Polyurethane foam characteristics, properties and application

Polyurethane foam is also called polyurethane foam. This is a universal sealant for filling cracks, improving sound insulation, and insulation. On the market you can find dozens of manufacturers of sealing materials that differ from each other in properties, technical features, viscosity, strength, adhesion and other criteria.

The basic components of polyurethane foam are isocyanate and polyol. Under the influence of additional components, a chemical reaction occurs, as a result of which it is possible to obtain the necessary properties to solve the assigned construction or repair problems. Initially, rigid foam was made from the above components, then a technology of flexible consistency was developed, and only in the end they were able to produce semi-rigid polyurethane foam. It is suitable for sealing and foaming cracks of various sizes.

Mounting foam one or two-component material

Content

based on polyurethane foam, used for filling joints and seams in installation and construction work. Performs the functions of sealing, thermal insulation, sound absorption, fixation.

Among the popular manufacturers of polyurethane foam, distinguished by good adhesion, uniform structure, and declared foam yield, European brands are leading.

Finnish foam Macroflex is one of the most famous, versatile and affordable products. Reputable and high-quality brands include Tytan (Poland), Penosil (Estonia), Soudal (Belgium).

Comparison of insulation materials

Choosing the best of the three presented insulation materials is not difficult; you just need to compare the technical characteristics of the materials.

Thermal conductivity

A characteristic showing the amount of heat passing per unit of time (second) through 1 square meter of material at a unit temperature gradient.

Comparison of thermal conductivity coefficients of insulation:

• PIR boards and sprayed polyurethane foam 0.022 W/m°K;
• Foamed foil polyethylene 0.038 – 0.051 W/m°K.

The thermal conductivity of PIR is comparable to PUR insulation and much lower than that of other thermal insulation materials. Foamed polyethylene has half the thermal insulation properties of PIR and PUR.

The lower the thermal conductivity of the material, the correspondingly better the heat saving or energy efficiency indicators. By using insulation with record low thermal conductivity to insulate a house, bathhouse or other room, you can save free internal space by reducing the thickness of the material. In addition, energy-efficient insulation quickly pays for itself financially, as the costs of heating and air conditioning rooms are significantly reduced.

Logicpir slabs are laminated with vapor-proof aluminum foil

Compressive strength and stiffness

Rigidity, strength, and lack of deformation under high loads allow the material to be used not only for insulating floors under heavy wet screeds, but also on existing roofs, including in regions with high snow loads.

The compressive strength at 10% deformation for PIR slabs is 150 kPa or 15 tons per 1 sq. m. meter. Polyisocyanurate foam does not wrinkle or crumble throughout its entire service life, the geometric dimensions are stable even under high loads.

PIR boards are used in the construction of existing roofs of all types

Foamed polyethylene has a compressive strength 4 times lower and is only 35 kPa.

The rigidity of the material is no less important when insulating walls. If the insulator breaks during the period of operation, the upper part of the walls will remain uninsulated, which will lead to a number of problems, one of which is a significant increase in the cost of heating the premises.

Insulation can lose its rigidity under the influence of moisture, mold, pests and other factors. The conclusion follows - a high-quality material, such as Logicpir, is distinguished not only by rigidity, but also by biological stability, a minimum percentage of moisture absorption, and biological and chemical inertness.

Logicpir slabs can be installed without much labor

Fire safety

Polyisocyanurate foam insulation (PIR) belongs to the G1 flammability group. High fire-technical characteristics of both the slabs themselves and insulated structures are achieved thanks to the theoreactivity of the polymer. Under the influence of flame, the top layer of insulation cokes, that is, it turns into a charred crust (porous carbon matrix), which prevents the further spread of fire.

PIR board - test by fire

Foamed polyethylene cannot be called a fireproof material. This material belongs to thermosets - chemical polymers that, when exposed to flame, turn into a burning melt.

Having compared insulation materials, it is not difficult to understand why PIR boards are so in demand in the world. More than 40% of roofs in Western Europe and more than 76% in North America are already insulated with polyisocyanurate boards. The technical characteristics of the material are close to ideal, this makes it in demand in residential, commercial, industrial construction, and agriculture (during the construction of agro-industrial and livestock complexes).

Polyurethane foam - composition

Polyurethane foam on the market is presented in one-component and two-component mixtures. Moreover, its overwhelming share belongs to one-component sealant.

