{"id":1271,"date":"2016-05-04T19:32:30","date_gmt":"2016-05-04T19:32:30","guid":{"rendered":"http:\/\/polymers.com.ua\/?p=1271"},"modified":"2016-05-04T19:32:30","modified_gmt":"2016-05-04T19:32:30","slug":"classification-of-fire-resistance-of-polymers","status":"publish","type":"post","link":"https:\/\/polymers.com.ua\/en\/classification-of-fire-resistance-of-polymers\/","title":{"rendered":"Classification of fire resistance of polymers"},"content":{"rendered":"

\"\"<\/a>Fire resistance of polymers and polymeric materials (fire-resistance, Feuerbestandigkeit, resistance au feu) – is the ability of polymers to resist the action of fire.<\/p>\n

Describing the polymers of the flame retardancy, often talk about their combustibility (flammability).<\/p>\n

Classification of fire resistance of polymers<\/strong><\/em>
\nIn the USSR, for fire resistance (flammability), the materials were usually divided into:<\/p>\n

combustible,
\nnonflammable,
\nnon-flammable;
\nabroad polymers are divided into:<\/p>\n

combustible,
\nflame-retardant,
\nnonflammable,
\nself-extinguishing,
\nincombustible.
\nThis classification is arbitrary as not only the fire depends on the type of material, but also on the ignition conditions, the nature of the flame.<\/p>\n

Test methods for fire resistance of polymeric materials<\/em><\/p>\n

fire resistance testing methods of polymers are so varied that a comparative assessment of the polymers of this indicator on the basis of data from different countries very difficult. Furthermore, experimental error is usually quite high. Quite often the same polymers on the basis of test results according to one of the methods referred to as non-combustible, differently – even to the self-extinguishing flammable.<\/p>\n

In the USSR, it was used several methods to evaluate the fire resistance of polymers. According to one of them (calorimetric) determine the flammability index. In another method of fire is characterized by oxygen index flammability.<\/p>\n

There are a number of approximate methods for evaluating the fire resistance of polymers. At the same time on polymer flammability accessories (ie ability under the influence of fire and high temperatures to burn with heat release) to a particular type are judged on the following parameters:<\/p>\n

1) The time of self-burning (smoldering) of the sample and the loss of its mass;<\/p>\n

2) flame propagation velocity.<\/p>\n

The first performance is determined by one of the common methods of rapid, so-called method of “fire-tube” (polymer sample is placed in the pipe vertically). Polymers considered flammable if weight loss when tested by this method more than 20% and the duration of self-combustion is 60 seconds.<\/p>\n

Flame spread rate determined by the length of burnt (for 2 min) of the sample that is disposed horizontally and ignited at one end. From the group of combustible materials tested by this method, emit flammable materials in which combustion propagates over the entire sample length, i.e. 300 mm.<\/p>\n

Abroad, fire resistance of polymers, as well as in the USSR, the sample is evaluated by the combustion speed, and the time of its independent burning after several consecutive ignition. When determining the fire resistance of polymers, some methods use large samples; so, ASTM E84-61 method is used to determine the fire resistance of building materials and structures.<\/p>\n

For a complete description of flammability of polymeric material is determined by:<\/p>\n

ignition temperature;
\nThe temperature of the corruption;
\nAuto-ignition temperature;
\nThe temperature Self-heating;
\nThe ability to smoke emission;
\nThe ability to form hot melt;
\nToxicity of breakdown products.
\nFactors that affect the fire resistance of polymeric materials<\/p>\n

When burning polymer flows a series of chemical and physical processes. For convenience, consider three areas of polymers burning:<\/p>\n

gas layer – it is mainly, thermo-oxidative degradation products of destruction of the surface of the polymer layer, and there is an intensive mass transfer and heat transfer;
\nthe surface layer of the polymer, which is subject flame action;
\ninner polymer layers adjacent to the surface layer; here flows mainly thermal degradation of the polymer. From the nature of the products formed during pyrolysis in the third zone, and the rate of diffusion of the surface depends on the further course of the ignition and combustion processes.
\nBased on the results of the study of combustion processes of different polymers, established following the laws of fire resistance of polymers:<\/p>\n

