DuPont model

The mobile phase consisted degassed distilled water containing 1.0 grams/liter of Aeorosol(B)-OT and varying amounts of sodium nitrate, NaNOj. The detector was a DuPont Model 840 UV photometer with a fixed wavelength of 254 nm. 

The pyrolysis of wood, oxygen chemisorption and oxidation of wood chars were carried out in a computerized coupled TG-FTIR system containing Cahn-R-100 electric balance, DuPont Model 990 thermal analyzer and Nicolet MX-1 Fourier transform infrared spectrometer. All of these sequential processes are carried out within the thermal balance without interruption. 

Figure 8 shows the DSC thermogram of griseofulvin obtained with a DuPont Model 900 Thermal Analyzer. A single sharp melting endotherm occurs for this substance with onset temperature at 216 C. 

Figure 9 shows the TG thermogram of griseofulvin obtained with a DuPont Model 950 Thermogravimetric Analyzer. The thermogram shows no weight loss from ambient to about 200°C followed by weight loss due to sublimation. 

A duPont Model 900 Differential Thermal Analyzer shows halcinonide to have one endotherm at 269°. Decomposition on melting precludes differential scanning colorimetry studies for purity. 

The DTA curves in Figures 7 and 8 were obtained with a DuPont Model 900 instrument. Figure 8 shows that the base melts sharply and Figure 7 shows that the hydrochloride melts with decomposition. Visually the hydrochloride melts at 274°C, but decomposition takes place over a large temperature range (Figure 7). 

Dynamic Mechanical and Thermomechanical Analysis. A DuPont Model 981 DMA was used to determine the dynamic modulus and damping characteristics of baseline and irradiated specimens. Transverse composite samples 1.27 cm x 2.5 cm were used so that the modulus and damping data were primarily sensitive to matrix effects. Data were generally determined from -120°C through the glass transition temperature (Tg) of each material using a heating rate of 5°C/min. 

Laminate expansion/contraction characteristics were determined with a DuPont Model 942 TMA. In this test the movement of an 0.38 cm diameter, hemispherical-tipped quartz probe resting on the specimen was monitored as the specimen was heated from room temperature through its softening range. 

Thermal analyses were performed on a Dupont Model 9900 thermal analyzer under nitrogen atmosphere. A heating rate of ICPC/min. was employed for glass transition temperature (Tg) determinations. 

The DSC thermogram of procaine hydrochloride was obtained using a DuPont model TA 9900 computer / thermal analyzer system. The analysis was carried out between 60 and 240"C, and the resulting thermogram is found in Figure 2. The compound was found to exhibit a clear and well-defined melting endotherm, whose temperature inflection was observed at 159<>C. 

Air Samples. Airborne nitrosamines were collected with a Thermo-Sorb/N air sampler (2) connected to a battery-operated pump (DuPont, model P-4000) which had been calibrated using a 500 ml bubble burett. The pumps were operated between 1.5 and... 

Differential Thermal Analysis. High temperature differential thermal analyses were obtained with a Dupont Model 1200 instrument. Samples were heated from room temperature to 950° C at a rate of 20°C/min in a slow stream of hydrogen. Molybdenum cups were used to hold the sample and alumina reference. The instrument was calibrated with sodium chloride (mp 800° C). 

Deactivated catalysts (5.4-5.5 mg) were loaded at ambient conditions into a 0.1 cm id X 2.0 cm quartz tube having one sealed end. Catalyst was held in place with a plug of Amersil quartz wool. Both quartz wool and tubes were baked out at 500°C for one hour prior to use. The loaded tube was placed into the electrically heated tip of the solids probe of a DuPont model 21-491 mass spectrometer operated at 1 X 10 7 torr. The solids probe was located in the mass spectrometer so that its tip, through which desorbing hydrocarbon molecules passed, was immediately adjacent to the ion source. The probe temperature was raised from 38° to 385°C in 22 minutes. Spectral scanning was conducted automatically every 30 seconds from approximately mje 16 to ra/e 650 at 10 sec/decade. 

Dynamic mechanical testing of the epoxy matrix/epoxy sizing blends was done on a DuPont model 983 DMA interfaced to a 9900 model controller. Stoichiometric mixtures of DER 383 and DACH were first prepared, and then sufficient size was added to produce the desired concentration on a weight percent basis. The mixture was degassed and poured into silicone RTV-664 [10] molds that contained four cavities, 3.2 x 12.5 x 60 mm. The specimens were cured at room temperature for 16 h in a desiccator, placed in a forced convection oven, and ramped to 80°C at 5°C/min and held at that temperature for 2 h. The samples were allowed to cool to room temperature and then removed from the mold. The specimens were replaced in the oven on a metal sheet and postcured at 175°C for 2 h. The free surface of the specimens was ground on a Struers Abramin polisher using 320 grit SiC paper and water to produce parallel faces on the specimens. 

The DuPont Model 830 liquid chromatograph (Fig.3.32) makes use of a pneumatic single-displacement pump which works on the pneumatic amplification principle (Fig.3.33). Compressed gas at a pressure of 0—100 p.s.i. is delivered to the large piston head. The amplification factor for this pump is 45 1. Thus pressures of up to 4500 p.s.i. are possible for solvent delivery, although the system has a recommended working range of up to... 

