a rigid foam plastic produced from urea-formalde-hyde resin.
Mipora is produced by mechanical beating of an aqueous emulsion of the resin modified by glycerol to reduce brittleness. The operation is performed in apparatus with a multipaddle mixer. Petroleum sulfonic acids are used as the foaming agent, and organic acids are used as hardening catalysts. The foam produced is poured into metal forms in which hardening takes place, first at room temperature and then in drying chambers at 30°–50°C. The finished product is in the form of blocks, plates, or chips. In other techniques, the foam is poured directly into a mold, in which it hardens at room temperature.
Mipora is almost ten times lighter than cork (apparent density, not more than 20 kg/m3). Its coefficient of thermal conductivity is 0.03 watt per (m-°K), or 0.026 kilocalorie per (m-hr-°C). It chars but does not burn in an open flame at 500°C. With the addition of flame retardants, it does not ignite in an oxygen atmosphere. Mipora has considerable water-absorption capacity and is sensitive to aggressive chemical reagents. It is protected in storage and use by a cellophane or polyethylene film.
Mipora is used as a thermal and acoustic insulation material in construction and in the production of refrigerators and of storerooms and vessels for transporting liquid oxygen, as a filler for hollow structures in automobile and truck production, and for improving the structure of soils.