self-extinguishing material may occur due to evaporation from the surface of a large number of non-combustible particles, or formation on the surface of the protective polymer films that do not support combustion;
\nintroduction of phosphorus into the polymer increases the proportion of endothermic processes ( “cooling” of the material) and the formation in some cases lasting coke (faster cokes polymer, the higher its fire resistance), the introduction halogens lowers the flame temperature of the gas layer at the surface of the resin and the inhibition of ignition;
\nFire halogen-containing polymers depending upon the nature of the halogen is reduced in the order: Br> C1> F;
\nco-polymeric material in the presence of phosphorus and a halogen atom (especially bromine), halogen and antimony has a synergistic effect (i.e. the effect is greater than the sum of the effects of individual substances) to enhance flame retardancy (at a certain ratio of the respective pairs);
\nat the close on the chemical nature of polymers flame resistance increases with temperature resistance;
\nfire determined by the chemical structure of the polymer, for example, the introduction of aromatic units, replacing R-O- groups at C-F C, by reducing the length of the alkyl chain at the phosphorus atom increases the fire resistance of the polymer;
\nwith increased packing density in fire macromolecules of similar chemical nature of the polymers increases.
\nFor fire-resistant or non-combustible polymers include the following groups:<\/p>\n

inorganic and organometallic some;
\norganic macromolecule containing aromatic or heterocyclic groups;
\nfully fluorinated, galogenftorirovannye or fully halogenated.
\nFire-resistant polymers:<\/p>\n

Self-extinguishing in making them out of the flame (self-extinguishing)
\nor no burning (non-combustible).
\nWhen exposed to flame, some organometallic or inorganic polymers combustible gases are formed in small amounts or not formed at all. Such polymers are also characterized by high thermal stability. For example, polimetalloorganosilokeany (metal – Al or Ti), in which macromolecules contained in the side branches dialkilfosfinatnye groups can withstand temperatures up to 800 \u00b0 C. However, such polymers can become heated (flameless combustion) and in some cases as a result of spraying with the melt surface to become a source of combustion. The polymers in the structure which are condensed aromatic or heterocyclic ring, quickly coke, which provides them with a lower flammability or complete non-flammability.<\/p>\n

A special place in this series and take graphitizing carbonized polymers. Finally, the burning of some polymers is accompanied by a large endothermic effect associated with evaporation from the surface of incombustible particles such as, for example, some fluorinated or fully halogenated polymers. However, released during the combustion of the gases fluorine-containing polymers are often toxic.<\/p>\n

Ways to improve the flame retardancy of polymeric materials<\/p>\n

To impart or improve fire resistance, there are several ways:<\/p>\n

1) applying a fire-retardant coating on the surface of the product;<\/p>\n

2) introducing the fillers having reduced flammability, a polymer-based composition;<\/p>\n

3) introduction of flame retardants flame retardants – inert (not entering into a chemical reaction with the polymer) and reactive (chemical modification).<\/p>\n

The first two methods are ineffective. When burning fire retardant coating (eg based on liquid glass) can become heated and peeled off from the base material. Filler (asbestos, kaolin, cement, etc.) May in some cases serve as a kind of wick and promote fire. A more effective way to third.<\/p>\n

 <\/p>\n

Bibliography:
\nFire hazards of substances and materials, Manual, [h. 1-21, Moscow, 1966-70; H ind ers inn R. R., Wagner G., Fire retaraancy, in the book .: Encyclopedia of polymer science and technology, v. 7, N. Y.-L. [A. o], 1967.;
\nKodolovV.I., SapogovaL.A., SpasskiyS.S, Plast, weight, number 10,
\n40 A969); Nametz R. C, Ind. and Eng. Chem., 59, number 5,
\n99 A967); Einhorn I. N., J. Macromol. Sci., D 1, number 2,
\n113 A971); V on 1 g e H., Flammfestmachen von Kunststoffen,
\nHeidelberg, 1966. VI Kodolov, J. S. Nikitin.
\nAuthor: Kargin VA, academician of the USSR
\nSource: Encyclopedia of Polymer, edited by VA Kargin
\nDate in the source: 1972<\/p>","protected":false},"excerpt":{"rendered":"

Fire resistance of polymers and polymeric materials (fire-resistance, Feuerbestandigkeit, resistance au feu) – is the ability of polymers to resist the action of fire. Describing the polymers of the flame retardancy, often talk about their combustibility (flammability). Classification of fire resistance of polymers In the USSR, for fire resistance (flammability), the materials were usually divided […]<\/p>\n

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