Polyurethane sealant: pros and cons

Polyurethane sealants are in high demand among modern consumers. They are simply irreplaceable in cases where it is necessary to seal a wide variety of materials with high quality and reliability. It can be wood, metal, brick or concrete. Such compositions are both a sealant and an adhesive at the same time. Let's get to know them better and find out what the pros and cons are inherent in them.

Until the middle of the last century, various joints were sealed with rubber or cork. At that time, these materials were quite expensive and people were looking for more affordable alternatives.

The first experiments on the synthesis of polyamides began in the USA, however, success in this matter was achieved by German scientists who also took part in new developments. This is how the materials popular today - polyurethanes - appeared.

Most buyers opt for polyurethane formulations, since they have many positive qualities.

Let's get acquainted with some of them:

• The polyurethane sealant is highly elastic. It often reaches 100%. It is very easy to work with such a composition.
• Such mixtures boast excellent adhesion to many types of materials. They fit seamlessly on concrete, brick, metal, wood and even glass. In addition, good self-adhesion is inherent in polyurethane-based sealants.
• Such compositions are durable. They are not afraid of high levels of humidity or aggressive UV rays. Not every binding material can boast of such characteristics.

• Polyurethane sealant can be safely chosen also because it perfectly copes with its main task. This building mixture guarantees excellent sealing and waterproofing of the necessary parts for quite a long time.
• Also, temperature drops are not terrible for polyurethane sealants. It easily tolerates exposure to subzero temperatures down to -60 degrees.
• A similar composition can be used at any time of the year. For example, it could be winter with cold ambient air. In such conditions, the sealant will still easily fall on one or another base, so repair work will not have to be postponed to a warmer period.

• The polyurethane sealant does not drip. Of course, this property takes place in cases where the applied layer does not exceed 1 cm in thickness.
• This composition gives minimal shrinkage after polymerization is complete.
• Polyurethane sealant is also convenient because it dries in the shortest time and hardens rather quickly.
• The polyurethane-based sealant can be colored or colorless.

• It is worth noting the environmental friendliness of modern polyurethane sealants. These materials do not contain hazardous and harmful substances released under the influence of high temperatures. Thanks to this advantage, polyurethane sealants can be used without fear in the arrangement of residential premises - baths, kitchens.

• If the air contains moisture, then under its action, such a sealant will polymerize.
• Polyurethane compounds are not susceptible to rust.
• Such materials are not afraid of mechanical damage.

It is worth noting that the polyurethane-based sealant is similar in many characteristics to polyurethane foam during its drying process, since it polymerizes in the shortest possible time and becomes hard.

In the composition of modern sealants there is such a component as polyurethane with a one-component structure. Also in stores you can find two-component options that boast improved sealing properties.

As you can see, such building mixtures have a lot of advantages. However, polyurethane sealants have their own weaknesses.

You should also familiarize yourself with them if you have to work with these materials:

• Although polyurethane sealants have excellent adhesion properties, in some cases they are not enough. A similar problem can be encountered if you seal structures made of certain types of plastics.
• According to experts and manufacturers, polyurethane compounds cannot be laid on substrates with a moisture level exceeding 10%. In this case, they should be "reinforced" with special primers, otherwise you simply will not be able to achieve sufficient adhesion.
• It was indicated above that temperature drops are not terrible for polyurethane compositions. However, it should be borne in mind that prolonged exposure to temperatures of 120 degrees can lead to the fact that the sealant will lose its performance.
• Few people know, but disposal of polymerized sealant is an expensive and very difficult operation.

With a wide range of products, customers can select the best sealant for a variety of conditions. Let us consider in more detail what types of such compositions exist today.

First of all, all polyurethane-based sealants should be divided into one-component and two-component.

Such a sealant is quite common. It is a paste-like substance. It contains one component - a polyurethane prepolymer.

This adhesive sealant boasts increased adhesion in relation to most materials. It can be used even when working with capricious ceramic and glass substrates.

After laying the one-component composition on the joints, the stage of its polymerization begins.

According to experts and craftsmen, one-component sealants are recognized as one of the most convenient to use. To obtain them, you do not need to combine various components, therefore, as a result, the quality of the seams is always excellent. Similar compositions are used both for repair and construction work.

Most often they are chosen for sealing:

• various building structures;
• roof joints;
• car bodies;
• glasses that are installed in cars.

The latter type of sealant is otherwise called glass. As a rule, it is used in the process of gluing car glass, as well as when installing fiberglass decor items in cars. In addition, you cannot do without such a composition if you need to glue glass or plastic elements to a metal base, which is constantly exposed to vibrations, temperature extremes and moisture.

