Polyurethane sealants: properties and applications

Polyurethane sealants: properties and applications

Polyurethane sealants are in high demand in many industries. The mixtures are of high quality, reliable adhesion and long service life. The properties and use of this sealant make it the best choice for working joints on a variety of surfaces..

What it is?

Polyurethane-based sealant belongs to the category of viscous polymer elements, the production of which is carried out using elastomers of synthetic origin. Polyurethane sealants are considered a new technology. They can guarantee a high-quality and reliable level of waterproofing of joints and cope with the most vulnerable spots on the roof..

The material is often used to interact with abutments on roofs, valleys, single sheets and other components that relate to anchorage points.

Until the middle of the last century, cork or rubber was used to ensure the tightness of various types of joints, as well as to seal the seams.. They were considered expensive materials that were difficult to replace. Engineers could not find a similar adhesive that could be produced in unlimited circulation using available and inexhaustible resources..

The United States was the first state to experiment with the synthesis of polyamides. However, German scientists were able to cope with the task. They created a polyurethane elastomer by combining polyols with certain diisocyanates. As a result of their experiments, polyurethanes were obtained, which are known throughout the world..

Properties and characteristics

Polyurethane sealants are often used for bonding brick, metal, concrete and plastic products. During application, the product acts as a sealant and adhesive. When the polyurethane hardens, the elements adhere well to each other. Polyurethane is resistant to moisture, corrosion and vibration. High humidity levels have an effect on improving the properties of polyurethane.

The composition of the sealant forms one main substance, which is polyurethane, the structure of which contains one component. But there are also products made of polyurethane, the structure of which is formed by two components. They are characterized by improved sealing qualities. The elasticity index is 99.9%. If we compare the material with construction foam, the technical qualities of both substances will be the same..

Polyurethane sealants are similar to foam for installation during polymerization, since the substance hardens and takes on a solid form a couple of seconds after being placed on the surface. The presence of a large amount of moisture allows the mixture to polymerize.

During use, it should be borne in mind that the sealant quickly hardens, so it should be applied carefully.

Store the sealant in a cool place. If normal conditions are provided, the mixture can be stored in an open tube for about 10 months. The sale of the product is carried out in tubes, the weight of which is 600 ml, 750 ml, in buckets, metal cartridges. When buying, you should make sure that the product has a certificate of conformity.

Positive qualities of polyurethane sealant:

  • maximum elasticity index;
  • high-quality level of adhesion in relation to surfaces made of metal, brick, concrete, plastic, ceramics;
  • high degree of self-adhesion;
  • operational polymerization;
  • moisture resistance;
  • the sealant can be used at a temperature of -50 degrees;
  • Shore A hardness is 15-50 units;
  • high tensile strength;

  • vibration resistance;
  • resistance to chemicals;
  • the material can be painted;
  • the density of the sealant is 1200-1500 kg / cu. meter;
  • resistance to UV rays;
  • the material does not shrink;
  • the product contains no toxic components;
  • long service life.

Among the negative qualities, one can note their instability to temperatures above 100 degrees..

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Polyurethane sealants are classified into two categories: one component based and two component based

One component polyurethane sealant

Such products are among the materials in the form of a paste. The main component is polyurethane-type formopolymer. Such adhesives are characterized by increased adhesion to various building materials. It exhibits good adhesion to glass and ceramic surfaces. After the one-component sealant is applied to the surface, it begins to solidify due to contact with moisture in the air..

One-component products are easy to use, since this suture does not require mixing of components. For this reason, the seams will be of high quality..

Sealants are actively used during repair and construction, as well as to ensure the tightness of the following elements:

  • various structures in construction;
  • roof joints;
  • vehicle body;
  • for glass in a car.

    Often polyurethane sealants are called glass sealants, as they are in demand when gluing car glass, during the installation of fiberglass decorative parts. One-component compositions are suitable for glass with metal. Due to the fact that the material is waterproof, the area of ​​its use increases.

    The product can be used on substrates that are exposed to high temperature conditions and vibrations. Ease of use lies in the fact that the sealants foaming for the dispensers are located in a convenient tube. Foam adhesive quickly applies to different joints and hardens.

    High modulus polyurethane based sealant with high quality is in demand.

    One-component sealants have one drawback, which is that they cannot be used in the winter season when the thermometer drops below 10 degrees..

    This is due to several factors.

