The difference between extruded polystyrene foam and expanded polystyrene foam

Polystyrene foam, extruded and regular polystyrene foam are considered one of the most popular materials used in many areas of construction, from insulation work to packaging of fragile goods. But when is it better to use polystyrene foam and when to use polystyrene foam? It is difficult for the average person, who rarely encounters repair and construction work, to determine how polystyrene foam differs from expanded polystyrene. First of all, it’s worth understanding what each of these materials is.

Production of polystyrene foam and expanded polystyrene

Polystyrene foam is a synthetic, plastic material. In essence, it is a small shell filled with gas. Made from different types of polymers. Thanks to this, it is possible to create types of materials with different properties.

So, you can find the following types of foam on sale:

polyurethane,
phenol-formaldehyde,
polyvinyl chloride,
urea-formaldehyde,
polystyrene.

Polystyrene foam made from different materials differs in technical characteristics and resistance to different types of influence (mechanical, chemical, influence of natural factors, etc.). Depending on the properties, the scope of its application differs, which allows you to choose the foam that is best suited for specific conditions. The most famous is polystyrene foam, or simply expanded polystyrene, since this type of material is most often used in domestic conditions.

Expanded polystyrene foam and expanded polystyrene are the same material. If you extrude the polymer, you get one of the varieties of expanded polystyrene - penoplex.

Types of expanded polystyrene

The vast majority of polystyrene foam is made from polystyrene. Widespread and long-known in our country, polystyrene foam is no exception. Therefore, it is incorrect to compare which is better, polystyrene foam or polystyrene.

However, foam sheets are available for sale, differing in appearance and structure. The reason for this is different production technologies. There are two main types of expanded polystyrene :

Pressless is the most common. It is this variety that foam is usually associated with. When this material was invented, it received the brand name “styropor”. It is produced by polymerization of styrene with the addition of a pore-forming substance. The high tendency to pore formation made it possible to achieve a flesh content of up to 98% in the gas composition. All the gas is contained in microscopic polystyrene cells.
Extrusion - produced by the extrusion method, that is, by pressure treatment at elevated temperatures with the addition of a foaming agent and subsequent extrusion from the extruder.

The porosity in these materials is different.
The main visual difference between styrofoam and extruded polystyrene foam is the porosity structure.
Extrusion makes it possible to achieve cells measuring several tenths of a millimeter, and classic polystyrene has spherical granules that are significantly enlarged during steam processing and are easily separated from each other. See also: technical characteristics of polystyrene foam.

It is impossible to unambiguously determine which is better, extruded polystyrene foam or polystyrene foam obtained using the non-press method. Each material has its own characteristics that determine its application.

Pressless material

The relatively large size of classical foam granules is determined by its manufacturing technology.

A simplified production process can be described by the following algorithm :

The starting material is styrene granules. At the first stage, the granules are initially saturated with gas; for this purpose, it is dissolved in the polymer mass. Traditional technology uses natural gas for this purpose. Widely used are pentane, isopentane, or mixtures thereof. They are highly volatile liquids, the vapors of which are used in production. The process is called suspension polymerization, since these liquids are highly soluble in styrene, but insoluble in polystyrene. Special fire-resistant modifications of the material are also produced, in which carbon dioxide acts as a granule filler. Sometimes vacuum technology can be used, in which there is no gas filler.
At the second stage, the granules are treated with steam. Alternative processes may use water or air treatment. During this exposure, the granules begin to grow significantly and can increase in size up to 30 times.
At the final stage, the granules are sintered while simultaneously filling the shape of the future product.

Comparison of manufacturing methods for polystyrene and polystyrene foam

Polystyrene foam and expanded polystyrene are made from the same material, but production technologies are very different . Conventional polystyrene foam is made by the “steaming” method. Microgranules of polymer material are placed in a mold and then exposed to water vapor. Under the influence of high temperature, the surface of the granules begins to increase, and larger micropores form on it. The impact continues until the foam fills the entire block mold.

Penoplex is made using the extrusion method. In this case, before extruding the material, it is first melted, then a foaming reagent is added. After this, you can extrude the mass - pass it through a special molding tool. In this case, the cells are filled with natural gas, or carbon dioxide if fire-resistant polystyrene foam is produced. This method of extruding the polymer makes it possible to achieve a more even structure of the finished material, since the cells remain closed.

Types of polymer insulation

Polystyrene foam and extruded polystyrene foam occupy a leading position in the popularity of materials used as insulation. The reason for this is that insulation made from such materials does not require ventilation. They both have a fairly dense structure and high vapor permeability. Moreover, these materials are good for their versatility. For example, Penoplex is used as insulation in both individual and mass construction. Polystyrene foam is very fragile , so it is suitable for external insulation.

Comparison of polystyrene foam and extruded polystyrene foam

Despite the similar composition, insulation materials are manufactured using completely different technologies, and therefore differ significantly in technical characteristics.

As you know, it is precisely this immovable air layer that provides good thermal insulation. The thermal conductivity of expanded polystyrene is lower than that of wood (3 times) and even lower than that of brick (17 times). Due to this feature, to insulate walls 21 cm thick, you will need an insulation board 12 cm thick.

