Nanostructured surfaces
Porous surface structure and physicochemical properties of urea-formaldehyde foam
Nemish A.R.1, prof. Kurta S.A.2
1-Member of the circle Ivano-Frankivsk Academy of Sciences "Theoretical and Experimental Chemistry", CNTTUM, Ivano-Frankivsk.
2-Professor of the Department of Chemistry of Vasyl Stefanyk Precarpathian National University ", Ivano-Frankivsk. Ukraine.
  Thermal insulation microstructured foams based on various polymers have been widely used in various industries for thermal insulation of buildings and walls. However, raw materials for the production of most of them are quite expensive. In this regard, the urgent problem is the production of foams based on cheap and technological polymers, which are urea-formaldehyde resins (UFR).
   Urea-formaldehyde foams of the UFR type occupy a special place among gas-filled plastics for thermal and sound insulation. The inability of UFR to self-combustion, and to stop combustion after removal of the flame source and the inability to melt the UFR polymer during combustion indicates a high fire safety of urea foam compared to polystyrene and polyurethane foam. Their main advantages are good thermophysical characteristics, but low manufacturability and high flammability of polystyrene foam and polyurethane foam. Urea-formaldehyde foams are almost as good as polystyrene and polyurethane foam in terms of industrial production of thermal insulation. But UFRs have a number of disadvantages, namely, emit large amounts of toxic formaldehyde in their manufacture and molding. In addition, UFRs have a large shrinkage after curing, which reduces by 15-20% the linear and volumetric dimensions of the foam after curing. Industrial brands UFR have high water and moisture absorption, which leads to a deterioration of the thermal insulation properties of urea-formaldehyde foam, so they must be protected during long-term operation.
  For the production of foams use mainly urea-formaldehyde resin with a reduced content of free formaldehyde (0.1-0.05%). However, during the formation, application and curing of UFR foam, an additional amount of gaseous formaldehyde is released, which can reach the maximum allowable concentration = 0.5 mg / m3 in the working area of ​​insulation.
  Therefore, in this work, an attempt was made to reduce the emission of free formaldehyde from UFR through the introduction of chemical formaldehyde acceptors in UFR composite polymer mixture for foaming. Additionally, the linear shrinkage was reduced to 3-5%, and the water and moisture absorption of foamed UFR was reduced to a minimum.
  A positive result was obtained due to the introduction of special chemical acceptors of formaldehyde and chemical foaming agents. This led to a 2-3-fold reduction in the emission and concentration of free formaldehyde from urea-formaldehyde foam and a reduction in its volume shrinkage, and a decrease in water and moisture absorption of UFR. New chemical formaldehyde acceptors have been proposed that can rapidly and efficiently interact with free and bound formaldehyde in urea-formaldehyde foams during manufacture and operation. A new method for determining the emission of gaseous formaldehyde from urea-formaldehyde foams has been developed, which is based on the use of the MIS-98170 formaldehyde gas analyzer as the main component of the developed installation. Due to the use of special new chemical gas-forming foamers, the linear and volume shrinkage of UFR was reduced by 3-4 times, to the above values.
 Additionally, new film-forming substances have been proposed as protective coatings for urea-formaldehyde foams, which has significantly reduced their water and moisture absorption and improved their thermal insulation properties. The proposed new method for determining the emission of formaldehyde gas analyzer MIS-98170 for urea-formaldehyde resins and foamed materials can be used in the production and formation of insulating layers of foam on the surface and in the industrial production of particle board (chipboard) for furniture and construction.. 

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