Expanded polystyrene: foamed and extruded

Expanded polystyrene Suspension Pressless Self-extinguishing (PSB-S) on a cut (EPS)

The structure of expanded polystyrene at high magnification
Pénopolistirole

is a gas-filled material obtained from polystyrene and its derivatives, as well as from styrene copolymers. Expanded polystyrene is a widespread type of polystyrene, which is usually called in everyday life. The usual technology for producing expanded polystyrene is associated with the initial filling of styrene granules with gas, which is dissolved in the polymer mass. Subsequently, the mass is heated with steam. In the process of this, a multiple increase in volume of the original granules occurs until they occupy the entire block shape and are not sintered together. In traditional expanded polystyrene, natural gas, which is readily soluble in styrene, is used to fill the granules; in fire-resistant versions of expanded polystyrene, the granules are filled with carbon dioxide [1]. There is also a technology for obtaining vacuum expanded polystyrene, which does not contain any of the gases.

Content

• 1 History of the production of expanded polystyrene
• 2 Composition of expanded polystyrene
• 3 Methods of obtaining
• 4 Properties of expanded polystyrene
• 5 The main types of produced polystyrene foam
• 6 Application
• 7 Properties of expanded polystyrene 7.1 Water absorption
• 7.2 Vapor permeability
• 7.3 Biological stability
• 7.4 Durability
• 7.5 Resistance to solvents

The history of the production of expanded polystyrene

The first expanded polystyrene was produced in France in 1928 [2]. Industrial production of expanded polystyrene began in the 1937s. [specify

] in Germany [3]. In the USSR, the production of expanded polystyrene (grade PS-1) was mastered in 1939 [4], grades PS-2 and PS-4 - in 1946 [5], grade PSB - in 1958 [6] In 1961, the USSR mastered the technology for the production of self-extinguishing expanded polystyrene (PSB-S) [7]. For construction purposes, PSB expanded polystyrene began to be produced in 1959 at the Stroyplastmass plant in Mytishchi.

Composition of expanded polystyrene

To obtain expanded polystyrene, polystyrene is most often used. Other raw materials are polymonochlorostyrene, polydichlorostyrene, and copolymers of styrene with other monomers: acrylonitrile and butadiene. Low-boiling hydrocarbons (pentane, isopentane, petroleum ether, dichloromethane) or blowing agents (diaminobenzene, ammonium nitrate, azobisisobutyronitrile) are used as blowing agents. In addition, the composition of expanded polystyrene boards includes fire retardants (flammability class G1), dyes, plasticizers and various fillers.

Methods of obtaining

A significant proportion of the obtained polystyrene foam is produced by foaming the material with vapors of low-boiling liquids. For this, a suspension polymerization process is used in the presence of a liquid that can dissolve in the original styrene and is insoluble in polystyrene, for example, pentane, isopentane, and their mixtures. In this case, granules are formed, in which the low-boiling liquid is evenly distributed in the polystyrene. Further, these granules are subjected to heating with steam, water or air, as a result of which they significantly increase in size - 10-30 times. The resulting bulk granules are sintered with simultaneous molding of products.

Properties of expanded polystyrene

High quality expanded polystyrene: material with evenly spaced granules of the same size

Low-quality expanded polystyrene of the PSB type: a break occurs along the contact zone of balls of different sizes
Expanded polystyrene, which was obtained by foaming a low-boiling liquid, is a material consisting of fine-cellular granules sintered together. There are micropores inside the expanded polystyrene granules, and voids between the granules. The mechanical properties of a material are determined by its apparent density: the higher it is, the greater the strength and the lower the water absorption, hygroscopicity, vapor and air permeability.

Extruded polystyrene foam

The officially recognized version is that this type of insulation was invented by specialists in the United States in the seventies. At the same time, it is known that long before that, in the Soviet Union, such material was used for the needs of economic activity. One example of application in the USSR is buoys that mark the water border. Therefore, we will give the Americans XPS primacy in the use of this material in construction. Extruded polystyrene foam is a unique material with high strength and absolute waterproofness, which makes it indispensable for insulating foundations, swimming pools and any other structures operating in a humid environment. The factors limiting the use of EPS are the flammability of this insulation and its vapor permeability.

