Polyurethane foam: types and properties

Among various multifunctional building materials, polyurethane foam has been popular for a long time. This composition is used in various areas of repair, but not everyone knows what varieties this product has and how to properly use foam in the repair process. In order not to make a mistake in choosing a product, you should carefully read a number of recommendations for its use.

Polyurethane foam is a substance that is a fluoropolymer sealant with a special consistency that changes during direct use. Also among the components of the mixture can be found polyol and isocyanate. The products are produced in special cans, the contents of which are under pressure. A propellant is used to form a foamy substance due to the high pressure.

A feature of this sealant is a change in the state of aggregation under certain conditions. This process occurs due to the contact of the foamy structure with moisture in the air and on the treated surface. Thanks to this contact, the polyurethane foam hardens, polymerization occurs in its composition.

Such a sealant has a number of special characteristics that distinguish it from other compounds used in the process of construction and repair. During the operation of the foam, the volume of the substance release is taken into account, which is measured in liters. This indicator is determined by the consistency of the foam (foaming), as well as the amount of substance that came out of the container.

The adhesion index characterizes the adhesion strength to the substrate. Various surfaces can act as a substrate, the most common are brick, concrete, plastic, wood. Adhesion values ​​are very high with these materials, but with substrates such as oily surfaces, silicone, ice and synthetic materials, there is practically no adhesion.

Foaming is characterized by the boiling process of the substance in the container. It occurs due to the difference between atmospheric pressure and the pressure inside the cylinder. When the substance leaves the package, bubbles form. Due to the presence of silicone particles in the composition, the foam mass retains a certain shape. Lack of silicones can lead to a violation of the consistency of the composition when foaming.

The existence of porous components allows the bubbles to burst, while the contents of the bubbles do not leave the foam clot. Only excess propellant is removed naturally. There should always be a balance between the number of closed and open bubbles, its absence can radically change the structure and properties of the composition.

Expansion is a chemical process that occurs after foaming. It is the reaction of the prepolymer to the environment. As a rule, the foam substance comes into contact with moisture, during which carbon dioxide is released and polyurethane compounds are created. It is at this stage that the substance expands, filling the required areas. It is believed that foam manufacturers must carefully control this process so that excessive expansion does not occur, but many think that this property can significantly save material consumption during the repair process.

Secondary expansion is a process that occurs after the substance has polymerized. Most often, this process is precisely negative, since it affects the ease of use of the composition. Re-expansion can most often occur due to the influence of external factors, for example, an increase in temperature. But an important indicator is the origin of the gases that the manufacturer adds to the foam. Quality products, as a rule, are not subject to spontaneous expansion or shrinkage.

Some builders have noticed that the likelihood of secondary expansion increases with products that are produced in cylinders with a tube.

An important indicator of quality is the viscosity of the substance. It significantly determines the consistency of the composition and the degree of influence of temperature factors on it. With a sharp change in temperature, the viscosity is often violated.

The polyurethane foam has special thermal insulation properties. Its thermal conductivity is not very different from that of foam. Foaming agent is great for insulation, but it is usually used on a small area or on certain seams, because it will be quite expensive to insulate large spaces with foam.

Depending on the type of composition, the foam can have a different density. It is chosen in accordance with the type of planned work, because this indicator varies for different procedures.

The characteristic color of the foaming sealant is light yellow. If the surface is not properly prepared, the color can change under the influence of sunlight and turn orange. This process significantly affects the life of the material. To prolong it, treat the material with putty or plaster.

The shelf life of products depends on the manufacturer. But on average, it varies from one to one and a half years. After this period, it is not recommended to use a sealant, because due to a change in properties, it can present surprises during operation.

When buying construction foam, it is very important to choose exactly the composition that you need, because sometimes it is easy to confuse product types. Therefore, it is necessary to understand in advance the classifications of types of polyurethane foam according to certain criteria.

The first sign that characterizes the sealant is the number of components in the composition.

