The method of production of expanded polystyrene was patented at the end of the 20s of the last century, having undergone numerous modernizations since then. Expanded polystyrene, characterized by low thermal conductivity and light weight, has found the widest application in many areas of production, in everyday life and as a finishing building material.
How is polystyrene foam different from polystyrene?
Expanded polystyrene is a product of gas injection into a polystyrene mass. With further heating, this mass of polymer increases significantly in its volume and fills the entire mold. To create the required volume, a different gas can be used, which depends on the type of polystyrene foam produced. For simple heaters with standard properties, air is used, which is pumped in to fill cavities in the mass of polystyrene, and carbon dioxide is used to impart fire resistance to certain grades of EPS.
When creating this polymer, various additional components can also be involved in the form of flame retardants, plasticizing compounds and dyes.
The beginning of the technological process of obtaining a heat insulator begins from the moment the individual styrene granules are filled with gas with the subsequent dissolution of this mixture in the polymer mass. Then this mass is subjected to heating with the help of low boiling liquid vapor. As a result, the size of styrene granules increases, they fill the space, sintering into a single whole. As a result, it remains to cut the material obtained in this way into plates of the required size, and they can be used in construction.
Styrofoam is usually confused with polystyrene, but these are completely different materials. The fact is that expanded polystyrene is a product of extrusion, which consists in melting polystyrene granules and binding these granules at the molecular level. The essence of the process of manufacturing polystyrene is to combine polystyrene granules with each other as a result of polymer processing with dry steam.
Technological methods and form of release
It is customary to distinguish between three types of expanded polystyrene with their unique properties, which are due to the method of manufacturing a particular insulation.
The first is a polymer produced by a non-pressing method. The structure of such a material is replete with pores and granules of 5 mm - 10 mm. This type of insulation has a high level of moisture absorption. The material of the brands is on sale: C-15, C-25, and so on. The number indicated in the marking of the material indicates its density.
Expanded polystyrene, obtained by production under pressure, is a material with hermetically sealed internal pores. Due to this, such a pressed heat insulator has good thermal insulation properties, high density and mechanical strength. The brand is designated by the letters PS.
Extruded polystyrene foam is the third type of this polymer. Bearing the designation EPPS, it is structurally similar to pressed materials, but its pores have a much smaller size, not exceeding 0.2 mm. This insulation is most often used in construction. The material has different density, which is indicated on the package, for example, EPS 25, EPS 30 and so on.
There are also known foreign autoclave and autoclave-extrusion types of insulation. Due to their very expensive production, they are rarely used in domestic construction.
The dimensions of a sheet of this material, the thickness of which is about 20 mm, 50 mm, 100 mm, as well as 30 and 40 mm, are 1000x1000, 1000x1200, 2000x1000 and 2000x1200 millimeters. Based on these indicators, the consumer can choose a block of EPS sheets both for insulation of rather large surfaces, for example, as a substrate for a laminate for a warm floor, and for relatively small areas to be insulated.
Properties of expanded polystyrene
The density and other technical parameters of this material are due to the technology of its production.
Among them, in the first place is its thermal conductivity, thanks to which expanded polystyrene is such a popular insulating material. The presence of gas bubbles in its structure serves as a factor in the preservation of the indoor microclimate. The thermal conductivity coefficient of this material is 0.028 - 0.034 W / (m. K). The thermal conductivity of this insulation will be the higher, the higher its density.
Another useful property of PPS is its vapor permeability, the indicator of which for its different brands ranges between 0.019 and 0.015 mg / m • h • Pa. This parameter is higher than zero, because the sheets of insulation are cut, therefore, air can penetrate through the cuts into the thickness of the material.
The moisture permeability of expanded polystyrene is practically zero, that is, it does not allow moisture to pass through. When a PBS fragment is immersed in water, it absorbs no more than 0.4% moisture, unlike PBS, which can absorb up to 4% of water. Therefore, the material is resistant to humid environments.
The strength of this material, equal to 0.4 - 1 kg / cm2, is due to the strength of bonds between individual polymer granules.
This material is also chemically resistant to the effects of cement, mineral fertilizers, soap, soda and other compounds, but it can be damaged by the action of solvents such as white spirit or turpentine.
But this polymer is extremely unstable to sunlight and combustion. Under the influence of ultraviolet radiation, expanded polystyrene loses its elasticity and mechanical strength and eventually completely collapses, and under the influence of a flame it quickly burns out with the release of acrid smoke.
With regard to sound absorption, this insulation is capable of damping impact noise only when it is laid with a thick layer, and it is not able to extinguish wave noise.
The indicator of the ecological purity of the PPP, as well as its biological stability, is very insignificant. The material does not affect the state of the environment only if it has some kind of protective coating on it, and during combustion it emits many harmful volatile compounds such as methanol, benzene or toluene. Fungus and mold do not grow in it, but insects and rodents can settle. Mice and rats may well create their homes in the thickness of the expanded polystyrene plates and gnaw through passages, especially if the floorboard is covered with them.
In general, this polymer is very durable and reliable during operation. The presence of high-quality cladding to protect against various adverse factors and the correct, technically competent installation of this material is the key to its long service, which can last for more than 30 years.
Pros and cons of using PPP
Expanded polystyrene, like any other material, has a number of both positive and negative features that should be taken into account when choosing it for further use. All of them are directly dependent on the structure of a particular grade of this material, obtained in the process of its production. As mentioned above, the main positive quality of this heat insulator is the low level of its thermal conductivity, which makes it possible to insulate any building object with sufficient reliability and high efficiency.
In addition to the material's resistance to high positive and low negative temperatures, a significant advantage of this material is its very low weight. It can easily withstand heating to temperatures of about 80 degrees and resist even in severe frosts.
Softening and disruption of the structure of the material begins only in case of prolonged exposure to high temperatures above 90 degrees Celsius.
Lightweight slabs of such a heat insulator are easily transported and installed without creating a significant load after installation on the elements of the building structures of the facility. Without passing or absorbing water, this moisture-resistant insulation not only preserves its microclimate inside the building, but also serves to protect its walls from the adverse effects of atmospheric moisture.
Expanded polystyrene was also highly appreciated by consumers due to its low cost, which is significantly lower than the price of most other types of heat insulators on the modern Russian building materials market.
Thanks to the use of PPP, the energy efficiency of the house insulated by it significantly increases, reducing several times the cost of heating and air conditioning the building after installing this insulation.
As for the disadvantages of a polystyrene foam heat insulator, the main ones are its flammability and environmental insecurity. The material begins to actively burn at temperatures from 210 degrees Celsius, although some of its grades are able to withstand heating up to 440 degrees. During the combustion of PSP, very dangerous substances enter the environment that can harm both this environment and the residents of the house insulated with this material.
Expanded polystyrene is unstable to ultraviolet radiation and chemical solvents, under the influence of which it is very quickly damaged, losing its main technical characteristics. The softness of the material and its ability to store heat attracts pests who equip their homes in it. Protection against insects and rodents requires the use of special compounds, the costs of which significantly increase the cost of installing the heat insulator and the cost of its operation.
Due to the relatively low density of this insulation, steam condensing in its structure can penetrate into it. At temperatures down to zero degrees and below, such condensate freezes, damaging the structure of the heat insulator and causing a decrease in the thermal insulation effect for the whole house.
Being a material, in general, capable of providing a fairly high-quality degree of thermal protection of a structure, expanded polystyrene itself needs constant protection from various adverse factors.
If such protection is not taken care of in advance, then the insulation, which quickly lost its positive performance, will cause many problems for the owners.
For information on how to insulate the floor using extruded polystyrene foam, see the next video.