation. Specimens of fiber material based on a mixture of organic (cottonized flax) and inorganic fibers (basalt grade BUTV and quartz grade TKV) were prepared with a more effective binder component, i.e., cellulose sulfoester. Composition of specimens: quarts fiber TKV 50%, cottonized material 50%; quartz fiber grade TKV 20%, basalt fiber grade

BUTV 70, cottonized fiber 10%; quartz fiber TKV 70, basalt fiber grade BUTV 20%, cottonized fiber 10%. Specimens were prepared in pilot plant equipment in FGUP VIAM. Results of studies are given in Table 2. It was established all specimens of heat and sound insulation materials of different compositions prepared by aeration deposition using cellulose sulfoester as a binder component, added during fiber mat molding, are at the level of domestic and overseas analogs with respect to density and flexibility, and have a high value of elasticity Use of the material is planned in civil aviation. Operating conditions assume a working temperature from –60 to +110°C and short-term up to +1200°C in the case of fire, and therefore the main material developed should be high-temperature quartz fiber grade TKV. As is seen from results of studies, specimens of different composition with respect to physicomechanical properties are at one level, and therefore the following composition of flexible heat and sound insulation fibrous material is determined as the optimum: quartz fiber TKV 70 – 80%; basalt fiber BUTV 10 – 120%; cottonized flax fiber 5 – 10%. Physicomechanical properties (density, flexibility, elasticity) have been determined for specimens of low density of optimum composition (starting material). Changes have been studied in physicomechanical properties of material after thermal action, typical under operating conditions (Table 3). Analysis showed that experimental specimens after action of temperature in the range from –60 to +110°C with respect to density and flexibility

TABLE 1. Density of Heat Insulation Fiber material Experimental Specimens Compared with Analogs Sample No.

Specimen main material

Binder

Binder introduction method

Density, kg/m3

1

Quartz, basalt, cottonized flax fiber

Polyvinyl acetate

During deposition of fiber mat

11.5

2

Mixture of quartz, basalt, and cottonized flax fiber

Polyvinyl acetate

After deposition of fiber mat

8.2

3

Mixture of quartz, basalt, and cottonized flax fiber

Sulfoester cellulose

During deposition of fiber mat

9.9

4

Mixture of quartz, basalt, and cottonized flax fiber

Sulfoester cellulose

After deposition of fiber mat

9.5

5

Mixture of quartz, basalt, and cottonized flax fiber with polyester fiber

None

During deposition of fiber mat

7.6

6

Domestic analog, i.e., fibrous heat-insulation material ATM-1

—

—

10.0

7

Overseas analog, i.e., fibrous heat-insulation material Microlite AA blanket

—

—

9.6

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V. G. Babashov, A. S. Bespalov, A. V. Istomin, and N. M. Varrik

TABLE 2. Physicomechanical Properties of Heat and Sound Insulation Fibrous Material Specimens Compared with Analogs Sample No.

Density, Flexibility, Elasticity, kg/m3 mm %

Specimen, composition

1

Quartz 50%, cottonized fiber 50%

12.5

100

88

2

Quartz 20%, basalt 70%, cottonized fiber 10%

11.2

100

88

3

Quartz 70%, basalt 20%, cottonized fiber 10%

12.0

100

87

4

ATM-1

10.0

—

—

5

Microlite AA blanket

9.6

—

—

TABLE 3. Physicomechanical Properties of Heat and Sound Insulation Fibrous Material Specimens of Optimum Composition after Action of Temperature Sample No.

1

Specimen

Original

Density, kg/m3

Flexibility, mm

Elasticity, %

12.0

100

87

After action of temperature, °C 2

–60

11.6

100

85

3 4

+110

11.8

100

97

+1200

19.5

300

64

TABLE 4. Density of Experimental Facing Specimens of Heat and Sound Insulation Fibrous Material Compared with Analogs Sample No.