• One-component formulations. These include exactly those products that are sold in cylinders ready for use. This foam has the standard characteristics outlined above. The second name for disposable formulations in aerosols is household foam. These products are characterized by a lower filling density of cylinders in comparison with professional formulations.
• Two-component foam includes more complex components that need to be additionally prepared before carrying out installation work. This foam is intended for a special construction gun.

But since it will be laborious and expensive for people who do not have much construction experience to use such compositions, they are in demand mainly among experienced craftsmen. This professional foam is not disposable.

Another sign of the classification of polyurethane foam is its resistance to various temperatures.

There are several varieties.

• Summer. It is used at positive temperatures - from 5 to 35 degrees Celsius.
• Winter. It is used in cold weather conditions - at temperatures down to -20 degrees Celsius. This variety has a weaker expansion, which is its negative quality.Also, in order to ensure better adhesion of the composition to the surface, it is sometimes necessary to wet it from a spray bottle. In order for the foam to function normally, you need to monitor the temperature of the cylinder, which should not fall below 20 degrees, even in the cold season.
• All-season products it is used in a wide range of temperatures - from 10 degrees below zero to 30 degrees Celsius.

It is often necessary to use a foam sealant in extreme conditions where there is a risk of fire.

According to the degree of resistance to fire, several types of compositions are also distinguished:

• B1 - this class indicates that the composition is highly resistant to open fire.
• B2 is an indicator that the material is capable of self-attenuation.
• B3 characterizes foam that is not heat resistant. This group includes a type of sealant such as waterproof foam. But it does not deteriorate under the abundant influence of moisture and is ideal for use in bathrooms and swimming pools.

Construction foam has a number of important functions:

• sealing;
• soundproof;
• mounting (connecting);
• heat insulating.

Each of these functions is implemented in a specific area of ​​use.

The main areas of application for building foam sealant include the following:

• Warming of premises of an economic nature. Polyurethane foam is often used to seal cracks when insulating garage doors or warehouses.
• Fixation of doors, wall panels, windows.
• Due to the fact that this material is characterized by additional waterproofing and soundproofing of the room, it is often used to fill various gaps when carrying out major repairs in residential premises.
• The material is often also used as an arches fastener in the interior.

Very important for both professionals and inexperienced builders is such an indicator as the consumption of assembly sealant. This criterion directly affects the amount of material required for repair work, so it is important not to make a mistake when calculating the consumption.

There are a number of factors that affect the amount of foam used.

• Air temperature during operation of the composition. It can provide additional expansion and material savings.
• It is important to consider the material of the surface to which the foam is applied. The level of adhesion of the sealant and different raw materials is not always the same. Some surface absorbs moisture better, and some repels water. All this affects the quality of functioning of the foam composition and its consumption.
• Features of the production of sealant. In most cases, the manufacturer produces construction foam with a certain rate of primary expansion. He is obliged to indicate this data on the packaging so that it is more convenient for the buyer to calculate the amount of material required. For honest manufacturers, consumption rates always coincide with reality.

The standard solution output is 50 liters, which is directly proportional to the filling of the joint, which does not exceed two centimeters in width and 5 cm in depth. An important indicator of consumption is the area that must be treated with a sealant. If it does not exceed 3 square meters, then the flow rate can be more than 7 m3, which is equivalent to 123 cylinders. But if the surface occupies more than 3 m2, then the consumption is reduced.

The key step is to use polyurethane foam. It is imperative to read the instructions for use of the composition.

Its application includes several stages.

• If you do not want to spend a lot of time washing your hands after completing the work, wear rubber gloves. They will protect you from the inevitable skin impurities.
• The cap must be removed from the cylinder and, depending on the type of device, a special tube must be connected to the valve or the gun must be screwed on.
• To make the consistency of the substance in the container homogeneous, it is recommended to shake the composition thoroughly. Shake should be at least 60 seconds.
• The surface where the sealant will be applied should be treated with water.
• The container should be held so that it is located upside down, since this is the best foam delivery.
• Moving from top to bottom, fill in the gaps by 1/3. The remaining space will be filled during the expansion process.
• When the foam fills all the empty areas, it is recommended to spray it with water. This will speed up the final hardening process.