The foam includes two main components - MDI and polyols. Mixed in a pressure cylinder, they turn into a one-component liquid prepolymer. When leaving the container under the action of the propellant gas (propellant), the substance enters into a polymerization reaction with water molecules present in naturally humid air.

Foaming occurs, the volume of the mass expands by 3 or more times, and the formation of a densely elastic durable substance with a porous structure - polyurethane foam. It will take approximately 24 hours for the reaction to complete and to cure completely.

In a two-component composition, an activator is added to the base (prepolymer). Being in the same cylinder, they are separated by a shutter and do not mix. When the lock is removed, activation and rapid polymerization occurs, independent of air humidity. The mass begins to harden immediately in the container.

The process lasts from three to ten minutes. In this short time you need to have time to use the entire composition. It takes 4 hours for the foam filler to completely harden. Considering the need for quick, skillful manipulations, it is advisable for specialists to work with this product.

In addition to the base and a mixture of liquefied gases (propane-butane), various additives are added to the foam composition to impart certain properties (fire resistance, increased adhesion): stabilizers, plasticizers, surfactants and others.

Volume of polyurethane foam in the bolt

Peculiarities

Polyurethane foam has become such a widespread attribute of modern construction and renovation that it is hard to imagine how we once worked without it. Cylinders with an easily blown and instantly swelling reagent provide:

• thermal insulation;
• sound damping;
• vibration suppression;
• sealing connections and joints;
• bridging gaps;
• saturation of inaccessible cavities.

Polyurethane prepolymers are displaced from the cylinder with a special gas. The initially ejected substance is light and full of fine pores. But inevitable contact with air accelerates the polymerization process and the transition of polyurethane into the form of polyurethane foam. Simultaneously with the chemical transformation, the foam also changes physically, it takes up more and more space, hardens and freezes. Such a unique substance is extremely useful, but in order to achieve success, you should carefully study its technical characteristics.

The key parameters of any polyurethane foam are:

• displacement of the ejected mixture (the numbers given on the cylinder refer to an ideal situation);
• output expansion level;
• re-expansion (experienced by a substance during polymerization);
• number of pores;
• adhesion to surfaces;
• viscosity.

It has long been known that polymerized foam can take up many times more space than foam that has just left the factory tank. Inexperienced or inattentive builders often cause serious damage for this reason. First of all, the risk concerns doors and windows, where a significant mass can press on a relatively thin structure. Professionals know that when a cavity is saturated, it is allowed to immediately direct a maximum of 1/3 of its volume there. If voids remain later, this can be corrected by adding additional foam mass, but only after hardening.

The density of polyurethane foam is closely related to its expansion coefficient. The strongest and most stable seams are obtained by using a material with the least secondary swelling. But the downside of this choice is ultimately increased mixture consumption. If the surface of the surrounding structures is quite hard, you can use actively swelling foam to save money. As for the formation of pores, this indicator directly affects the stability of the connection of the foam with other surfaces.

A high-quality reagent should have at least 88% blocked pores. Another valuable property is its excellent adhesion to almost all widely used materials.

But it is important to remember that even the best polyurethane foam does not stick to:

• silicone;
• polypropylene;
• polyethylene;
• Teflon.

Viscosity is also quite important for practical purposes; it is even used to judge whether the job will be done efficiently or not. Good viscous foams do not creep down under their own weight and are perfectly retained on the treated surface. But there is a nuance here: if the temperature is higher or lower than the critical one for a given mixture, the viscosity can change significantly. This can be compensated for by wetting the surface to be treated before starting work to increase adhesion. It’s even better to work at the temperatures indicated on the packaging.

Drying time in most cases ranges from 8 to 15 minutes. But it is still recommended not to touch the foam for at least 24 hours. When the surface has hardened, you can cut off part of the layer and cover it with plaster or paint. Normal shrinkage does not exceed 5%; if it is more, the polymerizing material may be deformed and torn. Then there is no need to talk about high-quality sealing. Additionally, it is worth learning everything about:

• shelf life and service life of the coating;
• fire resistance level;
• compressive stress;
• coefficient of thermal conductivity;
• shear strength.

Polyurethane foam - performance properties

• primary expansion

This is a beneficial increase in volume after applying foam to the gap. Due to the presence of expansion, experts recommend filling joints and seams by a third.

The increased volume will occupy the entire space and compact the foam itself, giving it the properties of a reliable retainer and damper.

