Band drying oven

Purification and Characterization. Recrystallize the crude (E)-stilbene from 95% ethanol in a small Erlenmeyer flask or a test tube. Collect the re-crystalHzed material by vacuum filtration using a Hirsch funnel. Maintain the vacuum for an additional 10 min to partially dry the crystalline product. Now place the material on a clay plate, or on filter paper, and allow it to air-dry thoroughly. As an alternative procedure, the final traces of water may be removed by placing the sample (use an open test tube with the mouth covered by filter paper retained by a rubber band) in a vacuum drying oven (or pistol) for 10-15 min at 30 °C (1-2 mm). 

The polyimide is formed by the thermal polycyclocondensation of the poly(amide acid). For this purpose, 5 ml of poly(amide acid) solution are placed on a watch glass (diameter 10 cm) and kept in a vacuum oven at 50 °C for 24 h.The solvent evaporates and at the same time cyclization to the polyimide takes place the resulting film is insoluble in dimethylformamide.The formation of the polyimide can be followed by IR spectroscopy the NH-band at 3250 cm disappears while imide bands appear at 1775 and 720 cm" Once the initial drying process has raised the solid content to 65-75%, the polyimide formation can be accelerated by heating the poly(amide acid) film to 300 °C in a vacuum oven for about 45 min.The polyimide made from pyromellitic dianhydride and 4,4 -oxydianiline exhibits long-term stability in air above 200 °C. 

The collected volatiles were desorbed from the Tenax TA at 260°C using a modified GC packed-column injector. A 25 G, 2.5 inch needle at one end of the injector was inserted through the GC septum, and the Tenax sample tube was placed into the injector through a screw cap at the other end. The desorbed volatiles were carried through the injector by a flow of helium and were trapped as a sharp band at the beginning of the GC column by maintaining the GC oven temperature at -40°C with dry ice for the 15 min desorption period. The helium carrier gas supplied by the GC was turned off as long as the needle of the desorption unit was inserted into the GC. 

An alternative method was also studied. This involved ratioing the intensity of the 698 cm 1 styrene band to the intensity of the 2921 cm-1 C-H stretching vibration. Since oils and other additives would interfere with this approach they were extracted with acetone. Vacuum oven drying was then necessary to remove all traces of acetone prior to PA analysis. Otherwise the PA spectrum would be that of acetone rather than that of the rubber since the gas phase spectrum of the acetone would overwhelm that of the solid phase rubber. This technique allowed both solution and emulsion SBR to be analysed by a common method. The results can be expressed by a least squares linear regression equation over the range of 5%-40% styrene in SBR. 

Polychloroprene (Neoprene W or AC Soft, E. I. duPont de Nemours and Co.) was dissolved in toluene, precipitated in methanol, and dried in a vacuum oven at room temperature. This procedure was repeated three times. The polymer was used immediately after the last precipitation. Neoprene W and Neoprene AC Soft have Mns of 180,000 and 230,000, respectively, and allylic chloride contents of 1.45 and 0.77 mol%, respectively. The Mns were determined by osmometry, and mol% allylic chloride are based on an IR measurement of the 1,2-addition-product band of polychloroprene at 921 cm"1 (5). PTHF used for DTA and stress-strain measurements had TvTn = 95,000. 

These models use experimental data from drying kinetics tests in a laboratory, pilot-plant or full-scale dryer, and are thus more accurate and reliable than methods based only on estimated drying kinetics. They treat the dryer as a complete unit, with drying rates and air velocities averaged over the dryer volume, except that, if desired, the dryer can be subdivided into a small number of sections. These methods are used for layer dryers (tray, oven, horizontal-flow band, and vertical-flow plate types) and for a simple estimate of fluidized-bed dryer performance. For batch dryers, they can be used for scale-up by refining the scoping design calculation. 

Near-IR photoacoustic spectra have been reported for talc and other minerals [38]. Samples were passed through a 240-mesh (64jim) sieve, and were ground first if necessary. The powder was oven-dried overnight at 105°C prior to analysis. Bands were observed at 1.4S (O-H band), 2.14, 2.18, 2.27, 2.36, 2.43, and 2.S0 /tm. The UV-visible photoacoustic spectrum was featureless. 

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