Fig. 3.43. Schema of the DuPont Model 840 single-wavelength detector.

A DuPont model 21-492B GC/MS with an Incos data system was used to confirm the presence of thiazolidine and nitrosated thiazolidine. A 30 m x 0.24 mm id glass capillary column coated with SP-2250 was used for GC/MS analyses with a 30 1 split ratio (with the larger fraction vented to atmosphere through a charcoal trap). Electron impact ionization was used at 70 eV. The data system generated total ion current chromatograms and recorded mass spectra. 

A Perkin-Elmer MPF-2A Fluorescence Spectrophotometer was used to determine the excitation and emission wavelengths required for achieving maximum fluorescence intensity for the pesticides studied. The MPF-2A contained a 150 watt xenon arc and an excitation monochromator with a grating blazed at 300 nm as the excitation unit a Hamamatsu R 777 photomultiplier tube (sensitivity range 185 - 850 nm) and an emission monochromator grating blazed at 300 nm as the emission detection unit. A DuPont Model 848 Liquid Chromatograph was used for HPLC (Figure 2). The accessory injection device included a Rheodyne Model 70-10 six-port sample injection valve fitted with a 20 y liter sample loop. A Whatman HPLC column 4.6 mm x 25 cm that contained Partisil PXS 1025 PAC (a bonded cyano-amino polar phase unspecified by the manufacturer) was used with various mobile phases at ambient temperature and a flowrate of 1.25 ml/minute. 

Analysis. The percent solids of each of the latexes was measured using a DuPont Model 950 Thermogravimetric Analyzer. Solution densities were determined using a Parr Mettler Model DMA-60 precision densitometer. The particle density was calculated from the solution density and the percent solids. 

Thermogravimetry (TG) data were obtained on the NH4+- and H30+-exchanged ZSM-5 samples, as well as on a separately prepared NH -exchanged sample of similar composition, for confirmation purposes. A duPont Model 951 thermogravimetric analyzer was used in conjunction with a Model 990 Recorder-Controller. The TG curves were obtained on approximately 25 mg samples, at a heating rate of 10°C per minute, and under flowing air at a rate of 38 cnP per minute. 

A DuPont Model 990 thermal analyzer equipped with a Model 910 DSC cell base was used for differential scanning calorimetry. Samples were analyzed as 15 (w/w) solutions of freeze-dried RDP which had been dialyzed to remove excess buffer salts. A heating rate of 5°C/min was used runs were performed in a nitrogen atmosphere (5 psi). A known weight of water was used in the reference pan to balance the heat capacity of the sample pan. 

Thermogravimetric Analyses. All thermogravimetric analytical data were obtained on a DuPont Model 950 Thermogravimetric Analyzer. The atmosphere over the sample was helium gas which had been passed through molecular sieves. The helium flow rate was kept constant throughout all experiments at 60 ml./min., and the sample heating rate was 10°C./min. Attempts were made to keep the sample masses used as nearly the same as possible (10 mg.), to maximize comparability. 

Figure 21. Differential scanning calorimetry and thermogravimetry of oxygen chemisorption on cellulose char at 118 C. The analysis was carried out on 2.5-mg samples in aluminum pans using a Cohn R-lOO electrobalance and a DuPont calorimeter cell attached to a DuPont model 990 thermal analyzer, and nitrogen and oxygen gas flows (60 mL/min, dried by passing through H2SO4) were rapidly interchangeable for DSC and TG.

A DuPont Model 990 Thermal Analysis Console with Model 910 DSC accessory was interfaced to a minicomputer system by means of a microcomputer for automated data collection. A program to provide the analysis of reaction kinetics data by the single dynamic scan method for DSC kinetics was developed. Features of this program include a fit of the data to a single equation by multiple regression techniques to yield the reaction order, the energy of activation and the Arrhenius frequency factor. The rate constant k(T) is then calculated and conversion data as a function of time and temperature can be generated at the operator s option. 

TG-DTG measurements were made with a DuPont Model 951 thermo-gravimetric analyzer equipped with a 1091 disk memory. Weight loss data were obtained as a function of time and temperature. Samples were heated from room temperature to 900°C at a rate of 10°C/min. The purge gas was ultra-pure nitrogen, typically at... 

Photolysis studies were performed on freshly prepared solutions of the photoinitiator, (4xlO-3g/mL in hexane), the stabilizers (lxlO 3g/mL hexane), and combinations of the photoinitiator and stabilizer solutions. Solutions were degassed with dried N2 and photolyzed for 27 s with a broad band, high pressure Hg lamp (200-400 nm 0.030 J/s-cm2). The photolyzed samples were analyzed within 4 h on a DuPont Model 850 HPLC System equipped with a CN column. The solvent systems, CHCl3/hexane or IPA/hexane, were pumped at 1.5 mL/min. Products were detected at 280 nm with a minimum of five injections used for each analysis. 

Melting points and glass transition temperatures were determined in the usual way by use of a differential scanning calorimeter (Dupont Model 900). Heating rate was 11° C/min. 

The DTA measurements were made on a DuPont Model 900 Thermal Analyzer using a heat-up rate of 20°C./min. 

Thermal gravimetric analyses (TGA) were carried out on a DuPont model 951 analyzer. 

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