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- ItemAngular emissivity at room temperature and spectral reflectance at near normal incidence of float glass, borosilicate glass and glass-ceramics(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1996) Lohrengel, Joachim; Rasper, Manfred; Geotti-Bianchini, Franco; De Rio, LucaAn accurate investigation of the emissivity of uncoated flat glass (necessary to calculate the solar factor and the U value of glazing according to standardized procedures) was performed in agreement with Groupement Europeen des Producteurs de Verre Fiat, in support of CEN and ISO standardization activities. The total angular emissivity of a range of uncoated float glass samples was determined between 10 and 80 °C with an uncertainty of 0.5%. Both the normal and the hemispherical emissivity were nearly identical for all the samples investigated. No significant differences between the top and the bottom side were observed. Measurements were also extended to borosilicate glass and glass-ceramic plates used for fire-resistant glazing, determining their thermal conductivity and angular emissivity behaviour. In order to obtain addidonal information, also the spectral reflectance curves at near normal incidence between 2000 and 200 c m ⁻¹ were obtained using a spectroradiometer. The fact that almost identical curves were obtained for a wide range of float glasses (both sides) as well as for the fire-resistant materials confirms the correctness of the close emissivity values found. On the basis of the resuhs obtained, a Standard value of εn = 0.900 and a εh/εn ratio = 0.936 is suggested for both float glass and for the two other materials.
- ItemInfrared spectroscopic analysis of water incorporated in the structure of industrial soda-lime-silica glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1995) Geotti-Bianchini, Franco; De Riu, LucaThe paper illustrates a method for the determination of the water content of glasses by infrared transmittance spectroscopy from the exdnctions of the bands due to free and hydrogen-bonded hydroxyl groups dissolved in the glass. The procedure is discussed in detail, highlighting the sources of random and systematic errors and what can be done to improve the interlaboratory reproducibihty. The ratio of the intensities of the two bands at 2.8 and 3.6 µm is investigated accurately for a range of industrial soda-lime-silica glasses. In the case of containers and float glass it is nearly constant, but it varies widely for other products, such as household appliances, car headlamps and hand worked arücles, probably due to differences in the glass formulation. Accordingly, caution should be exerted in using the simplified method based on the measurement of the first band only, implying a constant rado. Finally, evidence of molecular water in the dealkalized surface layers of commercial articles is obtained using infrared reflectance spectroscopy.
- ItemWater content of sulfate-fined industrial soda-lime glass and its influence on workability(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1998) Geotti-Bianchini, Franco; De Riu, LucaThe aims of the paper are: a) to systematically determine by IR spectroscopy the water content of sulfate-fmed industrial soda-lime glass (mainly Container and float, besides that household and technical glass) produced in Italy; b) to highlight the influence of redox State , melting conditions, batch and cullet addition on the water content; c) to check the consistency with time and between different feeders of the water content in the glass produced by a given furnace; d) to assess possible correlations between water content and workability in Container glass. The water content ranges between 300 and 400 ppm in conventionally fired glass, with electrical melting it decreases to 150 to 200 ppm, with oxycombustion it increases to 500 to 600 ppm. In the case of conventional flame melting the main factor influencing the water content is the redox State , due to a water/sulfate exchange. When a glass with a given color and redox State is produced in a given furnace, the daily oscillations of the OH level are moderate, with negligible effects on viscosity. In all the workability problems analyzed the contribution of water content oscillations was negligible as compared to other factors. According to the results obtained, significant water-related viscosity variations are expected to take place only when the meldng atmosphere or the redox conditions are significantly altered.
- ItemStudy of the high-temperature spectral behavior of container glass(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1997) Endrýs, Jiří; Geotti-Bianchini, Franco; De Riu, LucaThe spectral absorption coefficients of container glasses in the wavelength region from 0.4 to 4.5 µm and in the temperature range from room temperature to 1400 °C were measured by a single-beam spectrophotometer by means of the transmission method. From the measured absorption coefficients radiative thermal conductivities in the temperature ränge from 600 to 1400 °C were calculated by means of Rosseland's diffusion approximation. The intensity of the band at 2.8 µm due to dissolved hydroxyl groups in glass was also calculated. While most previous measurements were performed on model glasses with a very simple basic composition, molten in laboratory furnaces from pure raw materials, the glasses investigated in this paper are the most frequently used types of container glasses with a complex composition and different chromophores. The influence of different coloring agents and dissolved water on the spectral behavior and radiative thermal conductivity of glass were studied, checking how the spectra change from room temperature to high temperature.