The main types of produced polystyrene foam

• Pressless expanded polystyrene
  : EPS (Expanded Polystyrene); PSB (Suspension non-pressed expanded polystyrene foam); PSB-S (Expanded polystyrene suspension, pressless, self-extinguishing). Invented by BASF in 1951
• Extruded polystyrene foam
  : XPS (Extruded Polystyrene); Extrol, Penoplex, Styrex, Technoplex, TechnoNIKOL, URSA XPS
• Extruded polystyrene foam
  : various foreign brands; PS-1; PS-4
• Autoclave polystyrene foam
  : Styrofoam (Dow Chemical)
• Autoclave-extruded polystyrene foam
  [8]

Basic types

• Pressless - the most common type, inexpensive, more fragile. Possesses high water absorption... Consists of many granules of heterogeneous structure. The polystyrene granules are dried, foamed, dried again and heated. This composition is used to fill a mold that becomes dense as it cools.
• Press - durable and dense insulation, more expensive. It has a low heat transfer coefficient due to hermetically sealed granules. Provides for subsequent gas pressing of the foamed mixture.
• Extruded - has a homogeneous consistency of small and almost completely closed cells. Produced in accordance with GOST by extrusion - when polystyrene balls melt and a homogeneous composition is obtained, which is poured into a mold for cooling. This method allows you to make the material resistant to water penetration, dense, resistant to mechanical stress, thereby increasing the service life.

With the addition of fire retardants, extruded polystyrene foam can be made fire resistant.

• Extrusion obtained by processing the final weight of the polymer. An extruder is used in the manufacture, therefore the last 2 types are called the same material.

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There is an autoclave and autoclave-extrusion polystyrene foam, where the foaming and drying of the material is carried out using an autoclave. It is produced abroad, it is used very rarely due to its high cost.

Application

Expanded polystyrene is most often used as a heat-insulating and structural material. Scopes of its application: construction, carriage and shipbuilding, aircraft construction. Quite a large amount of expanded polystyrene is used as a packaging and electrical insulating material.

• In the military industry - as a heater; in the systems of individual protection of military personnel; like a shock absorber in helmets.
• In the production of household refrigerators as a heat insulator (in the USSR, these are serially produced refrigerators "Yarna-3", "Yarna-4", "Vizma", "Smolensk" and "Aragats-71") until the early 1960s, when expanded polystyrene was displaced by polyurethane foam.
• In the production of containers and disposable isothermal packaging for frozen products [9] [10] [11] [12]
• In the construction of buildings - the use of expanded polystyrene in Russia in the construction industry is regulated by state standards [13] [14] [15] and is limited to the use of a building envelope as a middle layer. Expanded polystyrene is widely used for insulating facades (flammability class G1). The potentially high fire hazard of this material requires mandatory preliminary full-scale tests [16]. In August 2014, the FGBU VNIIPO EMERCOM of Russia noted [17] that the use of SFTK ("Systems of facade heat-insulating composite") as a heater (thermal insulation) of the main plane of the facade of tiled polystyrene foam (only those brands that are indicated in the TS), which is not material for finishing or facing the outer surfaces of the outer walls of buildings and structures, contrary to the requirements of Article 87, part 11 of the Federal Law No. 123-FZ [18] and paragraph 5.2.3 of SP 2.13130.2012. In July 2020, the modern GOST 15588-2014 “Foamed polystyrene heat-insulating plates. Technical conditions ", indicating the mandatory presence of fire retardant additives in the material, ensuring fire safety (self-extinguishing, inability to maintain independent combustion) of expanded polystyrene plates during storage and installation.
• Since the 1970s. expanded polystyrene is used in the construction of roads, the construction of artificial reliefs and embankments, the laying of transport routes in areas with weak soils, when protecting roads from freezing, to reduce the vertical load on the structure, and in a number of other cases. Expanded polystyrene is most actively used in road construction in the USA, Japan, Finland and Norway [19]. The requirements and standards of GOST for this product in these countries are radically different from the Russian and CIS countries.
• Serves as a material for the production of toys, designer furniture and interior items [20]. It also serves as a material for creating objects of modern decorative and applied art and conceptual art [21].

Extruded polystyrene foam: instructions for use

Polyfoam of the PSB-S grade, due to its higher vapor permeability, compared to PPE, can be used for thermal insulation from the inside of the premises. Extruded polystyrene is usually used for external insulation or as a middle layer in sandwich panels. For wall insulation from the outside, plates with a thickness of 80-100 mm are used. Sheets with a thickness of 30-40 mm are often used, laid in two layers.

How to properly insulate the wall with expanded polystyrene:

• Dismantling work. Before attaching the extruded polystyrene foam or foam to the wall, dismantle the details of the drainage system, decorative elements, clean and prime the surface of the wall.
• Sticking sheets on the wall. How to properly glue polystyrene foam on the wall: the adhesive mixture is applied to the wall structure and the entire area of ​​the insulation sheet. It is especially abundantly applied to the edges and center of the sheet. The sheet is glued to the wall. The panel is fixed with dowels, which must enter the wall material by at least 50 mm. The dowels are placed in the center of the panel and at the joints.
• Sealing cracks. If the gaps are less than 20 mm, then they are blown out with polyurethane foam, if more, then they are sealed with pieces of insulation, and then foamed. The excess foam is cut off, the caps of the umbrella nails are rubbed with putty.