• secondary expansion and shrinkage

Negative consequences can be considered secondary expansion or shrinkage after polymerization of the top layer.

After completion of polymerization of the surface layer, high-quality foam ideally represents a stable inert mass of constant volume. In fact, often due to violations of the application technology (increased ambient temperature, uncleaned surface, extraneous physical influence) and poor-quality composition, a secondary change in volume can occur - either its subsequent increase or shrinkage.

Polyurethane foam expands a second time due to the expansion pressure on the structure and can deform and change the geometry of window blocks, door frames, and partitions. Shrinkage will result in leaky gap filling and weak sealing, which will require repeated insulation work. The shrinkage rate for the best samples is close to 5%.

Applying foam using a foam gun

Polymerization speed of polyurethane foam

Drying of the surface layer at a relative humidity of 65% and a temperature of 20°C occurs after 20 minutes, that is, during this time the useful volume of released foam accumulates. After 4 hours the sealant can be cut off. It will take up to 24 hours for the polyurethane foam to fully cure.

Adhesion

Characterized by excellent adhesion to most building surfaces: wood, concrete, metal, glass, stone, PVC. The foam adheres perfectly to surfaces with any roughness and curvature. However, there are no adhesive properties with inert and oily bases - polyethylene, silicone, and ice.

Heat resistance

Conventional hardened polyurethane foam, classified as class B3 according to the German standard DIN 4102, can easily withstand temperatures from -40° to 90°C, and briefly 130°C.

Samples marked with class B2 are self-extinguishing and do not burn.

Class B1, which includes fire-resistant foam, is resistant to fire. This material is fire resistant up to 240 minutes.

Fear of UV rays

The polyurethane foam base is resistant to many chemicals, moisture, and putrefactive bacteria, but under the influence of ultraviolet radiation it quickly darkens and collapses.

Therefore, it requires protection in the form of applying layers of primer, painting, or in another way that excludes direct contact of the polymer with sunlight.

Advantages and disadvantages

Foam material is much easier and simpler to use to achieve any of your goals than most other materials. It is safe for humans and pets, mechanically strong and almost does not cause allergies. It is good to use the professional option, because guns significantly increase the penetrating power of the material. But the household variety is much better suited for minor work. Even when the atmosphere around is very humid, the temperature constantly changes within wide limits, the foam stably withstands such influences.

Expert studies have shown that 1 cm of polyurethane sealant, after hardening, retains heat to the same extent as 1.5-1.9 cm of polystyrene. For mineral wool this coefficient is 1.8. Using just one cylinder of a standard capacity, you can easily install two or even three windows or one door (unless it is absolutely gigantic in size, of course).

Types of polyurethane foam

According to the method of execution, polyurethane foams are divided into:

• professional;
• standard (household).

The professional sample is equipped with a valve and a ring, the design of which allows you to work using a special gun for polyurethane foam . This device can regulate the output of the foam composition, penetrate into hard-to-reach places, saving the consumption of raw materials.

Cylinders are available with a capacity of 1000 ml for large volumes of work. The structure of the frozen polymer is fine-cellular, homogeneous, secondary expansion is either absent or very small. Unlike household foam, it is denser, hence the quality of the joint is better, which is why professional installers use professional foam.

Household units are equipped with a plastic tube with a lever that opens the valve. They are produced in smaller capacities, are much cheaper, and are easy to use. The composition that is not completely used is suitable for a month.

It happens that the manufacturer places less demands on this type of product. As a result, the formation of voids, heterogeneity, and significant secondary expansion can be observed in a hardened sealant of this type.

According to application, depending on the ambient temperature, three types of insulating material are distinguished:

• summer with a temperature range from +5°C to +30°C;
• winter, from -18°C to +25°C;
• all-season, from -10°C to +25°C.

Compliance with these temperature conditions when using each type of sealant will allow you to obtain a large yield of polyurethane foam and rapid curing.

There are special types of foam with improved properties:

• fire-resistant foam - fire resistant (class B1 DIN 4102);
• with a universal application system (gun plus tube);
• with enhanced fastening function (foam-cement).

Adviсe

The operating instructions for polyurethane foam do not take into account all the nuances of working with such material.

