Thermal Analysis of Glasses

Thermal analysis of glasses using the differential scanning calorimeter has become a major technique for determination of the effect of temperature on glasses. The speed of measurement, combined with the small sample size and ease of sample preparation, leads to the use of the DSC for many measurements. Determination of the glass transformation and Active temperatures, crystallization temperatures and kinetics, and estimation of nucleation and viscosity curves have become routine using this instrument. 

Thermal Analysis. The glass transition temperature, Tg, of each of the samples was determined by the use of an Omnitherm Q.C.25 Thermal Analyzer at a heating rate of 20°C/min. The midpoint of the inflection in the DSC output was taken as the Tg. 

D. W. Henderson, Thermal Analysis of Non-Isothermal Crystallization Kinetics in Glass Forming Liquids , Journal of Non-Crystalline Solids, 30 301-315 (1979). 

K. S. Hong and R. F. Speyer, Thermal Analysis of Reactions in Soda-Lime-Silicate Glass Batches Containing Melting Accelerants I One- and Two-Component Systems , J. of the Am. Ceram. Soc., 76 (3) 605-608 (1993). 

Nakamura S, Todoki M, Nakamura K, Kanetsuna H (1988) Thermal analysis of polymer samples by a round robin method. Part I. Reprodubility of melting, crystallization and glass transition temperatures. Thermochim Acta 136 163-178 Ozawa T (1965) A new method of analyzing thermogravimetric data. Bull Chem Soc Jpn 88 1881-1886... 

For all runs, thermal analysis of the resulting polymers showed that only one glass transition temperature could be found. This corresponded to the Tg of the VAc/VEOVA copolymer. Lower glass transition temperatures were found for the semibatch runs, perhaps due to slightly improved VEOVA incorporation. 

Differential Scanning Calorimetry. Thermal analysis of PVME/PS blends and IPNs by DSC indicates only one glass transition temperature, which is located between the homopolymer T s. The position of Tg is dependent upon composition although it does not follow the prediction of the Fox equation (21), Table II. The breadth of the transition also increases significantly with increased PS content for the blends and IPNs. The broad transition might result from either the clustering of like mers near... 

Thermal analysis of DAB-dendr-(CH) and DAB-Je d r-(NH2) shows a number of interesting aspects. The glass transition temperature (Tg) has been derived from... 

Figure 1 Thermal analysis of a fluoride glass showing characteristic temperatures Tg is the glass transition temperamre Tx corresponds to the beginning of the crystalMzation is where the crystalline phase starts to melt 7i is the liquidus temperature corresponding to the end of the melting process...

In another development, thermal analysis of POSS-containing ABA triblock methacrylate/butyl acrylate copolymers (Fig. 4) indicated the presence of two clear glass transitions in the microphase-separated system, with strong physical aging observed in samples annealed at temperatures near the Tg of the poly(methacryl-POSS) phase [122]. 

Figure 2. Thermal analysis of a simple glass ceramic shows an annealing temperature of 500°C, a peak crystallization temperature of 850°C, and a melting temperature of that crystalline phase of 1100°C. These temperatures are approximate temperatures for nucleating (500°C) and crystallizing (850°C) this glass ceramic.

Table I. Thermal analysis of twin models at the glass transition...

Figure 10.11 DTA curve of glass-ceramic sample (Li20-Al203-6Si02). Temperatures of glass transition (Tg), crystallization (Tc) and melting (Tm) are determined from the curve. (Reproduced with permission from R.F. Speyer, Thermal Analysis of Materials, Marcel Dekker, New York. 1993 Taylor Francis Group Ltd.)...

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