Foaming of CRT panel glass powder using Na2CO3

The recycling of glass from obsolete cathode ray tubes (CRT) has hitherto only occurred to a very limited extent, but the production of foam glass used as an insulation material component has recently been proposed as a promising recycling method. CRT panel glass has high recycling potential due to its non-hazardous composition. Here we report on the foaming of CRT panel glass using Na₂CO₃ as the foaming agent. We explore how heat treatment temperature and concentration of Na₂CO₃ affect the density and porosity of the foam glasses, and whether Na₂O is incorporated in the glass network. The optimum foaming temperature for minimising density and maximising closed porosity is found to be between 1023 and 1123 K. The pore structure depends on the amount of added Na₂CO₃, viz, the pores generally become more open with increasing Na₂CO₃ content. A minimum density of 0·28 g/cm³ is found when 14 wt% Na₂CO₃ is added and the heat treatment temperature is 1023 K. Interestingly, the glass transition temperature (T_g) of the final foam glass decreases linearly with increasing [Na₂CO₃], indicating that the Na₂O is incorporated into the glass network.