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  • 1
    Electronic Resource
    Electronic Resource
    Determination of the Glass Transition Temperatures of Some New Methyl Methacrylate Copolymers Using Modulated Temperature Differential Scanning Calorimetry (MTDSC) (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 1464-1469 
    Details
    ISSN: 1573-904X
    Keywords: dynamic differential scanning calorimetry ; thermogravimetric analysis ; methyl methacrylate ; surface area ; graft copolymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purpose of this study was to determine the glass transition temperatures of new graft copolymers using Modulated Temperature Differential Scanning Calorimetry (MTDSC), and to assess the differences between starch and cellulosic derivatives of methyl methacrylate and between two different drying methods used in their preparation. Methods. Graft copolymers of methyl methacrylate were synthesized and dried by oven or freeze-drying. Surface area measurements and different thermal analysis techniques (Differential Scanning Calorimetry (DSC), Thermogravimetric analysis (TGA) and MTDSC) were used to characterize these copolymers. Results. DSC was not sensitive enough to identify the Tgs of the copolymers, however they were clearly identifiable by MTDSC. Tg values obtained may depend on the method of preparation that also altered their physical characteristics e.g. specific surface area. Cellulose derivatives showed lower Tgs than starch derivatives. The results also depended on the drying method used, thus, freeze dried products had slightly lower Tgs than oven dried products. Conclusions. MTDSC represents a useful thermal technique that allows the identification of glass transitions in these new copolymers with higher sensitivity and resolution than conventional DSC, separating the transition from overlapping phenomena such as decomposition or dehydration. The Tg of this new class of copolymers appeared to be dependent on polymer composition and drying method used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018971630036
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  • 2
    Electronic Resource
    Electronic Resource
    Study of the Porous Solids Obtained by Acid Treatment of a High Surface Area Saponite (1999)
    Springer
    Journal of porous materials 6 (1999), S. 335-344 
    Details
    ISSN: 1573-4854
    Keywords: saponite ; acid treatment ; surface area ; porosity ; acid centres
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new deposit of saponite, Vicálvaro (Madrid, Spain), has recently been described in the Madrid Basin (provinces of Madrid and Toledo, Central Spain). The acid treatment of such material and the characterization of the solids obtained are reported in the present paper. The surface area of the natural saponite is rather high, 197 m2/g, related to the very small size of the clay particles due to the sedimentary origin of the deposit. The treatment of the saponitic material at room temperature with 0.62 wt% HCl for times of between 2 and 48 h or with 1.25 wt% HCl solutions for times of up to 6 h produces a partial dissolution of the saponite structure, resulting in the formation of mixtures of unattacked saponite and free silica, with a high development of the textural properties of the solids. The treatment with 1.25 wt% HCl solutions for times of over 6 h results in an almost total dissolution of the structure of the clay, the obtained solids being mainly formed by some delaminated saponite sheets, free silica and insoluble impurities. Solids with a maximum surface area of 462 m2/g and a maximum number of acid centres of 0.98 mmol H+/g are obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009657312123
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    Paper (German National Licenses)
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