Thermal analysis glass transitions

Table 1. Thermal analysis glass transition temperatures and crystallization effects (melt temperatures of crystallites)...

Thermal Analysis Glass transition temperatures, Tg s, were obtained by differential scanning calorimetry on a Seiko DSC 210. Scans were run at 10 C per minute and the reported values were obtained from a second heating after quick cooling. The thermooxidative stability was determined by thermogravimetric analysis in air on a Perkin-Elmer TGA-7 at 10 /minute heating rate. 

Interesting comparisons have been made 17 between dendritic and the hyperbranched structures the thermal properties (glass transition temperature and thermogravimetric analysis) were independent of architecture and their solubilities were comparable, but greater than that shown for linear counterparts. 

Thermal analysis are widely used for polymers and copolymers analysis. Glass transitions, melting, and decomposition processes are analyzed. Since the glass transition temperature Tg is marked by changes in the thermal capacity, expansion coefficient, and rigidity, TMA technique as well as DSC may be used. Tg increases with molecular mass up to certain values. Plasticizers and water depress this temperature. Thermal stability and influence of antioxidants and fillers may be analyzed by TG or DSC, under oxygen. 

Two copolymers were synthesized with different ratios of the fluorene-based monomer and the fluorenylidene linker. Both polymers were obtained in high yields and high molecular weight with Mw = 55,000-89,500 Da and exhibited excellent thermal stability. Glass transition temperatures ranged from 153 °C to 197 °C with decomposition temperature (5% weight loss measurend by TGA analysis) of 440 to 450 °C. 

The thermal behavior of starch-based composites includes glass transition and thermal decomposition. Glass transition (Tg) is characterized by dynamic mechanical analysis (DMA), dynamic mechanical thermal analysis (DMTA), and differential scanning calorimetry (DSC). Thermal decomposition is determined by using thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG). 

Additional information on elastomer and SAN microstmcture is provided by C-nmr analysis (100). Rubber particle composition may be inferred from glass-transition data provided by thermal or mechanochemical analysis. Rubber particle morphology as obtained by transmission or scanning electron microscopy (101) is indicative of the ABS manufacturing process (77). (See Figs. 1 and 2.)... 

Thermal Properties. Spider dragline silk was thermally stable to about 230°C based on thermal gravimetric analysis (tga) (33). Two thermal transitions were observed by dynamic mechanical analysis (dma), one at —75° C, presumed to represent localized mobiUty in the noncrystalline regions of the silk fiber, and the other at 210°C, indicative of a partial melt or a glass transition. Data from thermal studies on B. mori silkworm cocoon silk indicate a glass-transition temperature, T, of 175°C and stability to around 250°C (37). The T for wild silkworm cocoon silks were slightly higher, from 160 to 210°C. 

The thermal glass-transition temperatures of poly(vinyl acetal)s can be determined by dynamic mechanical analysis, differential scanning calorimetry, and nmr techniques (31). The thermal glass-transition temperature of poly(vinyl acetal) resins prepared from aliphatic aldehydes can be estimated from empirical relationships such as equation 1 where OH and OAc are the weight percent of vinyl alcohol and vinyl acetate units and C is the number of carbons in the chain derived from the aldehyde. The symbols with subscripts are the corresponding values for a standard (s) resin with known parameters (32). The formula accurately predicts that resin T increases as vinyl alcohol content increases, and decreases as vinyl acetate content and aldehyde carbon chain length increases. 

These techniques help in providing the following information specific heat, enthalpy changes, heat of transformation, crystallinity, melting behavior, evaporation, sublimation, glass transition, thermal decomposition, depolymerization, thermal stability, content analysis, chemical reactions/polymerization linear expansion, coefficient, and Young s modulus, etc. 

Network properties and microscopic structures of various epoxy resins cross-linked by phenolic novolacs were investigated by Suzuki et al.97 Positron annihilation spectroscopy (PAS) was utilized to characterize intermolecular spacing of networks and the results were compared to bulk polymer properties. The lifetimes (t3) and intensities (/3) of the active species (positronium ions) correspond to volume and number of holes which constitute the free volume in the network. Networks cured with flexible epoxies had more holes throughout the temperature range, and the space increased with temperature increases. Glass transition temperatures and thermal expansion coefficients (a) were calculated from plots of t3 versus temperature. The Tgs and thermal expansion coefficients obtained from PAS were lower titan those obtained from thermomechanical analysis. These differences were attributed to micro-Brownian motions determined by PAS versus macroscopic polymer properties determined by thermomechanical analysis. 

Glass transition temperature (Tg), measured by means of dynamic mechanical analysis (DMA) of E-plastomers has been measured in binary blends of iPP and E-plastomer. These studies indicate some depression in the Tg in the binary, but incompatible, blends compared to the Tg of the corresponding neat E-plastomer. This is attributed to thermally induced internal stress resulting from differential volume contraction of the two phases during cooling from the melt. The temperature dependence of the specific volume of the blend components was determined by PVT measurement of temperatures between 30°C and 270°C and extrapolated to the elastomer Tg at —50°C. 

Thermal Properties. The glass transition temperature (Tg) and the decomposition temperature (Td) were measured with a DuPont 910 Differential Scanning Calorimeter (DSC) calibrated with indium. The standard heating rate for all polymers was 10 °C/min. Thermogravimetric analysis (TGA) was performed on a DuPont 951 Thermogravimetric Analyzer at a heating rate of 20 °C/min. 

Thermal analysis No test Same as USP stds. endotherm and exotherm units — 6° (HDPE), and 8° (LDPE) Same as USP stds. endo and exo limits—9((PET), none for PETG, glass transition within 4° (PET), 6° (PETG)... 

Phase transitions, whether first-order or second-order, are potent sources of instability of solid drugs and can usually be detected and studied by thermal methods of analysis (e.g., DSC, TGA, TMA, ODSC, DMA, DEA). In crystalline solids, typical first-order transitions are polymorphic or desolvation transitions. In amorphous solids, second-order transitions, such as glass transitions, are common. 

ASTM E 1356-98, ASTM Book of Standards 2002. Standard Test Method for Assignment of the Glass Transition Temperature by Differential Scanning Calorimetry or Differential Thermal Analysis . ASTM International, Conshohocken, PA. 

Wunderlich, B. 1994. The nature of the glass transition and its determination by thermal analysis. In Assignment of the Glass Transition (R.J. Seyler, ed.), pp. 17-31. American Society for Testing and Materials, Philadelphia, PA. 

Temperature(s). See also Blackbody temperature sensor Cure temperature Curie temperature Eutectic temperature Fictive temperature Furnace temperature Glass- transition temperatures Heat entries Heating Hot entries Refrigeration Target temperature emperature measurement Thermal entries Thermo-entries Transition temperatures in analysis of water, 26 35 biofiltration system, 10 76 in biological wastewater treatment,... 

ISO 11359-2, Plastics - Thermomechanical analysis (TMA) - Part 2 Determination of coefficient of linear thermal expansion and glass transition, 1999. 

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