When insulating the facade with extruded polystyrene, waterproofing is not required. The basement walls and the foundation with a high location of groundwater require waterproofing measures.

Properties of expanded polystyrene

Water absorption

Colony of bacteria on EPS
Expanded polystyrene is capable of absorbing water in direct contact [22].The penetration of water directly into the plastic is less than 0.25 mm per year [23], therefore, the water absorption of polystyrene foam depends on its structural features, density, manufacturing technology and the duration of the period of water saturation. The water absorption of extruded polystyrene foam even after 10 days in water does not exceed 0.4% (by volume), which makes it widely used as a heater for underground and buried structures (roads, foundations) [24].

Vapor permeability

Expanded polystyrene is a low vapor permeable material [25] [26].

A feature of the vapor permeability of expanded polystyrene is that it does not depend on its degree of foaming and the density of expanded polystyrene and is always equal to 0.05 mg / (m * h * Pa) [source unspecified 1930 days

], which is not equivalent to the vapor permeability of a wooden frame made of pine, spruce or oak or mineral wool (0.55 mg / (m * h * Pa)).

Biological resistance

Despite the fact that expanded polystyrene is not susceptible to the action of fungi, microorganisms and mosses, in some cases they are able to form their colonies on its surface [27] [28] [29] [30].

Insects can settle in expanded polystyrene, equip nests of birds and rodents. The problem of damage to polystyrene foam structures by rodents has been the subject of numerous studies. Based on the results of the foam polystyrene tests performed on gray rats, house mice and vole mice, the following was established:

1. Expanded polystyrene, as a material consisting of hydrocarbons, does not contain nutrients and is not a breeding ground for rodents (and other living organisms).
2. Under compulsory conditions, rodents act on extrusion and granular polystyrene foam as well as on any other material, in cases where it is an obstacle (obstacle) to access to food and water or to meet other physiological needs of the animal.
3. Under conditions of free choice, rodents affect the expanded polystyrene to a lesser extent than under conditions of compulsion, and only if they need bedding material or there is a need to grind the incisors.
4. If there is a choice of nesting material (burlap, paper), expanded polystyrene attracts rodents in the last turn.

The results of experiments with rats and mice also showed dependence on the modification of expanded polystyrene, in particular, extruded expanded polystyrene is damaged by rodents to a lesser extent.

Durability

One of the ways to determine the durability of polystyrene foam is by alternating heating to +40 ° C, cooling to −40 ° C and holding in water. Each such cycle is assumed to be equal to 1 conditional year of operation. It is argued that the durability of products from expanded polystyrene according to this test method is at least 60 years [31], 80 years [32].

Resistant to solvents

Expanded polystyrene is not very resistant to solvents. It dissolves easily in the original styrene, aromatic hydrocarbons (benzene, toluene, xylene), chlorinated hydrocarbons (1,2-dichloroethane, carbon tetrachloride), esters, acetone, and carbon disulfide. At the same time, it is insoluble in alcohols, aliphatic hydrocarbons and ethers.

Characteristics and properties of insulation

Thermal conductivity

Expanded polystyrene board 10 cm thick and a brick wall more than 1 m have equal heat-conducting properties.
The air inside the bubbles is hermetically sealed, so the material perfectly retains heat.

The thermal conductivity coefficient varies in the range of 0.028 - 0.034 W / mK, which is much lower than the coefficient of brick or concrete.

Vapor permeability and moisture absorption

The vapor permeability index of expanded polystyrene foam is from 0.019 to 0.015 kg per meter-hour-Pascal, in contrast to an extruded product with a zero index.

The required thickness and shape is given using cutting the foam into slabs of the desired size... Steam flows through the granules into the cells.

note

Extruded polystyrene foam is not cut, because finished slabs come out of the conveyor of a certain thickness and are already smooth. As a result, steam cannot penetrate the material.

When a non-pressed product is immersed in water, up to 4% of the liquid is absorbed. Dense extruded polystyrene foam will remain almost dry and will absorb only 0.4%.

It is worth noting that the insulation will not be damaged in contact with liquids.

Strength

The material is durable, can withstand temperature from -40 to + 40 ° C up to 60 cycles (climatic years). The static bending strength of extruded material is superior to that of foamed material.

Sound absorption

A 3 cm layer of insulating material will reduce the noise penetration level by 25 decibels, which provides good sound insulation. Relevant for apartment residents.

But it will not completely relieve the noise, but only muffle it, in the presence of a thick layer of insulation. Airborne noise will not master.

Biological resistance

Polystyrene foam is not sensitive to the formation of biological activity and therefore will not become a breeding ground for mold and fungi.
This is a scientifically proven fact.

