Standard DSC pans

Standard DSC Pans. When using these pans, the sample is placed in a disk shaped metal crucible, a flat hd is then placed on top of the sample, and a special device ( crimper ) pushes down the lid on the sample, simultaneously folding the edges of the pan on the lid (see Figs. 2.7 and 2.8). These are the most frequently used DSC pans for polymer measurements the... 

Pan Type. The larger the contact area between the DSC pan and cell, the more reliable the data. So, whenever sublimation of the sample is not a factor, use of standard DSC pans rather than hermetically sealed pans is recommended. 

Often hermetically sealed pans must be used for various purposes. In such cases, the modulation period must be increased somewhat, because the contact area between the pan and the sensor for hermetically sealed pans is smaller than that for standard DSC pans. 

A solution of 3.36 w% initiator in TEGDA was used for DSC, TMS and DMTA measurements. DSC sample weights were about 1 mg, corresponding to a thickness of about 60 fim when aluminum lids of standard sample pans are used. 

The measurements were performed on a DSC Mettler Toledo (DSC822e/400). About 10 mg of each film-forming component or film conditioned at 25°C and 58% RH for 2 days previously was sealed in a standard aluminum pan. The first scan, from 20 to 150°C was applied to remove any thermal history effects. This first scan was stopped before the material melted, and samples... 

Both liquefaction residues were studied by DSC in both inert (dynamic N2) and oxidizing (dynamic air) atmospheres. A computerized DSC system (Perkin-Elmer DSC-2C/TADS) was used in these studies, A flow-thru cover was used with the DSC sample holder asjsembly in all of these studies. Standard gold sample pans were employed for the oxidative profiles obtained in dynamic air atmosphere. For the lower temperature studies conducted in dynamic N2 atmosphere, experiments showed that the results obtained were the same regardless of whether standard aluminum or standard gold DSC pans were employed. All figures given here are hard copy printouts from the Perkin-Elmer Thermal Analysis Data Station. 

The thermal behavior of control PU and its composites were determined using a Perkin Elmer Model DSC-7 differential scanning calorimeter interfaced to Model 1020 controller. The samples were analyzed from room temperature to 250°C (as PU decomposed at a temperature more than 250°C) at a heating rate of 10°C/min. the standard aluminum pan is used to analyze about 10 mg samples under nitrogen gas atmosphere. 

The steady-state calculations have set the stage for computation of the DSC performance without, or better with negligible, temperature gradient within the sample. A temperature gradient within the sample pan should not exceed 2-3 kelvins for typical standard DSC experiments. The first two equations of Fig. 4.67 express the heat-flow rates into the sample and reference making use of Newton s law of cooling (see Fig. 4.9). The heat-flow rate, dQ/dt, is strictly proportional to the difference between block temperature, T, and sample temperature, T. The proportionality... 

The analysis with any unknown sample should start with a trial run using standard DSC, going to the maximum temperature of interest to check if the sample pan stays closed and retains the sample. At high temperatures, many polymers become sufficiently fluid to creep out of the sealed pan or decompose and burst the pan. In this case, a lengthy and difficult cleaning of the DSC head may become necessary, which often reduces the precision of future runs and always requires a full new calibration. It is best to have an old DSC handy for the dirty run. This stability test can also be done in a standard oven fllled with a nitrogen atmosphere. 

The thermal behavior of the film was estimated in terms of its melting endotherm as determined by differential scanning calorimetry (DSC). The DSC was performed using a DSC6200 (SII EXSTAR 6000) with 10 mg samples in standard aluminum pans. The samples were heated at a constant rate of 5°C/min under nitrogen. The measurements were done in the temperature range from -130°C to 250°C. 

A temperature calibration procedure for TMA has been proposed (53-55) and subsequently included as an ASTM method (Test Method for Temperature Calibration of Thermomechanical Analyzers, E1363-90). It uses a penetration probe and the melting temperature of one or more standard materials. Pure metals with sharp melting points are the standards often used. An open DSC pan may be used to contain the calibrant material. Another potential material would be the selected shape memory alloy, reported to be reproducible to 1°C (56). Several reviews on temperature calibration for TMA have been published based on ASTM efforts in this area (54,55). Sircar (26) suggests that, when used for elastomer evaluation, temperature calibration for TMA should be conducted with low melting liquids as in DSC. For calibration of the expansion, one manufacturer s manual (TA Instruments) recommends aluminum for calibrating the linear expansion parameter. Other calibration standards suggested for the linear coefficient of thermal expansion (CTE) are lead (57) and copper (58). 

