Applications of Polyurethanes in Construction Material as Adhesive

Polyurethanes are the solution to the need for special materials under construction. The polyurethane products and the corresponding technologies allow an economic manufacture and the realization of new ideas.

Construction systems progress and the needs to conserve energy increase, and the rigid polyurethane foam may be the optimal product to reach these goals. They provide the most efficient insulation available to the construction and refrigeration industry. Polyurethane readily combines with the available surface finishing materials, offering the possibility of producing different compounds. From refrigeration chambers to energy generators, where any possibility of condensation of water in the roof must be eliminated, are some examples. In the heating and cooling technology, polyurethanes are used to isolate pipes and in case of large areas need to be insulated, the polyurethane spray application method is used. The rigid foam can be obtained in the form of insulation plates for ceilings and walls, and it can be injected to fill the cavities, in the construction of boats, etc. Where a low conductivity, high strength and low weight insulation are required, a rigid polyurethane foam may be used.

Unlike rigid foam, the flexible polyurethane foam has an open cellular structure, and it is a very elastic material, which when removed the load to which it has been subjected, instantly recovers its original shape. It is a very light material and with a high permeability to the air, choosing the raw materials in its manufacture and varying the formulation, and we can regulate its properties as the cushioning, the elastic characteristic, the cellular structure, the bulk density and the hardness. The important fields of application are found in the industries of car seats, chairs and mattresses, and they are also applied for packaging delicate equipment in hospital articles, etc.

Polyurethanes are formed by a mechanism in which water reacts, in most cases, with a formulated additive containing isocyanate groups. As in the case of silicone, the water molecule has to migrate into the adhesive where the bond occurs. Its curing behavior is therefore the same as that of silicones, but without releasing by-products into the environment. The rate of curing also depends on the relative humidity, as in the case of silicone.

To achieve the best and most durable adhesion, the use of appropriate cleaning and priming products is recommended. Different primers are used depending on the substrates. The application of polyurethane foam by spray not only provides excellent thermal insulation and antifogging but also perfect waterproofing. This is because 90% of the cells are closed and act as a continuous barrier to water penetration. Whereas in the conventional flat roofs, it is necessary to install a large number of layers by superposition with different functions for each in the coating by projection, in principle, only one material, which by its mechanical resistance and its adhesion over the whole surface, improves the structural rigidity of all types of roof. This system is particularly important for the renovation of thermo-hydrophobic protection of deteriorated roofs and for new concrete or sheet buildings.

 

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