- ItemAnalysis of polyethylene-based cold end coatings on glass : Containers with contact angle and IR spectroscopy(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1999) Geotti-Bianchini, Franco; Preo, MartinaThe aim of cold end coating is to protect the glass surface from abrasive wear with the help of a suitably anchored film of organic material which decreases friction, by preventing direct glass to glass contacts. At present, routine controls on cold end coatings are limited to a lubricity test, i.e. the determination of the slide angle. Α laboratory procedure based on the determination of the contact angle with water is described in this work. It allows one to estimate the coverage with cold end coating locally from the waterrepellence caused by the organic deposit. This method can be used to investigate a ränge of problems associated with glass wettability, including label adhesion, acid etching and washing residues. The contact angle correlates well with the slide angle. Qualitative information on the nature of cold end coatings is obtained by extracting the glass with volatile organic solvents such as methylene chloride, evaporating them and analyzing the residue with infrared spectroscopy. In the case of a coating with RP 40 LT the IR curves show the presence of Polyethylene partially oxidized in order to improve adhesion to the glass surface, besides Polyethylene glycol added as an emulsifying agent. If the cold end coated container is rinsed with water, the glycol dissolves, but the Polyethylene derivative remains strongly anchored. Such bond withstands even drastic washings with water and detergents, alkali or oxidizing acids. Even when the glass is extracted with organic solvents, only a fraction of the deposit is dissolved. Therefore, even a quantitative analysis of the IR spectrum of the extract provides values smaller than the true coverage due to incomplete extraction.
- ItemRecommended procedure for the IR spectroscopic determination of water in soda-lime-silica glass : Report of the International Commission on Glass (ICG) Technical Committee 14 "Gases in Glass"(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1999) Geotti-Bianchini, Franco; Geißler, Heinz; Krämer, Fritz; Smith, Ian H.The paper illustrates a procedure recommended by Technical Committee 14 (TC14 "Gases in Glass") of the International Commission on Glass (ICG) for the determination of the water content of soda-lime-silica glass by infrared transmittance spectroscopy, based on the two bands at 2.8 and 3.6 μm using as extincdon coefficients 70 and 150 l/(mol · cm), respectively As shown by the result of two intercomparisons, the agreement on the determined water concentration values can be quite satisfactory, within ±20 ppm, provided the procedure to evaluate the spectral curves is closely specified. The selected extinction coefficients are in reasonable agreement with recent evidence obtained using Nuclear Reaction Analysis.
- ItemInfluence of alumina content and modifiers on phase separation in soda-lime-silica glass(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1998) Geotti-Bianchini, Franco; De Riu, Luca; Sglavo, Vinvenzo M.; Maschio, DalThe phase Separation behaviour of industrial soda-lime-silica glass is studied by visible light scattering. The main aspects which differentiate industrial glass from the ternary glass (composition in wt%): 76 SiO₂, 13 Na₂O, 11 CaO are considered. The obtained results show that the simple ternary glass easily develops phase Separation upon annealing at suitable temperature levels. Conversely, Container glass is stabilized against demixtion by the presence of a significant AI₂O₃ concentration, a significantly lower SiO₂ content and a more complex chemical formulation (partial Substitution of SiO₂, Na₂O and CaO with AI₂O₃, K₂O and MgO, respectively, as well as minor ingredients).
- ItemInfluence of water dissolved in the structure of soda-lime-silica glass on melting, forming and properties: state-of-the-art and controversial issues Report of the International Commission on Glass (ICG) Technical Committee 14 "Gases in Glass"(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1999) Geotti-Bianchini, Franco; Brown, John T.; Faber, Anne J.; Hessenkemper, Heiko; Kobayashi, Sho; Smith, Ian H.The paper summarizes the information available about the water content of soda-lime-silica glass, the factors that influence it and the influence exerted by water in glass on redox and sulphur retention, on fming, on the melting and forming behaviour, workability and the physical and chemical properties of the melt. Such issues were discussed by the authors in their presentations at the first Forum on Water in Glass, organized in 1997 by Technical Committee 14 (TC 14 "Gases in Glass") of the International Commission on Glass (ICG). The present paper reports the conclusions of the final discussion, highlighting the issues on which consensus was reached (IR spectroscopy is suitable to monitor the water content; the water content of conventionally fired Containers is 300 to 400 ppm and daily oscillations are moderate; water, redox and sulphur interact mutually; water lowers the viscosity; the influence of water content variations on the radiative thermal conductivity is moderate) and the still controversial issues (influence of water and hydroxides in the batch on the final water content; influence of water in the batch and atmosphere on the redox State of the glass; influence of oscillations of OH level on the workability; influence of OH level on ease of forming, product quahty and strength).