Penoplex, due to its higher density, is superior to polystyrene foam in terms of thermal conductivity, but the difference is small. So, if the thermal conductivity of foam plastic is 0.04 W/mK, then the corresponding parameter for penoplex is 0.032 W/mK. If we talk about materials, then for thermal insulation, instead of a 25 cm thick polystyrene foam board, you can take a 20 cm thick polystyrene foam board, and the result will be the same. However, these indicators may vary depending on the manufacturer and the specific brand of materials.

The indisputable advantage of conventional polystyrene foam is its water resistance. The maximum volume of moisture absorption is no more than 3% of the mass of the material itself. Moreover, even with maximum moisture absorption, the characteristics of the foam do not change.

If you extrude the polymer, you can achieve even better results. Thus, the maximum moisture absorption rate for penoplex does not exceed 0.4%. Therefore, when insulating a façade with extruded polystyrene foam, vapor barrier can be neglected. If the choice fell on polystyrene foam, then it is better to carry out a vapor barrier.

If we talk about strength, then penoplex wins here as a denser material. Due to large micropores, foam plastic inevitably reduces its resistance to various influences over time.

The compressive strength of polystyrene foam is only 0.2 MPa, while that of extruded polystyrene foam is 0.5 MPa. If we compare the compressive strength of two slabs of the same thickness, then the foam plastic turns out to be 4 times less strong.

Comparative characteristics

Based on the above information, it is possible to make a complete comparison of these insulation materials, as a result of which it will be possible to answer the question: is polystyrene foam or not? Thus, expanded polystyrene has low thermal conductivity, which ensures heat retention inside indoor buildings. For polystyrene foam this figure is significantly lower. This circumstance affects the cost of products.

Important! Expanded polystyrene is a fairly durable material. It can withstand extreme loads over long periods of time. The moisture resistance of the material is also at the highest level, which cannot be said about polystyrene foam.

However, the weak link in the characteristics of insulation materials is their flammability. Both products will not be able to provide reliable safety during a fire without additional processing.

Shrinkage of materials is of no small importance when choosing. The higher this parameter, the worse the performance of the insulation. In this comparison, foam loses again. It is easily deformed under external loads. It also does not tolerate exposure to sunlight.

Expanded polystyrene has all the qualities of a suitable insulation material. This circumstance is influenced by the manufacturing methods of the product. Thus, this material is somewhat similar to foam, but it does not crumble.

Myths about the use of thermal insulation materials

We are breathing poison. There is an opinion that with prolonged use of polystyrene foam, decomposition occurs with the release of toxic substances. If you look at it, polystyrene foam, for example, is 98% air. A study was conducted in which scientists tested an insulated 30-year-old house and found that the material samples showed no signs of styrene decomposition. This means that this statement that poison will emanate from the insulated surface is another fiction.
These are quickly perishable materials. Probably everyone has heard that products made from polystyrene foam quickly deteriorate. Laboratory studies have shown that polystyrene foam boards can withstand more than 80 years of operation. Mechanical impact and ultraviolet radiation can lead to premature destruction of penoplex. Therefore, the better you hide the foam from the sun, the longer it will last you.

Summarizing all of the above, you can come to a conclusion and get a reasonable answer to a difficult question: polystyrene foam or extruded polystyrene foam - what to use?

In the video below, foam plastic as insulation is analyzed in great detail. If you watch it to the end, I think you won’t have any more questions about foam plastic.

Expanded polystyrene is superior to even the highest quality polystyrene foam in all characteristics, so it is better to use it in facade insulation. But the price is more expensive.

Advantages of conventional polystyrene foam

Ordinary polystyrene foam is slightly cheaper than styrodur, but you need to take into account that its characteristics are no worse:

Thermal conductivity – 0.039 W/μ. Due to good thermal conductivity, it is possible not to use thicker material.
A long service life, if the sheet was not initially defective, and it has certificates, and the supplier stored it correctly.
It goes out on its own when it catches fire.
Light weight and low price.
Density - 15-35 kg/m3, well suited for insulating walls outside, however, if the load is too heavy, it can crumble.
It is easy to install - it is simply cut, light in weight, and takes the desired shape when cut. All this does not take much time and does not require additional heavy equipment.
Multifunctionality, that is, this material can be used to insulate a wide variety of structures: balconies, roofs, walls, floors and much more.

How to make the right choice?

When insulating the walls of a house or apartment, balcony or loggia, we pursue the goal of retaining the greatest heat in the living space and preventing heated air from escaping outside. At the same time, the resources used for heating are reduced by almost a quarter, which also creates financial savings. Naturally, with this approach, paying money for materials that are not suitable is inappropriate, because when redoing the work, no savings will be achieved, and the time and nerves spent will cost many times more.

For our selection, manufacturers present different types of insulation, mineral, polymer and using plant materials. All insulation materials have different manufacturing technologies, they all have different thermal conductivity and special characteristics.

