What determines the thermal conductivity of expanded polystyrene

By Admin | Construction Materials
23 April 2016

lists the heaters, in the first place has always put the thermal conductivity of the material.It depends on how much material is contained in the air.After all, the air environment is an excellent natural insulator.Note that the ability to conduct heat decreases with increasing sparsity environment.So it is best to keep warm layer of vacuum.This principle is based thermoses work.But with the construction of the vacuum to create a problem, however limited to normal air.For example, the low thermal conductivity of expanded polystyrene, especially extruded, due to the fact that most of the air in it more than enough.

The thermal conductivity of extruded polystyrene foam

Contents:

  1. What affects the ability of polystyrene foam to conduct heat
  2. Styrofoam and other insulation: comparison

What affects the ability of polystyrene conductHeat

to clearly understand what is the thermal conductivity, take a piece of material thickness meter and an area of ​​one square meter.A

nd one side of it is heated and the second cold reserve.The difference between these temperatures should be tenfold.By measuring the amount of heat that passes per second on the cold side, we obtain the thermal conductivity.

Why is styrofoam well able to keep both heat and cold?It turns out the whole thing in its structure.Structurally, the active material consists of a plurality of sealed polyhedral cells having a size of 2 to 8 millimeters.Inside them is the air - it is 98 percent and is a wonderful insulator.For polystyrene cell walls accounts for only 2 percent of the total weight of the material.

It should be noted that the thermal conductivity of extruded polystyrene foam remains unchanged over time.This distinguishes the material from other foams whose cells are filled not with air, but other gas.After the gas has the ability to dissipate gradually, and the air and remains sealed inside the polystyrene cells.

Buying foam, we usually ask the seller about what the density of the material.After all, we've learned that the density and the ability to conduct heat is inextricably linked to each other.There are even tables of this dependence, that can help you choose the right brand of insulation.

density polystyrene foam kg / m3 Thermal Conductivity Watts. / UV
10 0,044
15 0,038
20 0,035
25 0,034
30 0,033
35 0,032

However, at the present time have come up with an improved insulation, which introduced graphite additives.Thanks to them, the thermal conductivity of polystyrene foam of varying density remains unchanged.Its value - from 0.03 to 0.033 watts per meter per Kelvin.So now, getting a modern improved Epps, there is no need to check the density.

marking polystyrene thermal conductivity does not depend on the density:

Make Styrofoam Thermal Conductivity Watts. / UV
EPS 50 0.031 - 0.032
EPS70 0.033 - 0.032
EPS 80 0.031
EPS 100 0.030 - 0.033
EPS 120 0.031
EPS 150 0.030 - 0.031
EPS 200 0.031

Styrofoam and other insulation: comparison

compare the thermal conductivity of mineral wool and polystyrene.At last the figure lower at - from 0,028 to 0,034 watts per meter per Kelvin.Thermal performance Epps without graphite additives decrease with increasing density.Thus, for example, extruded polystyrene, whose thermal conductivity of 0.03 watt per meter per Kelvin, has a density of 45 kilograms per cubic meter.

Comparing these figures from a variety of heaters, it can be concluded in favor of the Epps.Two-centimetric layer of the material keeps the heat as well as mineral wool layer of 3.8 centimeters, the usual foam layer 3 centimeter wooden board thickness of 20 centimeters.It is necessary to lay a brick wall 37 centimeters thick and foam concrete - 27 centimeters.Impressive, is not it?

Additions
  • Comments and opinions on the use of extruded polystyrene

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