The time it takes for the foam to acquire a hard and dry texture is different and depends on several indicators:

• The manufacturer creates foam of various qualities. You can buy products that dry in different amounts of time.
• In order not to translate the product, remember that there are different types of drying, and each of them requires a certain amount of time. The surface layer hardens after about 20 minutes. You can only use the tool to remove excess foam after 4 hours, and the final hardening will take place no earlier than 24 hours.
• To speed up the drying time, not only the base is sprayed with water, but also the applied composition itself.

There are a number of companies producing polyurethane foam, which occupy a leading position in the world rating of manufacturers.

German firm Dr. Schenk is known throughout Europe and has many branches in various countries, including Russia. The company manufactures compounds for both indoor and outdoor use. All products combine quite an acceptable level of quality and affordable prices.

Estonian company Penosil manufactures polyurethane foam with a fairly wide range of applications. Such products are often used not only in the construction and repair of housing, but also in various industrial structures. With their high density and low level of expansion, the compounds will be an excellent option for working with door surfaces.

High quality construction foam is produced by a Belgian company Soudal... A distinctive feature of this company is the constant striving to improve its products. More and more new technologies are regularly applied to make the sealant as convenient to use as possible. The product range is also mind-boggling.

Brands from Russia are not inferior to foreign companies. Company Realist produces both professional and semi-professional formulations that can be used for various types of work and temperature conditions.

Firm Proflex famous for the manufacture of exclusively foam sealants. Among them there is a special line of products for external work. Many professionals in the field of construction and repairs note that the products of this company are almost identical to the quality of leading European brands.

Compositions of the company are distinguished by exceptional quality Makroflex... It is noted that the foam does not crumble after drying, does not crumble and does not lose its original appearance for a long time.

In the operating instructions for the polyurethane foam, far from all the nuances of working with such a material are taken into account.

The recommendations of professional builders will bring significant benefits when working with a sealant and its choice:

• The rate of solidification of the composition is significantly affected by the level of humidity in the room. If the microclimate in the room is dry, then solidification will take longer.
• If you are filling small joints or gaps, be sure to buy low-expanding foam, which will save you the trouble of scraping off excess material and will help you fill the joints as neatly as possible.
• A construction gun in good condition can store the foam composition inside itself for no more than 3 days.

• Pay attention to the appearance of the balloon. If there are traces of deformation on it, this may mean that the composition is stored under inappropriate conditions.
• When choosing a gun for assembly sealant, it is better to stop at metal models that have a collapsible design. Such options are convenient to use and at the same time are relatively inexpensive - about 500 rubles. For many, the highest priority is the material of the device, such as stainless steel. Pay also attention to the presence of a regulator that determines the degree of foam solution delivery.
• If you have a large scope of work with construction foam, it is recommended to purchase a special cleaner for such material. The following components are included in the purifier: acetone, dimethyl ether and methyl ethyl ketone. All these components are enclosed in a special aerosol can, which also comes in the form of a nozzle for a gun.

• If you decide to fill the crevices with foam, then make sure that their thickness does not exceed 5 centimeters. Otherwise, you may get too high a consumption of material or an unpredictable change in composition, for example, excessive expansion.
• If the foamy composition gets on your skin or clothing, it is recommended to immediately wash off the dirt, otherwise it will be much more difficult to do as the material dries.
• Despite the fact that the assembly sealant does not allow water to pass through, but retains it inside its texture when absorbed, many experts recommend using foam only for interior decoration. Before deciding on an exterior finish, analyze the features of the climate.

For wall insulation with polyurethane foam, see the following video.