Rus Articles Journal

For what thermal insulation is necessary?

expanded polystyrene

Heat insulators on an organic basis the Heat-insulating materials on an organic basis became popular

when warming facades lung by method thanks to the low cost.

polystyrene foam plates and blocks, products from made foam karbamidno - formaldehyde pitch, the made foam penopolietilen sewed and which is not sewed, a penopolipropilen, rigid polyurethane foam belong to these materials.

The made foam polystyrene is most popular, it is polyfoam.

Today for thermal insulation use more than 60% of all expanded polystyrene made in Europe.

Such characteristic features are inherent in the made foam polystyrene :

For bulk of consumers an important factor is that expanded polystyrene is cheaper than the majority of other heaters, but there are many factors much stronger influencing its right choice as heat-insulating material for facades;

It is strong on compression, is capable to maintain rather high mechanical loading at the minimum density and at the same time is well processed, is konstruktsionno flexible, is easily mounted;

Differs in low density thanks to what practically does not change load of the bearing designs and the base;

Expanded polystyrene differs in high ecological rates, it is not toxic, does not allocate harmful chemical compounds, cancerogenic dust and fibers, is simple and convenient in work, does not demand use of overalls and means of individual protection;

It is steady against effect of solutions of acids and alkalis, alcohols, is inert in relation to inorganic construction materials (concrete, bitumen, clay, lime, sand, cement), it is not affected by sea water, soap, solutions of the moistening and bleaching substances, kremniyorganichesky oils;

(However it we will dissolve in organic solvents, it is not steady against influence of pitches, bituminous solutions, gasoline and diesel fuel, strong oxidizers and reducers.

Under the influence of acetone and Whyte - a spiritist, gasoline, kerosene expanded polystyrene is dissolved in a few minutes. In vapors of these solvents expanded polystyrene can hold on several days, but then inevitably collapses.

And even if works with use of organic solvents (for example, when coloring by oil or alkidny paint) will make indoors, and expanded polystyrene is outside, getting through walls there will be enough vapors to cause its destruction.)

Organic thermal insulation on the basis of expanded polystyrene has is insignificant small vapor permeability that needs to be considered, projecting warming of a facade expanded polystyrene. A bad conclusion of steam from premises causes discomfort;

Expanded polystyrene well absorbs water, besides, water in expanded polystyrene appears in the course of its production. This circumstance in combination with low vapor permeability leads to the fact that expanded polystyrene there can be about 6% of water. In a cold season water freezes, and the formed ice breaks off walls of cells of expanded polystyrene that, naturally, affects its heat-insulating properties;

Expanded polystyrene possesses very low heat conductivity. The polyfoam 10 mm thick layer on heat conductivity is approximately equivalent to a layer of mineral wool 20 mm thick, a tree 40 mm thick, a bricklaying 190 mm thick or 400 mm of concrete;

Unfortunately, this indicator has property to worsen over time. Polystyrene is made foam gas mix on the basis of a pentane or various freon. 1 m 3 expanded polystyrene contains from 3 to 6 billion closed cells filled with these gases. Heat conductivity of gases is several times lower than heat conductivity of air. In use leads gradual volatilization of the gases filling a time of material and replacement with their air to decrease in the heat-insulating properties of expanded polystyrene. In process of replacement of gases with air heat conductivity of expanded polystyrene can increase by 25%.

Organic polymers, and in it polystyrene is not an exception, quite easily collapse under the influence of high temperatures. Expanded polystyrene is efficient in the range of temperatures from - 180 to +80 C. Within several minutes it can sustain heating to 95 C and is very short-term to 110 C. In the summer under the influence of sunlight temperature of a wall can reach 125 C (depending on color of a wall). You see that heat insulation on the basis of expanded polystyrene can be destroyed for only one hot summer season that in connection with the future global warming gains the dominating value;

(Besides, polystyrene can collapse not only under the influence of heat, but also ultra-violet radiation. It by all means needs to be considered and to surely protect penopolistirolovy isolation from the sun.

We will wound expanded polystyrene and from the point of view of fire safety. In an open flame expanded polystyrene lights up and burns with formation of the burning falling drops. Fortunately, burning of drops out of a flame lasts only 1 - 4 seconds. The expanded polystyrene modified by fire-retarding agents (ognegasyashchy additives) at first melts, and then passes into a gaseous state, without sustaining combustion.)

producers declare In the advertizing purposes that expanded polystyrene differs in durability and 10 - 20, and even 50 years can serve. However, as we see, this term is removed for ideal conditions of operation, and in real life it can be much lower.

Distinguish on two main types expanded polystyrene: block (PBS) and extrusive (EPPS).

Block expanded polystyrene is made foaming of polystyrene in a press - a form. As a result receive large blocks which cut then on plates.

Extrusive expanded polystyrene is received by extrusion (breakdown through a crack). At the same time the plate is formed at once.

As conditions of orientation of molecules in both cases different, materials differ on properties a little. So, the main indicator of heat-insulating material - heat conductivity coefficient - at block expanded polystyrene makes 0,04, and at extrusive - 0,028 - 0,03 In / m*k.

At block expanded polystyrene the water absorption coefficient in 24 hours averages 0,5 - 2% of moisture, and at extrusive - 0,1 - 0,2%. In other words, block polyfoam absorbs moisture in 5 - 10 times more, than extrusive. But extrusive expanded polystyrene significantly, time in three, is more expensive than block.

Depending on measures for protection of material against fire, polystyrene foam plates make two types: without fire-retarding agent (PSB) and with fire-retarding agent (PSB - C).

They are also subdivided into brands depending on extreme value of density: 15, 25, 35 and 50.

Usual sizes of plates :

on length - from 800 to 5000 mm with an interval through 50 mm;

on width - from 500 to 1300 mm with an interval through 50 mm;

on thickness - from 20 to 500 mm with an interval through 10 mm.

But it is not dogma, and by request of the consumer plates of other sizes can be made.