However, it can be damaged by rodents and insects. They make their way through the material in search of warmth and food.

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Destruction of expanded polystyrene

High temperature destruction

The high-temperature phase of destruction of expanded polystyrene has been well and thoroughly studied. It starts at a temperature of +160 ° C. With an increase in temperature to +200 ° C, the phase of thermal oxidative destruction begins. Above +260 ° C, the processes of thermal destruction and depolymerization prevail. Due to the fact that the heat of polymerization of polystyrene and poly - "" α "" - methylstyrene is one of the lowest among all polymers, depolymerization to the initial monomer, styrene, predominates in the processes of their destruction [33].

Modified polystyrene foam with special additives differs in the degree of high-temperature destruction according to the certification class. Modified polystyrene foam, certified according to class G1, does not degrade by more than 65% when exposed to high temperatures. The classes of modified polystyrene foam are given in the table in the section on fire resistance.

Low temperature destruction

Foamed polystyrene, like some other hydrocarbons, is capable of self-oxidation in air to form peroxides. The reaction is accompanied by depolymerization. The reaction rate is determined by the diffusion of oxygen molecules. Due to the significantly developed surface of expanded polystyrene, it oxidizes faster than polystyrene in a block [34]. For polystyrene in the form of dense products, the temperature factor is the regulating beginning of destruction. At lower temperatures, its destruction is theoretically possible in accordance with the laws of thermodynamics of polymerization processes, but due to the extremely low gas permeability of polystyrene, the partial pressure of the monomer can only change on the outer surface of the product. Accordingly, below Tpred = 310 ° C, the depolymerization of polystyrene occurs only from the surface of the product, and it can be neglected for practical purposes.

Doctor of Chemistry, Professor of the Department of Plastics Processing at the Russian Chemical Technology University named after V.I. Mendeleeva L.M. Kerber on the separation of styrene from modern expanded polystyrene:

“Under normal operating conditions, styrene will never oxidize. It oxidizes at much higher temperatures. The depolymerization of styrene can indeed proceed at temperatures above 320 degrees, but it is impossible to seriously talk about the release of styrene during the operation of expanded polystyrene blocks in the temperature range from minus 40 to plus 7 ° C.In the scientific literature there is evidence that the oxidation of styrene at temperatures up to +11 ° C practically does not occur. "

Experts also claim that a drop in the impact toughness of the material at 65 ° C was not observed over an interval of 5000 hours, and a drop in the impact strength at 20 ° C was not observed over 10 years.

The toxic nature of styrene and the ability of expanded polystyrene to release styrene is considered by European experts to be unproven. Experts, both in the construction and chemical industries, either deny the very possibility of oxidation of expanded polystyrene under normal conditions, or point to the absence of precedents, or refer to their lack of information on this issue.

In addition, the very danger of styrene is initially often exaggerated. According to large-scale scientific studies carried out in 2010 in connection with the passage of the mandatory procedure for re-registration of chemicals in the European Chemicals Agency in accordance with the REACH regulation, the following conclusions were made:

• mutagenicity - no basis for classification;
• carcinogenicity - no basis for classification;
• reproductive toxicity - no basis for classification.

What's more, keep in mind that styrene is naturally found in coffee, cinnamon, strawberries, and cheeses.

Thus, the main concerns associated with the particular toxicity of styrene, allegedly released when using expanded polystyrene, are not confirmed [33].

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Expanded polystyrene is a rather interesting material. The production method was patented back in 1928, and has been modernized many times since then. The main advantage is low thermal conductivity, and only then in light weight. Expanded polystyrene is widely used in various industries and construction, and each person, in one way or another, came across products from it in everyday life. In addition, expanded polystyrene, the price of products from which is at a low level, will be a good option if you want to insulate your home.

Table of contents

1. What is expanded polystyrene and how is it different from polystyrene?
2. Expanded polystyrene, characteristics and properties
3. Application area
4. Disadvantages of expanded polystyrene: an overview of the myths

What is expanded polystyrene and how is it different from polystyrene?

Expanded polystyrene is produced by adding gas to the polystyrene polymer mass, which, upon subsequent heating, significantly increases in volume, filling the entire mold. Depending on the type of material, a different gas is used to create volume: for simple variations, natural gas, fire-resistant types of expanded polystyrene are filled with carbon dioxide.