    • By lowering the temperature regime, a decrease in the level of humidity is observed. This leads to the fact that the rate of polymerization of the agent is significantly reduced..
    • Due to the increased cure time, the liquid sealant will lose its elastic properties along with adhesion and hardness..
    • At a negative temperature, the viscosity of the mixture increases, so the use of a sealant is difficult.

    Two-component sealants

    The packaging with such a product contains two elements that are in separate packages:

    • paste with polyols;
    • hardener.

    Until the ingredients are mixed, they can be stored for a long time, as they do not come into contact with the environment..

      The main advantage of two-component products is that they do not lose their properties at negative temperatures.. This is due to the fact that during polymerization, they do not need the moisture contained in the air. The composition of the mixture provides a strong, elastic and durable seam.

      Among the disadvantages are the following qualities:

      • additional time is required for mixing components, which leads to an increase in the term of work;
      • the quality of the seams depends on the correct choice of the proportions of the ingredients during mixing;
      • the resulting adhesive mixture should be used immediately after mixing.

      If we compare mixtures with two components with sealants, the structure of which consists of one substance, we can conclude that for domestic use it is best to purchase sealants based on one component.

      In construction, specialty polyurethane sealants are commonly used that are aimed at working with concrete surfaces. The peculiarity of such products is that there are no solvents in the composition. The wide demand is due to the convenient operation and high quality seams that are formed after the application of the hermetically sealed mixture.

      If you need to get rid of various kinds of cracks and gaps that appeared during the construction of a house, a polyurethane mixture provides high quality waterproofing.

      Consumption

      Polyurethane sealant is economical in consumption. For example, if you need to process a seam with a depth of 10 mm, you need to use about 100 ml of the product for 1 m of this seam..

      Colour

      The color solution of the sealants may vary. Some users opt for a transparent sealant that is invisible on surfaces. However, there is a colored material on sale that is suitable for surfaces of different colors. Black, gray, white and even brown sealants are common. They do not stand out from the general color scheme of the treated surface and do not spoil the appearance of the object..

      A colorless sealant is considered the best choice for glass applications. It is invisible on products and ensures invisibility of the seam.

      Application

      Polyurethane-based sealants are renowned for their many positive qualities, so their field of application is diverse. Such material is able to cope with interpanel joints and ensure the proper quality of expansion joints. The products can provide proper quality tightness for the roof, are used for joints on logs and glass units.

      Polyurethane sealants can be used as an adhesive, which effectively handles joints in concrete surfaces as well as interacts with joints present between reinforced concrete slabs.

      When choosing mixtures for working in a domestic environment, it is recommended to remember its main quality, which is hardness. Due to it, the product resists deformation effects and shrinkage..

      If the degree of hardness of the selected mixture reaches 15 units, it is allowed to choose it to eliminate the seams that are located between the panel material, as well as to process corners and joints of a different nature. Polyurethane mixtures are optimal for wood, sealing joints in timber, joining various plastic parts.

      With a hardness index of 25 units, the sealant is relevant for interacting with joints, which are often affected by moisture. Such products are often used for bathrooms, gearboxes, roofing and other surfaces..

      The hardness of 40 units makes it possible to operate the mixture as a glass sealant. But it can also be used for concrete floors. The material is able to cope with the sealing of expansion joints, which are present in reinforced concrete structures.

      Polyurethane sealants, which have a hardness index of up to 50 units, can be used for metal work. The highest hardness index reaches 60 units. Similar products are used for bodywork and shipbuilding..

      Sealants of this type are in demand in various industries..

      • Working with window and door structures, processing interpanel joints on the facade of the building. When the package with the mixture is open, the mixture must be used immediately. It should be applied to the seam itself, observing the application thickness, the maximum size of which is 0.5 cm.Thanks to this approach, you can obtain a tight connection and save on consumables.
      • Polyurethane sealants are often used on natural stone products. Due to such mixtures, a seam that is almost invisible to the human eye can be obtained. The products are available in various colors, so you can choose a shade that is as close as possible to the color of the surface. Silicone sealants are not suitable for working with stone, as they negatively affect the color and structure of the stone. Polyurethane mixtures are the best solution for this case..

      • For areas subject to increased vibration, a polyurethane based sealant should be used. The choice is based on resistance to deformation and shrinkage. The mixture is used in the automotive industry, when working with seams on metal surfaces. The material provides quick drying and the required level of strength.
      • And also such mixtures are used to work with seams that are affected by high or low temperature conditions. High demand due to good elasticity, puncture, destructive and abrasion resistance.
      • Polyurethane mixture is the best roofing sealant. And also it can be used to eliminate seams when arranging a reservoir or fountain. After processing, polyurethane is characterized by a high level of strength along with resistance to moisture.