Recommendations from professional builders will bring significant benefits when working with sealant and choosing it:

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

Pay attention to the appearance of the cylinder. If there are signs of deformation on it, this may mean that the composition is stored in inappropriate conditions. When choosing a gun for mounting sealant, it is better to choose 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. Also pay attention to the presence of a regulator that determines the degree of supply of the foam solution. If you have a lot of work to do with construction foam, it is recommended to purchase a special cleaner for such material. The cleaner contains the following components: acetone, dimethyl ether and methyl ethyl ketone. All these components are contained in a special aerosol can, which is also available in the form of a gun attachment.

• If you decide to fill the cracks with foam, make sure that their thickness does not exceed 5 centimeters. Otherwise, you may end up with too much material consumption or unpredictable changes in composition, such as excessive expansion.
• If the foam composition gets on your skin or clothing, it is recommended to immediately wash off the contamination, otherwise it will be much more difficult to do as the material dries.
• Despite the fact that the installation sealant does not allow water to pass through, but retains it within its texture when absorbed, many experts recommend using foam only for interior decoration. Before deciding on exterior decoration, analyze the climate.

For information on insulating walls with polyurethane foam, see the following video.

GOST polyurethane foam - technical characteristics

Components for the production of polyurethane foam

For the production of polyurethane foam, mainly three types of components are used:

• Components for hard
• Components for elastic
• Components for integral

All components are characterized by such basic parameters as start time and density. Start time – the time at which the components begin to increase in volume (foaming).

Hard is obtained by spraying and pouring. Components for spraying polyurethane foam are characterized by minimal start time. Therefore, during the production of polyurethane foam, instant foaming and hardening of the mixture occurs. For spraying, it usually uses components with a density of 30 to 60 kg/m3.

Rigid, used for molded products made of polyurethane foam, pre-insulated pipes and decor, is characterized by an increased start time. This allows the mixed components to be in a liquid state and have time to fill the entire mold or the required volume. The start time for such components reaches 80 seconds (while for spray-coated systems the start time is 3-7 seconds).

Application of polyurethane foam

Foam filler is indispensable for sealing and sealing butt seams when installing window profiles, window sills , door blocks, roofs, structural panels, SIP panels .

Used to insulate openings during communications and pipes.

Fixes foam plastic as a fastening material during insulation work.

Can act as soundproofing screens and thermal insulation.

Equipment for spraying polyurethane foam

The following types of polyurethane foam are distinguished:

• Open cell. Polymerizes due to moisture. Water vapor penetrates into the structure, the final product is vapor permeable. Used as soundproofing installation material;
• Closed cell. Has high vapor resistance. It is used as a durable vapor and waterproofing material.

The method is based on obtaining polyurethane foam from two components. When polyol and polyisocyanate are mixed, polyurethane foam is formed. When sprayed, the mixture foams, increases in volume and hardens. Professional equipment makes it possible to mix components in precise proportions at the required temperature and spray the resulting liquid polymer using a spray gun for polyurethane foam onto the surface under a certain pressure.

Installations (devices) for spraying polyurethane foam are divided into high- and low-pressure foam generators. In a high-pressure apparatus, its value can reach 260 bar.

Equipment for applying polyurethane foam consists of:

• Two liquid pumps;
• Electric motors that drive them;
• Compressor;
• Electronic control unit.

Additionally, it can be equipped with supply tanks for raw materials with an electric heating function.

Using electric motors, pumps supply components for spraying polyurethane foam into the mixing chamber of the spray gun in the required proportion. After mixing, the finished mixture is sprayed onto the surface to be treated. The intensity of its supply to the spraying device can be adjusted.

Thorough mixing of the raw materials and ejection of the finished product from the nozzle of the gun occurs with the help of compressed air. The compressor capacity must be at least 350 l/min. With lower parameters, the mixture is not mixed well enough and the quality of the foam decreases. The nozzle of the spraying device becomes clogged with unreacted components of the mixture.

Using the spraying method, polyurethane foam is applied to any material: wood, glass, metal, concrete, brick, painted surface. The coating is inert to chemically active environments, so it is used as a roofing and anti-corrosion material. Density varies from 30 kg/m³ to 200 kg/m³.

Each new layer is sprayed onto the previous one after it has hardened. The layer thickness is 10–15 mm. Sufficient heat and waterproofing is provided by at least three layers.

Spraying is used for:

Manufacturers of casting complexes for polyurethane foam processing

Video description

This video talks about TechnoNIKOL 65 Constant polyurethane foam and demonstrates how it works:
DEXX is an all-season foam for household and professional work. The working mass copes with filling and sealing voids and provides good sound insulation. The yield reaches 30 liters of foam, but this disadvantage is compensated by technical characteristics.

