Sintering Behavior of Expanded Perlite Thermal Insulation Board: Modeling and Experiments

A finite difference-based mathematical model for sintering behavior prediction was developed with determination of corresponding sintering kinetics for a new type of expanded perlite-based insulation board. The insulation board was developed in cooperation between the company Trimo, d. d., and the Faculty of Chemistry and Chemical Technology of the University of Ljubljana. The board was produced by mixing expanded perlite with prescribed particle size and sodium silicate solution, molding and pressing the mixture and drying the so-formed board in a microwave cavity, followed by a high-temperature thermal treatment of the dried board. During the high-temperature thermal treatment of the board, certain shrinkage appeared, a result of a sintering process inside the board. A certain amount of shrinkage is needed for a board to obtain sufficient mechanical properties and to increase the durability of the insulation board in moistened conditions. During this process, the mathematical prediction of the sintering behavior is the key to achieve the right balance between the low final density, which is the basis for good thermal insulation properties, and good mechanical properties and durability, achieved only by allowing the material to reach the right sintering temperature.