Geopolymer foams obtained by the saponification/peroxide/gelcasting combined route using different soap foam precursors

This work investigates the influence of eight different vegetable and animal sources of fatty acids as soap foam precursors in the processing of highly porous geopolymers. Four sources rich in saturated chains ( coconut and babassu oils, palm stearin and beef tallow), two sources rich in monounsaturated chains ( olive and castor oils) and two sources rich in polyunsaturated chains ( sunflower oil and soybean biodiesel) were selected. For all soap precursors, bodies treated at 300 degrees C possessed a very high total porosity (84-88 vol%), open porosity (79-85 vol%) and relatively high specific surface area (35.1-63.5 m(2)/g), but rather low compressive strength (0.2-0.4 MPa). The increase in the thermal treatment temperature caused a slight decrease in porosity but a substantial increase in compressive strength and decrease in specific surface area due to sintering and formation of crystalline phases. The Darcian permeability coefficients of all bodies (0.6-10.6x10(-10) m(2)) were typical of gelcasted foams, aerosol filters and fibrous mats. The morphology of pores could be well-associated to the features of lathers produced by the respective soap precursors.