      Manufacturers

      Polyurethane-based sealants are produced by many brands, among which three manufacturers are in demand.

      Buyers highlight the company “Rastro”, which has been producing building materials for 20 years. Brand specialization: production of materials for construction, renovation works, waterproofing. An enterprise was founded in St. Petersburg, and at the moment the company has branches and warehouses in different cities on the territory of the Russian Federation.

      During the manufacture of products, the manufacturer uses only high quality materials, along with the use of new technologies. For this reason, most of the buyers choose this particular brand..

      “Rastro” produces a sealant based on polyurethane Izhora. The mixture belongs to the category of two-component and is distinguished by reliable sealing of seams, cracks at the joints and the front part. The product is characterized by a high level of elasticity and reliable adhesion to the base. The production is carried out in white and gray colors, however, when ordering, you can specify the desired shade and get the required option.

      Polyurethane sealant is widely used “Sazilast”. Under this trade brand, a whole line of mixtures consisting of one or two components are produced, which are used in various industries..

      “Sazilast” can be used in adverse conditions, which include temperature extremes, constant humidity and exposure to chemicals. Sealants can be used for outdoor work (when repairing the facade, roof), as well as for working with foundations and roads. The certificate of conformity guarantees high quality products.

      Moment sealants are produced by the Herment company. The manufacturer is engaged in the production of not only polyurethane mixtures, but also other types of sealants. This brand is in great demand among consumers, as the manufacturer pays attention to the high quality of products, being engaged in quality control.

      Moment is characterized by a long service life, resistance to chemicals and other adverse factors. But also the mixtures demonstrate high elasticity, have good adhesion to different surfaces. The manufacturer provides a quality certificate for its products.

      Application instructions

      Since the constituent part of the raw material is due to the use of only one main component, and there are no different kinds of solvents in its structure, the release of the sealant is carried out in foil tubes, metal cartridges and in buckets. The mixture is applied using special tools called pistols.

      There are three types of spray guns on sale.

      • Mechanical pistols. They are made for private construction work, as they can only cope with a small amount of tasks..
      • Pneumatic guns. The tool is aimed at medium-sized jobs and is often purchased by professional builders.
      • The gun is equipped with a rechargeable battery. Such a tool is used in the construction of high-rise buildings..

      Before work, you need to put on a special nozzle on the selected gun, cut the seam to the desired length. In order for the sealant to bond the surfaces efficiently, care should be taken that the size of the diameter on the mixture is twice the depth of the seam itself, on which the mixture will be applied..

      Before using the sealant, you will need to carry out preparatory measures: you need to remove all dust deposits, paint and various oil materials from the treated surface. Masters advise against using the sealant outdoors, when it is raining outside and during other atmospheric precipitation. If there is rust on the base, it must be removed with a grinder or sandpaper. Thanks to such actions, it is possible to increase the adhesion rates several times..

      Interpanel or interblock seams must be insulated in advance. The action can be performed using construction foam for installation or use polyethylene foam. It is recommended to apply the sealant over the insulation material. To do this, you need to use hand-operated pneumatic guns or spatulas. The mixture should be spread over the surface in a measured manner. No voids or breaks allowed.

      To level the applied material, you will need steel or timber joining. The base should take on an L-shape. The sealant dries quite quickly, but three hours after application it turns into a mixture that is resistant to negative temperatures, moisture, and the influence of atmospheric precipitation. Until this moment, the sealant should not be exposed to such irritants..

      Than to dissolve and dilute?

      Not every user can gently apply polyurethane-based sealant to seams or joints. Since the product cures very quickly, many people are looking for information on how to scrub the polyurethane-based sealant and soften the mixture..

      One-component and two-component mixtures can be removed with alkaline materials. However, it should be borne in mind that you should start cleansing immediately. Otherwise, it will not work to remove excess particles of matter..

      Some manufacturers make special preparations for removing polyurethane sealants. AcesolvePUN is in demand. It has proven itself well in cleaning the mixer (special mixing machine), hoses and gun. The product is able to cope with uncured parts of the sealant.

      Cured sealant will not be removed. Using solvents will cause the mixture to swell.

      For more information on the use of polyurethane sealants, see the next video..

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