Of course, one-part sealants are not ideal and have their drawbacks. First of all, you should know that you cannot apply them at temperatures below -10 degrees. This is due to the fact that in such conditions the level of air humidity decreases, and after it the polymerization of the material decreases.Because of this, the composition hardens longer, loses its elasticity and loses the necessary hardness. In addition, under such conditions, the one-component adhesive-sealant becomes more viscous, so it becomes very inconvenient to work with it.

In addition to one-component, two-component sealants can be found in stores. In the packaging of such products, there are two necessary components, packaged separately from each other:

• a paste containing polyols;
• hardener.

Until these substances are mixed, they can be stored for a long time, since they do not collide with the external environment.

The main advantage of two-component mixtures is that they can be used even at low temperatures, since during their drying, the moisture present in the air does not take any part in the process.

Using two-component compounds, the seams are also of high quality and very neat.

There are two-component sealants and their disadvantages:

• They can be used only after thorough mixing of the necessary components. This leads to an increase in the time that you have allotted to carry out all the repair work.
• When using a two-component composition, the quality of the seams will directly depend on how correctly the proportions of the necessary components were selected during the mixing process.
• This adhesive must be used immediately after mixing. It won't last long.

If we compare one- and two-component formulations, then we can come to the conclusion that the former are more in demand, since it is much easier to work with them, especially when it comes to domestic use.

As for the construction field, a special sealing adhesive is most often used here for working on concrete. It is distinguished by its composition - it does not contain solvents.

Many consumers choose a sealant designed specifically for concrete as it is fairly easy to work with. In addition, with their use, the seams are of high quality and neat.

Polyurethane concrete sealant is very often used for outdoor work, because it can be applied immediately, without wasting time preparing the composition.

With the help of such a composition, many deformation elements can be eliminated. For example, it can be noticeable cracks and gaps that have appeared in concrete floors over time.

This type of sealant differs in that its composition is based on resin, which is polymerized under special conditions. The result is the same viscous mass that fits seamlessly on many materials.

For roofing, formulations with a suitable density level are ideal. Thus, PU15 is ideal for general roofing work, insulation of coatings, as well as the processing of joints in metal, wood and plastic.

Sealants based on polyurethane differ in that they have excellent strength characteristics and have a long service life. They are not afraid of unfavorable environmental factors. They perform well even under water, so such mixtures can be used in a variety of areas.

Polyurethane sealants adhere seamlessly to most known materials, for example:

• with brickwork;
• natural stone;
• concrete;
• ceramics;
• glass;
• tree.

When open cavities are filled with such a compound, it forms a very neat rubber-like layer. He is absolutely not afraid of negative external factors.It is worth paying attention to the fact that a high-quality polyurethane sealant adheres 100% to certain bases, regardless of their texture.

Once dry, the sealant can be painted over. From this, he will not lose his useful qualities and will not undergo deformation.

Polyurethane sealant is a fairly economical material, especially when compared with different analogues. One package may well be enough to process a large area. For example, if you need to fill a joint that is 11 m long, 5 mm deep and 10 mm wide, you only need 0.5 liters of sealant (or 2 cartridges of 0.3 liters).

As for the average material consumption with a joint width of 10 mm and a depth of 10 mm, it will amount to 1 tube (600 ml) per 6.2 linear meters.

Modern polyurethane sealants are characterized by a short drying time. However, we must not forget that this parameter is influenced by the density of the applied layer.

The polyurethane-based compound adheres seamlessly to other sealants. Due to this property, in the event of damage to the seal, it is easy to repair the affected area. As a result, the improvements will be almost invisible.

Polyurethane sealants are available in clear and colored forms. In stores, you can find not only simple whites, but also gray, black, red, yellow, blue, green and other colorful compositions.

Polyurethane sealants have many positive qualities, including their cost-effectiveness. Many consumers are wondering how to correctly calculate the consumption of such a composition.

The important input data in this case are the width, depth and length of the joint to be sealed. You can calculate how much polyurethane-based sealant you need using the following simple formula: joint width (mm) x joint depth (mm). As a result, you will learn about the need for the material in ml per 1 running meter of the seam.

Modern sealants based on polyurethane are used in various fields, as they are easy to use.

Let us consider in more detail in which cases such adhesives cannot be dispensed with:

• Such adhesives are used for both indoor and outdoor work. It is often used for high-quality sealing of door and window openings.
• Such a sealant can also be used when equipping a new window sill.
• If you need to seal the joints left between the panels, a polyurethane sealant will work best.
• Often, such materials are used when embedding structures made of natural / artificial stone. For this kind of work, a polyurethane-based sealant is ideal.