Facing type

Facing fastening method

Density, kg/m3

1

Canvas KhKB

By means of polyvinyl acetate emulsion

14.1

2

Canvas KhKB

Stitching with continuous quartz thread

14.8

3

Cloth KT-É-105

By means of polyvinyl acetate emulsion

17.3

4

Cloth KT-É-105

Stitching with continuous quartz thread

17.8

are at the level of an original specimen, and also domestic and overseas analogs, and have a high elasticity value, and after short-term action at 1200°C they retain their integrity. A facing coating was selected for flexible heat and sound insulation fiber material. A coating should have a low surface density, increased heat resistance, and provide high adaptability for fiber material (facing material should have good flexibility and production strength). Experimental specimens have been prepared of flexible heat and sound insulation fiber material of low density, facing canvas, and silica cloth by

two methods: by means of 1% solution of polyvinyl acetate emulsion and a method of stitching fiber material with a continuous quartz thread grade KS-11-17´1´2 (linear density 68 tex). The density of experimental facing specimens of heat and sound insulation material are given in Table 4. Research results have shown that experimental specimens of faced flexible heat and sound insulation fiber material have density greater by a factor of 1.2 – 11.7 compared with unfaced specimens and with good adaptability. Facing coatings of flexible heat insulation fiber material have been selected with quartz canvas grade KhKV since by means of this it is possible to prepare material with the least density. The material obtained contains mineral fibers as a base, fibers of plant origin and organic binder, and the material density is not more than 15 kg/m3. The authors thank colleagues of the FGUP VIAM A. S. Bondarenko and O. A. Nazarov for help in performing experiments. REFERENCES 1. E. N. Kablov, “Innovative development of FGUP VIAM GNTs RF for implementing “Strategic direction for development of materials and processing technology for the period up to 2030,” Aviats. Mater. Tekhnol., No. 1 (34), 3 – 33 (2015). 2. E. N. Kablov, “Materials for Buran objects – innovative solution f formation of the sixth technological mode.” Aviats. Mater. Tekhnol., No. S2, 3 – 10 (2013). 3. D. V. Grashchenkov, B. V. Shchetanov, E. V. Tinyakova, and T. M. Shcheglova, “Possibilities of using quartz fiber as a binder in preparing light-weight heat protective materials based on Al2O3 fiber., Aviats. Mater. Tekhnol., No. 4, 8 – 14 (2011). 4. E. N. Kablov, “Russian requirements for new generation materials,” Redkie Zemli, No. 3, 8 – 13 (2104). 5. E. N. Kablov and B. V. Shchetanov, “Fiber herat insulation and heat protective materials: properties, fields of application,” Proc. Internat. Sci.-Tech. Conf., “Fundamental problems of high-speed flow,”hukovskii, 21 – 24, September, 2004. 6. Yu. A. Ivakhnenko, V. G. Babashiv, A. M. Zimichev, and E. V. Tinyakova, “High-temperature heat insulation and heat protection materials based on refractory compound fibers,” Aviats. Mater. Tekhnol., No. S, 380 – 385 (2012). 7. E. N. Kablov, B. V. Shchetanov, Yu. A. Ivaknnenko, and Yu. A. Balinova, “Prospects of reinforcing high-temperature fibers for metal and ceramic composite materials,” Trudy. VIAM: Elektron. Nauch.-Tekhn. Zh., No. 2, Art. 5 (2013). URL: http://www.viam-works.ru (access date 03.21.2016). 8. Aviation Materials: Handbook in 12 Vol. Vol. 9, Heat Protection, Heat Insulation and Composite Materials, High-Temperature and Nonmetallic Coatings [in Russian]. VIAM, Moscow (2011). 9. V. G. Babashov and N. M. Varrik, “High-temperature flexible fiber heat insulation materials,” Trudy. VIAM: Elektron. Nauch.-Tekhn. Zh., No. 1, Art. 3 (2015). URL: http://www.viamworks.ru (access date 03.21.2016). DOI: 10.18577/2307-60462015-0-1-3-3. 10. Yu. A. Ivakhnenko, V. V. Kuz’min, and A. S. Bespalov, “State and prospects for developing heat insulation fireproof materials,” Probl. Bezopas. Poletov, No. 7, 27 – 30 (2014).

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