Browsing by Author "Preo, Martina"

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    Analysis 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, Martina
    The 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. A 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.
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    CEMS study of tin in the hot end coatings of glass containers
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Geotti-Bianchini, Franco; Preo, Martina; Principi, Giovanni; Maddalena, Amedeo
    Tin oxide coatings are applied to glass containers as adhesion promoters for the organic lubricants. Here, room temperature conversion electron Mössbauer spectroscopy (CEMS) is used to analyse a range of tin oxide coated containers. Readable CEMS curves could be obtained even for the thinnest (30 CTU or about 6 nm) coatings. The hyperfine parameters calculated from the spectral curves show that tin is tetravalent in crystalline form with a preferential grain orientation, which is reduced on annealing. The presence of tin in other oxidation states and dissolved in the matrix was excluded.
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    Intercomparison of IR transmittance measurements on water-containing glasses : Report of the International Commissionon Glass (ICG) Technical Committee14 "Gases in Glass"
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Geotti-Bianchini, Franco; Preo, Martina; Smith, lan H.; Nijnatten, Peter van; Geißler, Heinz; Bucher, Greg
    A previous paper illustrated a procedure recommended by Technical Committee 14 (TC 14 "Gases in Glass") of the International Commission on Glass (ICG) for the determination of the water content of soda-lime-silica glasses by infrared transmittance spec-troscopy. The present paper describes the results of an intercomparison of spectral transmittance measurements performed by TC 14 in order to check the interlaboratory reproducibility that can reasonably be expected when a range of industrial laboratories determines the water content of a given sample. Three samples were circulated within a group of 10 laboratories and for each of them17 spectral transmittance curves were reported, using various spectrophotometers. From each spectrum the corresponding water content value was calculated, using the TC 14 procedure. A statistical elaboration of the results is presented. The spectral transmittance values were affected by a significant spread, with maximum relative deviations up to 14.4 % (maximum relative standard deviation 4.5 %).The spread affecting the corresponding calculated water contents was much smaller, with maximum relative deviations within 4.8 % (maximum relative standard deviation 1.3 %).