Advantages and disadvantages

Today, extruded polystyrene is known as a reliable and practical material that you can trust. Its relevance is due to many positive qualities, which should be discussed in more detail.

This material is waterproof. In case of unfavorable contact with liquid, the polystyrene foam floors are filled - no further movement of moisture occurs.
Extruded polystyrene foam is characterized by a low level of thermal conductivity. If we compare it with other insulating coatings, we can conclude that the thermal conductivity coefficient of EPS is less than or equal to (the only exception to the rule is polyurethane foam).
A characteristic feature of EPS is low vapor permeability. The coefficient of this parameter is considered to be the minimum among insulating components.
Expanded polystyrene is not subject to deformation even after a very long time.

This material is not afraid of temperature changes. In such conditions, it does not lose its useful qualities and remains just as practical/effective. Its operating temperature ranges from -100 to +75 degrees.
Installation, as well as dismantling of polystyrene foam, is not a difficult task, and it does not take as much time as many people think.
This material boasts a long service life, during which it does not deform or lose its qualities.
During operation, extruded polystyrene foam is not subject to destruction.
Extruded polystyrene foam is not afraid of inorganic solvents.
Working with this material is very easy and simple, since it is light in weight and thin.

This material is relatively inexpensive. Many consumers will be able to afford it. In this case, the price-quality ratio cannot but rejoice.
When laying EPS, you can do without the use of additional hydro- and heat-insulating coatings, which will significantly save money.
According to experts, XPS is not dangerous to human health. Moreover, when working with it, the master will not experience allergic reactions.
This material is not afraid of low temperatures, so it is ideal for being in the harsh and changeable Russian climate.
The durability of extruded polystyrene foam is also confirmed by the fact that it is not susceptible to rotting - not every building and finishing material can boast of this quality.

As you can see, EPS has a lot of advantages. That is why today it occupies one of the leading positions in the market of insulating materials. However, such a practical and reliable coating also has its drawbacks, which you should also be aware of before purchasing it.

This material is subject to combustion.
When exposed to temperatures above 75 degrees, polystyrene foam can release harmful substances that are hazardous to human health.
According to experts, this material is afraid of contact with infrared rays.
EPS can harbor mice, although many manufacturers deny this fact.
When interacting with various solvents, this material can be destroyed.

If the listed disadvantages do not scare you, then you can safely move on to purchasing this modern material - it is used in many areas.

1.5 Tendency to shrink

Shrinkage, like moisture absorption, is the main enemy of any insulation. When the material shrinks, cracks appear in the thermal insulation structure, which significantly reduce the overall insulation efficiency.

One of the main problems of polystyrene foam is its tendency to shrink when heated. Deformation manifests itself to a greater extent when the product is heated; therefore, it is better not to use polystyrene foam for thermal insulation of heated floor systems, and when insulating a facade with polystyrene foam, the insulation must be covered with white plaster, which protects from UV rays.

Things are much better with extruded polystyrene foam; the material practically does not shrink under any operating conditions.

Components of polystyrene foam beads

1.3 Hydrophobicity

The ability to absorb water is an important characteristic of any thermal insulation material.

In high-quality insulation, this property should be minimized, since when moisture accumulates, the insulation is prone to losing its thermal insulation characteristics, increasing weight and, with constant exposure to a humid environment, rotting and destruction.

Extruded polystyrene foam has a closed-cell structure, as a result of which the material has virtually zero moisture absorption. Unless it's defective. Therefore, we recommend buying insulation in Moscow to avoid defects.

When completely immersed in water for 24 hours, extruded polystyrene foam absorbs liquids no more than 0.2% of its volume, while this figure does not actually increase with a longer stay of the material in water - when immersed for 30 days, expanded polystyrene absorbs 0.4% of the volume.

Due to the structural differences in polystyrene foam, this indicator is much worse - in 24 hours the material, when fully immersed, absorbs 2% of the volume, when immersed for 30 days - 4%.

Structure of extruded polystyrene foam

This difference in performance is more than significant, especially if the insulation will be used in difficult conditions in terms of humidity. When insulating the basement, foundation and facade, extruded polystyrene foam performs much better.

Areas of use

In modern realities, extruded polystyrene foam is most often chosen, since ordinary polystyrene foam can release toxic substances when burned, but its external use is justified by the fact that foam has greater moisture absorption. Internal insulation is not recommended with either styrodur or polystyrene foam, since toxins can be released constantly, and not just when ignited. This is due to the fact that the material is initially processed with special mixtures.

Styrodur is well suited for insulating balconies, since you want to save space on the balcony, and not make it smaller. This material is usually about five centimeters smaller than regular material, but it performs excellently in preserving space and performing functions. In addition, styrodur is suitable for insulating foundations and basements, as it withstands mechanical stress quite well.

Insulating a house - what material to choose?

The warm season is exactly the time when it is necessary to solve global construction issues. The most important of which is façade insulation. This question is asked by both apartment owners and private home owners. Both new buildings and houses about 50 years old are insulated. When you have already decided to insulate your house, the question immediately arises, which confuses many, what to choose from these two materials.