Study On The Composition,Structure And Properties Of Borosilicate Fire-resistance Glass

Fire-resistance glass with many excellent properties,such as high transmittance,heat insulation and flame retardance has been widely used in different kinds of modern buildings,which can block the heat radiation and spread of smoke and fire.Borosilicate glass has a low coefficient of thermal expansion,high softening point,excellent corrosion resistance and mechanical properties,which is a promising material in the field of monolithic fire-resistance glass.Because of the high melting temperature,serious volatilization of boron,phases separation and other issues,it is difficult to achieve large-scale continuous production for borosilicate glass by float process at the present.In this paper,the volatilization of boron and melting temperature of borosilicate glass were investigated.In order to select the suitable raw materials,boron oxide in the base glass was introduced by different raw materials,and the volatilization of boron and melting temperature were estimated.The effect of the glass batches feeding temperature on the boron volatilization was also studied.The influence of the B₂O₃/SiO₂,Al₂O₃/SiO₂,K₂O/Na₂O and CaO/SiO₂ ratios on the structure and properties of glasses was investigated.According to the characteristics of the floating process,the effects of composition changes on melting and forming temperatures were investigated by the viscosity and thermal expansion tests.Finally,flexural strength and chemical stability of the glass samples were tested.In this paper,the ranges of composition proportion were that:B₂O₃/SiO₂:0.080-0.128;Al₂O_3/SiO₂:0.010-.041;CaO/SiO₂:0-0.056;K₂O/Na₂O:0-1.59.The results show that:?1?The anhydrous borax was the suitable raw materials to introduce boron oxide,which can decrease the volatilization of boron and high temperature viscosity efficiently.With anhydrous borax as the raw material,the volatilization rate of boron oxide was less than 0.3%when the feeding temperature was 1450???2?With the increase of the ratios of B2O3/SiO2 and Al2O3/SiO2,the content of[BO₃]units increased,and the aggregation degree of the glass network structure decreased.The coefficient of thermal expansion increased with the increase of B₂O₃/SiO₂?Al₂O₃/SiO₂?CaO/SiO₂ and K₂O/Na₂O ratios.The glass transition temperature Tg and thermal expansion softening temperature Td decreased with the increase of the ratios of B₂O₃/SiO₂ and Al₂O₃/SiO₂,while they increased with the increase of the ratios of CaO/SiO₂ and K₂O/Na₂O.?3?With the increase of the ratio of B₂O₃/SiO₂,glass viscosity,melting temperature Tm,temperature point in the tin bath Tt and softening point Ts decreased.With the increase of the ratio of Al₂O₃/SiO₂,the high temperature viscosity increased while the low temperature viscosity decreased.The T_m and T_t increased,at the same time,T_s decreased slightly.With the increase of the ratio of CaO/SiO₂,high temperature viscosity decreased while low temperature viscosity increased.T_m and T_t decreased,while Ts slightly increased.With the increase of the ratio of K2O/Na2O,glass viscosity,T_m?T_t and T_s all increased.?4?The variation trends between the workability of the glass of melting and clarification stage and tin bath forming stage are different.In the melting and clarification stage,the workability of the glass became shorter with the increase of the ratios of CaO/SiO₂ and K₂O/Na₂O,and became longer with the increase of the ratio of B₂O₃/SiO₂.With the increase of the ratio of Al₂O₃/SiO₂,the workability of the glass became shorter firstly and then became longer,which reached the shortest when the content of Al2O3 was 2.0 mol%.In tin bath forming stage,the workability of the glass became shorter with the increase of the ratios of B₂O₃/SiO₂ and CaO/SiO₂,while the workability of the glass became longer with the increase of the ratios of Al₂O₃/SiO₂ and K₂O/Na₂O.?5?The fragility index m of glass decreased with the increase of Al₂O₃/SiO₂ ratio,and increased with the increase of CaO/SiO₂ ratio.There was an inverse correlation between the workability and fragility index m.The changes of B₂O₃ and K₂O content had little influence on fragility of the glasses.