Measurement rate glass transition temperature

Measurement of Glass Transition Temperature (Tg). obtained polymers were measured by DSC analysis (Du Pont Inc., 910 model) at a heating rate of 20°C/min. 

Class-Transition Measurements. The glass-transition temperature, Tg, was measured using a Mettler TA3000 differential scanning calorimetry instrument with a scan rate of 20 °C/min the second scan was measured to determine Tg. 

Thermal Characterization. The DuPont 941 Thermal Mechanical Analyzer (TMA), attached to a model 900 thermal analyzer, was used for the measurement of glass transition temperature (Tg). The heating rate was set at 10 C/min. For wet samples, about 0.05 ml of distilled water was dropped into the TMA sample holder tube before running the experiments, to maintain the sample in a water saturated state during the measurement. 

Thermal Properties. Thermal properties include heat-deflection temperature (HDT), specific heat, continuous use temperature, thermal conductivity, coefficient of thermal expansion, and flammability ratings. Heat-deflection temperature is a measure of the minimum temperature that results in a specified deformation of a plastic beam under loads of 1.82 or 0.46 N/mm (264 or 67 psi, respectively). Eor an unreinforced plastic, this is typically ca 20°C below the glass-transition temperature, T, at which the molecular mobility is altered. Sometimes confused with HDT is the UL Thermal Index, which Underwriters Laboratories estabflshed as a safe continuous operation temperature for apparatus made of plastics (37). Typically, UL temperature indexes are significantly lower than HDTs. Specific heat and thermal conductivity relate to insulating properties. The coefficient of thermal expansion is an important component of mold shrinkage and must be considered when designing composite stmctures. 

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. 

Glass transition temperatures of the uv-hardened films were measured with a Perkin Elmer Model DSC-4 differential scanning calorimeter (DSC) that was calibrated with an indium standard. The films were scraped from silicon substrates and placed in DSC sample pans. Temperature scans were run from -40 to 100-200 °C at a rate of 20 ° C/min and the temperature at the midpoint of the transition was assigned to Tg. 

GPC measurements were used to demonstrate that a monomodal molecular weight distribution with a polydispersity of approximately 2 was obtained. The glass transition temperature was determined on a Perkin-Elmer DSC-2 using a heating rate of 10 C/min and the intrinsic viscosity was determined in NMP at 25°C. These data are summarized in Table I. 

The glass transition temperature can be measured in a variety of ways (DSC, dynamic mechanical analysis, thermal mechanical analysis), not all of which yield the same value [3,8,9,24,29], This results from the kinetic, rather than thermodynamic, nature of the transition [40,41], Tg depends on the heating rate of the experiment and the thermal history of the specimen [3,8,9], Also, any molecular parameter affecting chain mobility effects the T% [3,8], Table 16.2 provides a summary of molecular parameters that influence the T. From the point of view of DSC measurements, an increase in heat capacity occurs at Tg due to the onset of these additional molecular motions, which shows up as an endothermic response with a shift in the baseline [9,24]. 

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