Caracterização de espuma rígida de poliuretano aplicada em refrigeração

Abstract

Polyurethanes are a class of polymeric materials, which presents great versatility and variety of applications, has being shown in this work as rigid foam. One of the main applications of this material is in refrigeration, since it has good capacity of thermal insulation and in molding sandwich structure. However, there is a recurring problem in this application which is the refrigerators walls deflection formation due to the so-called bimetallic effect. The object of the present work arose from being in touch with an industry of this field in the city of Londrina that passed through hard problems with this phenomenon. There were doubts about the quality of the polyurethane system used. With this, the foam analysis was performed through the determination of the apparent density, compression and bending mechanical tests, chemical composition analysis by infrared spectrometry and morphological analysis by scanning electron microscopy. The results showed that the foam has sufficient mechanical strength for the application, composition uniformity and adequate cell size. However, it was possible to notice oscillations along the material, demonstrating that anisotropy of the cellular structures could occur. An analysis of the reaction times was made based on data provided by the company to evaluate the reactivity of the system. From this analysis, the influence of temperature and the need to control this parameter in processing were noted. Finally, theoretical analysis was made regarding the thermal conductivity of the system and proposals to reduce the effects of the deflections in the cabinets.