• You cannot do without such compounds in case you need to process objects that are subject to light vibration, where the filled seams can deform. That is why such products are used in the automotive industry. For example, they can be used to assemble and disassemble headlights and glass.
• Polyurethane-based adhesive sealant can be safely used for high-quality waterproofing of roofs, foundations and artificial reservoirs, since it does not lose its positive qualities in contact with water.
• Often, such sealants are used when assembling various pieces of furniture.

• Polyurethane glue is used for sealing joints and in cases where the structure is under constant temperature fluctuations.
• The suture compound is often used when assembling wooden verandas of various sizes.
• Polyurethane sealant is used for thermal insulation of metal pipes.
• It is also used to prevent corrosion.

In one-component polyurethane-based sealants, only the main component is present. They have no solvent, so they are sold packaged in 600 ml foil tubes.In addition, in stores you can find small containers of 310 ml in metal cartridges.

There are several tools that are used to apply glue.

• Mechanical pistols. Such tools are most often used in private construction, since they can be used to carry out work on a modest scale.
• Pneumatic guns. With such devices, you can perform medium-sized work. Often experienced craftsmen and professional teams turn to such options.
• Rechargeable. Such devices are most often used in the construction of multi-storey buildings.

Before the immediate start of work, a special nozzle is put on the pistol. In order for the quality of the processed seam to be high, its diameter on the sealant itself must be 2 times larger than the depth.

To begin with, from the base that is planned to be processed, it is necessary to remove dust, dirt, paint and any oils.

Seams between blocks or panels are first insulated. For this, foam polyethylene or ordinary polyurethane foam is suitable. The polyurethane sealant must be applied over the insulation layer. For this purpose, experts recommend purchasing hand-held pneumatic guns or spatulas. Spread the mixture evenly so that there are no gaps or voids. After application, the sealant layer must be leveled. For this purpose, jointing made of wood or metal should be used.

3 hours after the completion of all work, the sealant becomes waterproof and resistant to temperature extremes.

Today, there are many manufacturers who produce high-quality and reliable polyurethane-based sealants. Let's take a closer look at some of them.

This manufacturer is one of the largest and most famous. The assortment of the company is very rich. Moment offers not only sealants, but also adhesive tapes, various types of adhesives, chemical anchors, and tile products.

As for polyurethane sealants, among them it is worth highlighting the popular product "Moment Herment", which forms a hard and elastic adhesive seam, which is highly resistant to water, household chemicals, oils, petroleum products, acids and salts.

This popular product is used for insulation and bonding of materials in construction and industry. It adheres easily to wood, skirting boards and various decorative objects.

The Izhora production company is located in St. Petersburg and offers high quality polyurethane-based adhesives to consumers.

Izhora produces both one- and two-component compounds that can be used to seal joints on facades and plinths, when processing seams and cracks on ceilings, as well as for external processing of door and window openings.

In addition, the company offers formulations in gray, blue, green, yellow, brick, pink and lilac colors.

It is a renowned French manufacturer of high quality polyurethane sealants. The brand's assortment includes the popular Isoseal P40 and P25 compounds, which easily adhere to concrete, ceramics, glass, aluminum, steel and wood.

These polyurethane formulations are sold in 600 ml tubes and 300 ml cartridges. Olin polyurethane sealants are also available in a variety of colors: gray, beige, dark beige, dark gray, terracotta, orange, black and teak.

Retel Car is a popular Italian manufacturer of polyurethane joint sealants that are non-drip and perfect for vertical surfaces. They are used in the automotive industry, for sealing containers, for laying air ducts and air conditioning systems.

The Swiss company Sika produces a range of high quality products based on polyurethane. So, Sikaflex sealants are multi-purpose - they are used for roofing work, when installing air conditioning systems, as well as when pouring deformations on concrete.

Also, Sikaflex polyurethane sealants can be used when gluing window sills, steps, skirting boards, and various facing elements. They have excellent adhesion and adhere easily even to plastic.

It is a well-known US brand offering silicone, polymer and polyurethane sealants. The company's products are distinguished by affordable cost and good performance characteristics. For example, the popular composition "Dap Kwik Seal", which is ideal for sealing joints in the kitchen or bathroom, can cost from 177 to 199 rubles (depending on the volume).

If you want to remove the sealant from a particular surface, then you should dissolve it. Special types of solvents for such formulations can be found in many hardware stores.

There is no universal recipe here. Some people use white spirit for this, while others use gasoline.

Roofing compounds cannot be used for interior work, as they are toxic.

Handle polyurethane sealants with glasses and gloves. If necessary, you must also wear a respirator.

If, after applying, you notice that the adhesive layer needs adjustment, then you still have 20 minutes left for this work while it dries.

For information on how to work with polyurethane sealant in a tube, see the next video.