Quite often, amateurs tend to call polystyrene foam and polystyrene the same material. However, this is not entirely true. They have a common basis, but the differences and characteristics are quite significant. If you do not go into long spatial reasoning, then the main distinguishing features are as follows:

• the density of the foam is significantly lower, 10 kg per m3, while the indicators of polystyrene foam are 40 kg per m3,
• expanded polystyrene does not absorb steam and moisture,
• the appearance is different. Polyfoam - has internal granules, polystyrene foam is more homogeneous,
• foam plastic is characterized by a lower cost, which is noticeable when it is used as a heat-insulating material for the outer cladding of the walls of a building,
• expanded polystyrene has the best mechanical strength.

Polyfoam is produced from polymer raw materials, which are treated with water vapor, as a result of which the volume of the granules increases significantly. But at the same time, this leads to the fact that the micropores also increase in size, as a result of which the bond between the granules deteriorates and gradually, under the influence of atmospheric precipitation and climatic conditions, this leads to the fact that the material weakens. Roughly speaking, if you break a sheet of polystyrene in half, a large number of granules are formed.This is not typical of expanded polystyrene, since initially it consists of closed cells, which ensure the moisture and vapor impermeability of the material. At the beginning of production, its granules under the influence of high temperatures melt, forming a uniform fluid mass, which is filled with gas.

The material itself also has several varieties:

• Extruded polystyrene foam is practically the same material as non-pressed, the difference is in the use of equipment such as an extruder, therefore, extruded and extruded polystyrene foam is often called the same material.
• Extrusion is also obtained by processing the final mass of polymer material, and is also a homogeneous mass. The variety is used for the manufacture of disposable packaging and tableware. Roughly speaking, meat products in supermarkets are packed in packaging made of extruded polystyrene foam.

• The press method of obtaining the material is more expensive, since it involves the subsequent pressing of the gas-foamed mixture. In this case, it acquires additional strength.
• Autoclave polystyrene foam is rarely mentioned, and in fact, it is an extrusion type in which the foaming and baking of the material is performed using an autoclave.
• Pressless is one of the most popular varieties. Moisture is first removed from the polystyrene granules by drying, then foamed at a temperature of 80 ° C, after which they are again dried and then heated again. The resulting mixture is filled into a mold, where it is already self-compacting at the time of cooling. This type of expanded polystyrene is more fragile, but requires half as much isopetane for its production, which affects the final cost.

Expanded polystyrene, characteristics and properties

Expanded polystyrene is an ambiguous material: someone exalts its properties to the skies, someone, on the contrary, foaming at the mouth, demands an immediate and complete ban on its use on the basis of "exposing the works of one academician." True, the ubiquity of expanded polystyrene and its high popularity incline conclusions towards the fact that this material is really good and has the following advantages:

• Low thermal conductivity allows a significant insulation effect to be achieved. In fact, 11 cm of expanded polystyrene can provide the same thermal insulation as a silicate brick wall more than two meters thick. The thermal conductivity of the material is 0.027 W / mK, which is significantly lower than that of concrete or brick,
• Moisture resistance of the material. Even with prolonged exposure to moisture, the absorbency will be no more than 6%, so there is no need to fear deformation of the structure of expanded polystyrene.
• Expanded polystyrene is durable and can withstand up to 60 cycles of exposure to temperatures from -40 to + 40 ° C. Each cycle constitutes an estimated climatic year.
• Insensitivity to the formation of biological media. Expanded polystyrene will not become a breeding ground for fungi and mold.

• Harmlessness of the material. In its production, non-toxic components are used, therefore, products from expanded polystyrene are also used in the food industry. For example, for storing food.
• Due to its light weight, insulation of building facades with expanded polystyrene takes much less time and effort than using other means.
• Fire-resistant grades of material, when exposed to an open flame, tend to self-extinguish and melt, not spreading combustion. The spontaneous combustion temperature of expanded polystyrene is + 490 ° C, which is almost two times higher than that of wood. If the material is not exposed to an open source of flame for more than four seconds, the expanded polystyrene extinguishes. The heat energy during combustion of the material is 7 times less than that of a tree. Therefore, expanded polystyrene is not able to support the fire site.
• Providing soundproofing. This quality is especially important for residents of standard apartments. A 3 cm layer of insulating material is sufficient to reduce noise penetration by 25 dB.
• The vapor permeability of the material is at a low level of 0.05 Mg / m * h * Pa, regardless of the degree of foaming and the density of the grade. In fact, the vapor permeability indicators are similar to the timber frame of pine or oak.
• Resistant to alcohols and ethers, but easily subject to destruction when solvents come into contact with the surface of the material.
• The tensile strength is at least 20 MPa.

As can be seen from the above, expanded polystyrene is an effective tool for solving many problems: from using some of its varieties as packaging to providing heat and waterproofing of building facades. In addition, the material is used for other purposes in construction, which will be discussed below.

Application area

Expanded polystyrene in construction is used primarily for insulating the following elements:

• water pipes,
• roofs,
• floors,
• door and window slopes,
• walls.

