Foaming mechanism and optimal process conditions of foamed glass based on thermal analysis

The properties of foamed glass are substantially determined by interaction between glass and foaming agent during sintering process. Knowing the foaming mechanism and the influence of process conditions will help to reduce the defects of foamed glass. In this research, the TG–DSC–DTG thermal analysis was used to investigate the thermal behavior of waste glass, graphite (foaming agent) and their mixture to explore the foaming mechanism, as well as the effect of process conditions on the properties of foamed glass was discussed. Results indicate four stages in the weight-loss can be distinguished during the heating process: (I) 25–300 °C, (II) 300–450 °C, (III) 450–748 °C and (IV) above 748 °C. The (IV) stage between 748 and 909 °C is the main stage of foaming. Foaming temperature, holding time, foaming agent content and milling time have difference effects on the properties of foamed glass. Foaming temperature and holding time mainly affect the distribution of pores and average aperture respectively. The thickness of the pore wall and density of the foam are determined by foaming agent content, while milling time can control the quality of foamed glass by affecting the particle size of the mixture. The foamed glass showed the best properties when the mixture with 2 wt% foaming agent was sintered at 880 °C for 10 min after milling for 2.5 h.