Cooling Accessories

Whatever cooling accessory is used, it is important that both it and the DSC have reached thermal equilibrium before any experiments are made. There are a couple of ways to hnd out how long it takes for a particular cooling system to reach equilibrium  

The amount of time required to stabilize will vary considerably between DSCs and cooling systems and may take as long as an hour or two. For busy laboratories that use electrical (mechanical) cooling accessories, the purchase of a power outlet timer can be used to turn the cooling system on an hour or two before the staff start work for the day. A complete calibration procedure should be performed once the DSC and cooling system has stabilized. 

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Cooling accessory for below room temperature studies... 

The use of a cooling accessory permits XRD patterns to be obtained under subambient conditions. In pharmaceutical systems, the greatest utility of the technique is to monitor the crystallization of solutes in frozen solutions. Conventionally, differential scanning calorimetry has been the most popular technique for the characterization of frozen systems. However, as mentioned earlier, this technique has some drawbacks (i) It does not enable direct identification of crystalline solid phase(s). Moreover, it is difficult to draw any definitive conclusions about the degree of crystallinity, (ii) The interpretation of DSC curves is very difficult if there are overlapping thermal events. Low temperature XRD was found to be an excellent complement to differential thermal analysis in the characterization of water-glycine-sucrose ternary systems. " ... 

Standard unit allows operation from ambient to 725X. With optional cooling accessories, the range may be extended to — 170X. 

Temperature range - 50-500°C (subambient temperatures require optional cooling accessory)... 

Dynamic Mechanical Analysis and Stress Relaxation Behavior. Samples were compression molded into bars of the dimensions 38.xl2.5x0.78 0.007 mm and 65.x9.7xl.7 0.007 mm in a Carver laboratory hot press model C. A TA Instruments 983 DMA, which was operated in the fixed frequency mode, was used to characterize the storage and loss moduli as a function of temperature. Samples were scanned at fi-equencies from 0.05 to 10.0 Hz over a temperature range from -150 C to above the glass transition temperature. The displacement was 0.4 - 0.6 mm. Stress relaxation curves were determined for the same size samples at a constant strain. The sample was displaced for 10.0 minutes and then allowed to recover for 10.0 minutes. The stress data were taken in five degree increments. A microprocessor controlled Liquid Nitrogen Cooling Accessory (LNCA) was used for sub-ambient operations. 

Perkin-Elmer DSC 7 equipped with a liquid nitrogen controlled cooling accessory heating rate 5 °C min" . Sample mass ca 10 mg. 

System components are the 983 DMA module, an optional liquid nitrogen cooling accessory, a thermal analyser/temperature controller, data analysis software (model 9000 computer controller or DuPont Thermal-Analyst 2100), and a plotter. 

The importance of the coolant of the sample holder should be emphasized. If a mechanical cooling accessory is used, it should be turned on at least 2 h prior to the actual measurements in order to achieve thermal equihbrium. 

We measured the coefficient of thermal expansion, CTE, of RX-55-AE-5 using a TA Instruments Model 2940 TMA that was controlled by a TA 500 Thermal Analyzer equipped with a TMA Mechanical Cooling Accessory [6,7]. A quartz micro-expansion probe sat on top of all samples with a force of 0.01 Newtons (N). The change in the length of the sample was as it was heated or cooled was measured by a linear transformer that converted the vertical distance of the quartz motion probe and was recorded by the TA Instrument software. Ultra high purity nitrogen carrier gas was used at a constant flow rate of 100 cm /min. Samples were heated at a linear heating rate of 3°C /min. 

Dynamic mechanical analysis was performed in a TA-Q800 DMA and a Gas Cooling Accessory (Model CFL-50) for sub-ambient experimerrts. Film samples were tested in tension mode from -130 °C to 100 °C at a heating rate of 3 C/min and frequency of 1 Hz. 

Dynamic mechanical properties of the irradiated wood was measured using a Pyris Diamond DMA, manufactured by PerkinElmer Life Sciences, Norwalk, CT equipped with a controlled hquid nitrogen cooling accessory. The materials were analyzed in bending mode with the dual cantilever beam fixture for the instrument. 

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