Never load a sample into a sample pan and run it in a DSC without first performing a preliminary muffle furnace or hot-plate test. This simple test will determine what is the maximum sample size and best pan for the analysis without damaging the calorimeter. The desired results of this test is to choose a sample pan the sample size that will not spill out of the pan and contaminate or damage the DSC. This is accomplished by selecting the pan you think will be best for the analysis. That is usually the cheapest-priced pan. We will assume that the standard aluminum pan will be used. Then crimp 5-, 10-, and 20-mg samples in separate pans and wrap them in foil, mapping the size and position in the foil and place them in a muffle furnace. Heat the furnace up to the maximum temperature of the experiment and hold it there for a few minutes until the temperature is stable. Cool the furnace and then carefully remove the pans from the furnace and unwrap them. 

Figure 2.8. A standard DSC aluminum pan crimped with a standard lid and a lid punched out of aluminum mesh.

All metal standards should be encapsulated in standard aluminum DSC pans. On the other hand, water should be encapsulated in a hermetically sealed aluminum pan. 

Figure 2.80. Time for a UV-curable resin to reach 90% conversion plotted against UV intensity as measured by RT-IR and DPC on a UV-curable resin at 23 °C. Standard A1 DSC pans with PVDF hds were used with nitrogen purge gas. (A. L. Harris and H. E. Bair, unpublished work, 1994.)...

For everyday DSC measurements on polymers, the usual standard aluminum pans should be used (Figs. 2.7 and 2.8). These pans should never be used without a lid, because the major function of the lid is to push down the sample to the bottom of the pan, ensuring good thermal contact. The disadvantage of standard pans is that modern crimpers tightly fold down the pan edge on the lid, so when it is desirable to evaporate some solvent from the sample, the solvent may be slow to leave the pan. In these cases, it is better to punch out lids from aluminum mesh as shown in Figs. 2.7 and 2.8. 

Polymer samples (ca. 5 mg) were encapsulated in standard aluminum pans. DSC examinations were performed with heating and cooling rates of 10 R/min on "as-polymerized samples and on samples previously heated to 450°K, held at this temperature for 5 minutes, and cooled at 10 K/min with baseline correction. The higher of the two melting points on the second melt are reported. DSC melting temperatures. 

The glass transition temperatures of the pure polymers and the blends were measured with a Pcrkin-Elmcr DSC-7 differential scanning calorimeter at a heating rate of 20°C/min for those samples not containing TMS and 10 C/min for samples containing TMS. All measurements were carried out under nitrogen. All samples except those containing TMS were encapsulated in the standard aluminum pans. 

A series of polystyrene molecular weight standards available from the Pressure Chemical Company have been studied by Keinath et al. via thermomechanical analysis. AflYs ranged from nominal molecular weight 2,200 up to 7,200,000. Smooth glassy samples, contained in DSC pans, were prepared by fusing the as-received powdered samples. Tlje weighted probe of the DuPont 943 TMA unit was placed onto the surface of the sample and the entire assembly was heated at S C/min from room temperamre up to a point where the probe had penetrated through the whole thickness of the sample. 

Thermal decomposition was performed using a SDT Q-600 simultaneous DSC-TGA instrument (TA Instruments). The samples (mass app. 10 mg) were heated in a standard alumina 90 il sample pan. All experiments were carried out under air with a flow rate of 0.1 dm3/min. Non-isothermal measurements were conducted at heating rates of 3, 6, 9, 12, and 16 K/min. Five experiments were done at each heating rate. 

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. 

Accurate heat capacity, Cp, measurements may be obtained by DSC under strict experimental conditions, which include the use of calibration standards of known heat capacity, such as sapphire, slow accurate heating rates (0.5-2.0 K/min), and similar sample and reference pan weights. MDSC or DDSC also have been used to determine the heat capacity of several pharmaceutical materials. ... 

---