Microwave technology of thermal insulation materials based on liquid glass as an alternative to foam glass

Abstract

An energy-saving and environmentally friendly microwave technology is proposed for producing composite thermal insulation materials based on liquid glass, which are not inferior to foam glass in terms of their properties. It is shown that the use of microwave radiation allows fabricating volumetrically grouted materials by simultaneous porization of the granules and the binder. In such a way, a monolithic structure of products is formed, where the space between the granules is filled with the swollen binder limited by a denser surface layer. It has been proven that the use of microwave radiation allows achieving heating and softening of the entire mass of the liquid-glass composition due to the internal acceleration of the movement of water molecules, their friction, and release of thermal energy, and not due to high temperature from the outside. This has made it possible to carry out swelling at a lower temperature and during a much shorter heat treatment time than at the traditional convective heating, because the sample layer is heated almost instantly under microwave exposure and the liquid glass composition reaches a pyroplastic state in a few seconds. It has been determined that a part of the energy of electromagnetic radiation is transformed into heat, which contributes to intensive porization with the volumetric expansion of the liquid-glass composition. The other part of the energy is directed to structural changes in the material leading to the improvement of its properties, which is associated with the "non-thermal" microwave radiation action.