For example, the consumption of expanded polystyrene for pipe insulation is economically justified and reasonable due to its capabilities. Moreover, for these purposes, molded block polystyrene foam is used, which allows, in the event of a pipe damage, to easily access it by removing the desired section of the protective coating.

Expanded polystyrene is actively used in the construction of transport routes. It reduces the effect of vertical loading on the floor during construction of buildings. Widespread in the production of SIP panels.

The scope of application of expanded polystyrene, the characteristics of which, combined with a low price, make it extremely attractive for use in any industry, is practically unlimited. The only thing that should be taken into account is that the material has a low density, therefore, it is susceptible to any mechanical damage.

Disadvantages of expanded polystyrene: an overview of the myths

In addition to the bouquet of advantages, there are also disadvantages. Moreover, a large number of various myths are associated with expanded polystyrene, which must be considered in more detail:

• Many manufacturers claim that extruded expanded polystyrene foam is significantly superior to other varieties, as evidence of which they often expose a table of comparative characteristics of this variety in comparison with ordinary foam. Nevertheless, the difference in thermal conductivity between extruded and extruded polystyrene foam is practically not noticeable and amounts to 0.002 units, at the same time, due to advertising, the cost of extrusion plates for insulation is higher.
• The maximum density of expanded polystyrene gives the same high performance when insulated. According to experts, such a statement has some discrepancies with reality, since the more closely the molecules adhere to each other, the higher the thermal conductivity becomes and it is easier for cold to penetrate the room. A way out of this situation will be the use of low-density expanded polystyrene plates, which must be covered with a reinforcing mesh and a protective layer of primer in order to increase their mechanical strength.

• Fire-resistant polystyrene foam is absolutely non-flammable and harmless to the human body. Any building material, when exposed to an open flame, will exhibit combustion properties, more or less. However, the spontaneous combustion temperature of expanded polystyrene is higher than that of wood, and in addition, it emits significantly less thermal energy during combustion. It is important to remember that fire-resistant varieties, despite the loud name, are by no means able to stop the flame, only to reduce its effect. Carbon dioxide, which is used in its production, will become a serious disadvantage of a fire-resistant grade compared to the usual one.As a result, when reflowing, the material will begin to emit a significantly large amount of harmful substances. Some sellers talk about incombustibility on the basis of demonstrative experience: when the base with a plate of insulation fixed on it begins to warm up from the back side. When exposed to high temperatures, polystyrene foam begins to melt and deform, while there is no fire. However, as long as the flame is exposed to it, the material will continue to burn.
• Fire retardants added to polystyrene foam for its fire resistance are "in any case, pure poison." Another controversial statement. A fire retardant is a component containing substances in its structure that slow down the combustion process. They differ in composition and contain various components, ranging from formaldehydes, which are really dangerous for humans, to magnesium salts, which are quite environmentally friendly and safe. Recently, solutions based on inorganic salts have been increasingly used, so they are not capable of harming health. Fire retardants are often used to impregnate and apply a protective layer to wood to increase its fire resistance.
• Installation of polystyrene foam insulation materials is not able to provide heat. In fact, the task of the insulation is not to bring heat, but to keep it indoors. Roughly speaking, the use of insulating plates will significantly reduce the escape of heat outside the premises, thus, you will not have to heat the street at your own expense.
• "Expanded polystyrene is hazardous to health." Modern production allows you to create material from environmentally friendly components, so there is no threat to health. Moreover, the widespread use of products for storing semi-finished products and for use in everyday life speaks precisely of the safety of the material.

More often, problems arise when you want to buy expanded polystyrene of cheaper and lower quality varieties. Insulation plates made of such a material really have less strength and are able to begin to deform even at temperatures above 40 ° C. The main rule when using materials from expanded polystyrene in any industry will be to ensure quality and reliability, for which you have to pay. And then in the course of operation only dignity will appear.

Fire hazard of expanded polystyrene

Fire hazard of untreated polystyrene foam

Unmodified polystyrene foam (flammability class G4) is a flammable material, which can be ignited by the flame of matches, a blowtorch, or from autogenous welding sparks. Expanded polystyrene does not ignite from a calcined iron wire, a burning cigarette and sparks generated at the point of steel [35]. Expanded polystyrene refers to synthetic materials that are characterized by increased flammability. It is able to store energy from an external heat source in the surface layers, spreading fire and initiating fire intensification [36].

The flash point of expanded polystyrene ranges from 210 ° C to 440 ° C depending on the additives used by the manufacturers [37] [38]. The ignition temperature of a specific modification of polystyrene foam is determined according to the certification class.

