Among the insulating materials commonly used in the construction of buildings, rigid foams of projected polyurethane stand out.
This type of material is manufactured on site on site as a result of the combination of two liquid components at room temperature, polyol and isocyanate. The union of both components generates an exothermic chemical reaction as a result of the formation of bonds between both components. The product obtained has a cellular structure and rigid consistency. It is the so-called rigid pur polyurethane foam.
Closed-cell PUR microscopic view
Among its features are:
Low density of the order of 35 kg/m3, due to its cross-linked structure with a high amount of air inside.
Low thermal conductivity, of the order of 0.028 W/(m K).
Waterproof to water.
It allows the diffusion of water vapor.
Due to these characteristics it is a material used in applications in which the flow of heat through enclosures, whether exterior or interior, wants to be reduced.
Two modes of manufacture/application on site are distinguished:
Application by projection, spraying the two components simultaneously on the surface that serves as their substrate. Application by injection or casting, both components are mixed by shake and introduced into a cavity where their expansion occurs.
These application techniques together with their excellent adhesion properties on almost any substrate make their application comfortable and fast, favoring the continuity and absence of joints that could decrease their effectiveness.
It is a material resistant to aging due to its microscopic structure that prevents the entry into its interior of water or dirt that could degrade it.
There are multiple constructive solutions in roofs, facades and interior enclosures that apply the PUR, either in the construction phase or in the rehabilitation of buildings.
In future posts we will develop some of these solutions that reduce the energy demand of buildings and CO2 emissions into the atmosphere.
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