DEXX Source 220-volt.ru

IRFIX B1 is designed for work in conditions of increased fire hazard. As a rule, it is used to lay electrical cables and install doors and chimneys. The lack of toxicity allows the use of foam inside the house. Characteristic properties: secondary expansion is low, adhesion is high.

IRFIX B1 Source molstroi.ru

Sealant - a jack of all trades!

Insulating a home is the first thing that comes to mind when it comes to polyurethane foam. Using this particular sealant, you can fill unnecessary cracks by spraying polyurethane foam, thereby ensuring good thermal insulation. It is this sealant that expands and fills hollow spaces, allowing you to successfully insulate walls, roofs or ceilings.

As a result, you are not afraid of the harshest winters, and comfort in your home is ensured. This sealant was invented by Bayer Otto in the distant 40s of the last century. It was used in industry as insulating boards, then they began to make foam, selling it in aerosol cans. The first country to use this material in construction was Sweden.

This sealant is one of the most beloved by consumers of the different types of similar products currently available. Polyurethane foam allows you to process seams and joints formed after repairs quickly and, most importantly, with high quality. This is the main assistant in any installation work in the fight against drafts.

Top best foams

• Tytan Professional is a moisture-resistant polyurethane foam for professionals. Temperature of use: summer. Available in 750 ml bottles. Poor re-expansion. When applied and further dried, it does not emit toxic substances. Used for installing windows, doors, sealing, insulation, etc. When applied, it does not spoil the surface or deform it. Properties allow it to be used for thermal and sound insulation. Simplicity, precision of application. Compatible with all materials except silicone. Produced in Poland.
• Ceresit WhiteTeq Thermal & Sound is a component mixture for application of white color. Used with a pistol. The temperature of use is from -40 to +90 degrees, therefore it is used for external and internal work. The composition is waterproof. The packaging is convenient and easy to use. Used for sound and heat insulation. Produced in Estonia.
• Makroflex Pro construction foam - a high degree of adhesion to almost all surfaces for a long period, heat and sound insulation qualities, when using a gun, accurate dosage is achieved, saving material consumption. After application, a day must pass for complete hardening. If the temperature during drying is higher than 20 degrees, then the time will be shortened. The material is resistant to temperature changes from -50 to +100 degrees. Application at low temperatures will lead to partial loss of filling properties. Produced in Finland.

Penosil - mounting adhesive foam has plastic properties, which eliminates ruptures after the base dries. Faint odor. Fast setting, high sealing and soundproofing properties. For ease of use and applying an even seam, it is recommended to use a gun. The base contains polyurethane. Requirements for the surface: clean, moistened. Produced in Estonia.

Akfix 805P is a one-component polyurethane mixture. The condition for hardening is humidity. The material is moisture resistant and has high adhesion. Constant direct ultraviolet radiation can shorten the working period of the applied raw material. Use temperature 20 degrees. Before use, shake thoroughly for half a minute. Used with a mounting gun with the bottom up. The plane is cleaned and dust is removed

Foam expands significantly, which is important to consider when foaming. Produced in Turkey.

Hauser sealing foam

Made on the basis of polyurethanes. Produced in several versions: winter, summer, for professional use. Having a low cost, it is an economical type. Does not contain harmful impurities, which is beneficial for the body. Has thermal and sound insulating properties. Produced in Russia.

additional information

An important quality criterion is color. The polyurethane foam should be light yellow. When exposed to sunlight, it turns brown or orange. UV irradiation destroys the structure. The material becomes brittle and loses its properties.

It is necessary to take into account the weather conditions under which the work is carried out. In winter, you need to choose a winter type of composition. This polyurethane foam is designed specifically for cold periods. Its advantage will be a wide temperature range. However, in cases where work needs to be carried out urgently, but there is no winter composition, professionals additionally moisten the working surface to speed up the hardening of the foam.

When working in winter, the cylinder must be heated to 10-20 degrees. This can be done in warm water. But strong heating should not be allowed, because there is a risk of explosion.

Before carrying out repair work, you should read the instructions for each individual composition. To ensure the quality of the material, you need to do testing on a small area. If you have any questions, you can consult a specialist. A responsible approach to work will improve quality and avoid problems.

Polyurethane foam (2 videos)

Polyurethane foam (15 photos)