When conventional expanded polystyrene (G4 flammability class) ignites, a temperature of 1200 ° C develops in a short time [35]; when using special additives (fire retardants), the combustion temperature can be reduced according to the combustion class (G3 flammability class). Combustion of expanded polystyrene takes place with the formation of toxic smoke of varying degrees and intensity, depending on the impurities added to the expanded polystyrene to reduce smoke generation. Smoke emission of toxic substances is 36 times greater in volume than that of wood.

Combustion of ordinary expanded polystyrene (G4 flammability class) is accompanied by the formation of toxic products: hydrogen cyanide, hydrogen bromide, etc. [39] [40].

For these reasons, products made of untreated polystyrene foam (flammability class G4) do not have approval certificates for use in construction work.

Manufacturers use expanded polystyrene modified by special additives (fire retardants), thanks to which the material has different classes of ignition, combustibility and smoke generation.

Thus, with correct installation, in accordance with GOST 15588-2014 “Foam polystyrene heat-insulating plates. Technical conditions ", expanded polystyrene does not pose a threat to the fire safety of buildings. The "wet facade" technology (WDVS, EIFS, ETICS), which implies the use of expanded polystyrene as insulation in the building envelope, is widely used in construction.

Modified polystyrene foam for fire safety

To reduce the fire hazard of expanded polystyrene, when it is received, fire retardants are added to it. The resulting material is called self-extinguishing polystyrene foam (flammability class G3) and is indicated by a number of Russian manufacturers with an additional letter "C" at the end (for example, PSB-S) [41].

On 05/01/2009, a new federal law FZ-123 "Technical regulations on fire safety requirements" came into effect. The methodology for determining the flammability group of combustible building materials has changed. Namely, in article 13, paragraph 6, a requirement appeared that excludes the formation of melt drops in materials with a group G1-G2 [42]

Considering that the melting point of polystyrene is about 220 ° C, then all heaters based on this polymer (including extruded polystyrene foam) from 01.05.2009 will be classified with a flammability group not higher than G3.

Before the entry into force of Federal Law 123, the flammability group of brands with the addition of flame retardants was characterized as G1.

A decrease in the combustibility of expanded polystyrene in most cases is achieved by replacing the combustible gas for "inflating" the granules with carbon dioxide [43].

Types of expanded polystyrene

The proliferation of PPP was a response to a request for insulation that can effectively retain heat in buildings constructed from traditional building materials. In big cities, huge amounts of money are spent on heating buildings in winter. And emissions from thermal power plants lead to a significant deterioration of the environmental situation.

Among many areas, one of the most successful has been the use of expanded polystyrene obtained by foaming polystyrene when processed in the presence of high temperatures.

The final material is in the form of granules, the diameter of which varies from 2 to 8 mm, which are sintered together when exposed to steam shock.

As a result, a material was learned that only mineral wool can compare with in terms of thermal insulation properties. It is interesting to compare PPP with other materials.

A sheet of material 10 cm thick can replace:

• 400 cm of heavy concrete;
• 150 cm of building bricks;
• 100 cm of expanded clay concrete;
• 60 cm of aerated concrete;
• 40 cm pine wood.

Also, due to the presence of closed pores in the structure of the material, it perfectly reflects sound, therefore it is often used as sound insulation.

Depending on the production technology, expanded polystyrene is divided:

• on pressless expanded polystyrene (PSB);
• pressed expanded polystyrene (PS);
• extruded polystyrene foam (EPS).

These types have some differences not only in technology, but also in characteristics. Therefore, their areas of application also differ.

Notes

1. Kabanov V.A. and others.
   vol. 2 L - Polynose fibers // Encyclopedia of Polymers. - M .: Soviet Encyclopedia, 1974 .-- 1032 p. - 35,000 copies.
2. French Patent No. 668142 (Chem. Abs. 24, 1477, 1930).
3. German Patent No. 644102 (Chem. Abs, 31, 5483, 1937)
4. Berlin A. An. Basics of the production of gas-filled plastics and elastomers. - M .: Goskhimizdat, 1956.
5. Chukhlanov V. Yu., Panov Yu. T., Sinyavin A. V., Ermolaeva E. V. Gas-filled plastics. Tutorial. - Vladimir: Vladimir State University Publishing House, 2007.
6. Kerzhkovskaya EM Properties and application of PS-B foam.- L: LDNTP, 1960.
7. Andrianov R.A.New grades of expanded polystyrene. Building materials industry in Moscow. - Issue No. 11. - M .: Glavmospromstroimaterialy, 1962.
8. Federal Republic of Germany patent No. 92606 dated 04/07/1955.
9. Discussion and Possible Action Regarding a Ban of the Use of Expanded Polystyrene (EPS) Food Containers (Study Issue) // December 18, 2012.
10. POLICY TOOLS FOR REDUCING IMPACT OF SINGLE-USE, CARRYOUT PLASTIC BAGS AND EPS FOOD PACKAGING // Final Report June 2, 2008
11. Nguyen L. An Assessment of Policies on Polystyrene Food Ware Bans.// San Jose State University 10.01 / 2012
12. S8619 Prohibits food establishments from using expanded polystyrene foam disposable food service containers beginning 1/1/15.
13. GOST 15588-2014 “Foam polystyrene heat-insulating plates. Technical conditions ". Entered into force on 01.07.2015
14. GOST R 53786-2010 “Composite thermal insulation facade systems with external plaster layers. Terms and Definitions"
15. GOST R 53785-2010 “Composite thermal insulation facade systems with external plaster layers. Classification"
16. LETTER of the State Construction Committee of the Russian Federation N 9-18 / 294, GUGPS of the Ministry of Internal Affairs of the Russian Federation N 20 / 2.2 / 1756 dated 06/18/1999 "ON INSULATION OF THE EXTERNAL WALLS OF BUILDINGS"
17. Letter from FGBU VNIIPO EMERCOM of Russia dated 07.08.2014 No. 3550-13-2-02
18. FEDERAL LAW TECHNICAL REGULATIONS ON FIRE SAFETY REQUIREMENTS dated 22.07.2008 No. 123-FZ
19. Bjorvika
20. Styrofoam designer furniture - constructive and affordable
21. Styrofoam robots
22. Pavlov V.A. Expanded polystyrene. - M .: "Chemistry", 1973.
23. Khrenov A.E. Migration of harmful impurities from polymeric materials during the construction of underground structures and the laying of communications. - No. 7. - 2005.
24. Egorova EI, Koptenarmusov VB Fundamentals of polystyrene plastics technology. - St. Petersburg: Himizdat, 2005.
25. Table of density, thermal conductivity and vapor permeability of various materials
26. Table of density, thermal conductivity and vapor permeability of various materials: Repair and furnishing of an apartment, building a house - my answers to questions
27. Semenov SA Destruction and protection of polymeric materials during operation under the influence of microorganisms // Dissertation for the degree of Doctor of Technical Sciences, Russian Academy of Sciences Institute of Chemical Physics. N.N.Semenova. - M., 2001.
28. Atiq N. Biodegradability of Synthetic Plastics Polystyrene and Styrofoam by Fungal Isolates // Department of Microbiology Quaid-i-Azam University, Islamabad, 2011.
29. Naima Atiq T., Ahmed S., Ali M., Andleeb S., Ahmad B., Geoffery R. Isolation and identification of polystyrene biodegrading bacteria from soil.//African Journal of Microbiology Research Vol. 4 (14), pp. 1537-1541, 18 July, 2010.
30. Richardson N. Beurteilung von mikrobiell befallenen Materialien aus der Trittschalldämmung // AGÖF Kongress Reader September 2010.
31. Hed G. Service Life Estimations of Building Components. Munich: Hanser. Report TR28: 1999. Gävle, Sweden: Royal Institute of Technology, Center for Built Environment, Stockholm, 1999. - P. 46.
32. Test report No. 225 dated 25.12.2001. NIISF RAASN. Testing laboratory for thermophysical and acoustic measurements)
33. ↑ 12
    Expanded polystyrene - Properties. 4108.ru. Retrieved April 10, 2016.
34. Emmanuel NM, Buchachenko AL Chemical physics of aging and stabilization of polymers. - M .: Nauka, 1982.
35. ↑ 12
    OCT 301-05-202-92E “Expandable polystyrene. Technical conditions. Industry standard "
36. Guyumdzhyan P.P., Kokanin S.V., Piskunov A.A.On fire hazard of polystyrene foam for construction purposes // Pozharovzryvoopasnost. - T. 20, No. 8. - 2011.
37. Minutes No. 255 dated 28.08.2007 for the identification control of expanded polystyrene material PSB-S 25 FGU VNIIPO EMERCOM of Russia
38. Kodolov V.I.Flammability and fire resistance of polymeric materials. M., Chemistry, 1976.
39. Toxicity of combustion products of synthetic polymers. Survey information. Series: Polymerized plastics. - NIITEKHIM, 1978.
40. Toxicity of volatile products from thermal exposure to plastics during processing. Series: Polymerized plastics. - NIITEKHIM, 1978.
41. Evtumyan A.S., Molchadovsky OI Fire hazard of heat-insulating materials from expanded polystyrene. Fire safety. - 2006. - No. 6.
42. Federal Law of 22.07.2008 N 123-FZ (as amended on 03.07.2016) "Technical regulations on fire safety requirements" (Russian) // Wikipedia. - 2017-03-12.
43. Basic Fire Safety Requirements - Thermal Insulation Systems