Differential scanning calorimetry sample size

The SCB distribution (SCBD) has been extensively studied by fractionation based on compositional difference as well as molecular size. The analysis by cross fractionation, which involves stepwise separation of the molecules on the basis of composition and molecular size, has provided information of inter- and intramolecular SCBD in much detail. The temperature-rising elution fractionation (TREE) method, which separates polymer molecules according to their composition, has been used for HP LDPE it has been found that SCB composition is more or less uniform [24,25]. It can be observed from the appearance of only one melt endotherm peak in the analysis by differential scanning calorimetry (DSC) (Fig. 1) [26]. Wild et al. [27] reported that HP LDPE prepared by tubular reactor exhibits broader SCBD than that prepared by an autoclave reactor. The SCBD can also be varied by changing the polymerization conditions. From the cross fractionation of commercial HP LDPE samples, it has been found that low-MW species generally have more SCBs [13,24]. 

The DSC thermogram of chlorpromazine hydrochloride shown in Figure 2 was obtained using Du Pont model 9900 differential scanning calorimetry system, using a sample size of 2.83 mg and a heating rate of 10°C/minute [13]. 

In this chapter we investigate the morphology of a series of polyurethanes based on polycaprolactone polyol (PCP), diphenylmethane diisocyanate (MDI), and butanediol (BDO). Samples of as-batch-reacted and solution-cast polymers were examined by optical microscopy, transmission electron microscopy, electron and x-ray diffraction, and differential scanning calorimetry. Our interest is to provide a mapping of the size and shape of the domains (and any superstructure such as spherulites) and the degree of order as a function of the fraction of each phase present. 

The experiments were performed in a lab-scale plant with sample sizes of about 200 - 400 g powder and in a small pilot plant with sample sizes of 1 - 3 kg powder. Depending on the nozzles (orifices 0,4 / 0,5 /1,0 mm, spraying angles 30° and 90°), the kind of PEG (MW 1500/4000/8000/35000) and on pressure (100-250 bar) and temperature (45 - 70 °C) the spraying times reached from about 45 s to 180 s. The obtained particles were characterised by Scanning Electron Microscopy, Differential Scanning Calorimetry and by granulometric analysis. The results can be summarised as follows ... 

Analysis of Major Elements. Major elements were determined quantitatively by neutron activation analysis at the University of Toronto SLOWPOKE reactor. This technique was chosen because the available sample size was small. Differential scanning calorimetry with a Perkin-Elmer DSC-1B was used to establish the plaster composition further and to investigate its thermal behavior. 

Differential Scanning Calorimetry. DSC scans for the M-B-23/25-48 series are shown in Figure 10. At low catalyst concentrations, there are two prominent endotherms at ca. 215°C and 225°C. As catalyst content increases, a new broad endotherm appears at ca. 190°C. These endotherms are characteristic of all polyol systems polymerized at high catalyst concentrations and/or high mold temperatures (Figure 11). Multiple endotherms in MDI/BDO polymers have been previously reported by other investigators (e.g. ref. 4, 14, 16, 17). Overall heats of fusion are a measure of crystallinity and crystal perfection and size and were higher (24 J/g) for samples with low catalyst content. 

Thermal Analysis involves differential scanning calorimetry (DSC) to identify various common engineering plastics. A thumbnail size sliver of the unknown material must be obtained from a location that will not impact the performance of the part, for example the outside edge of the gasket surface on a lined pipe or valve. The sample is sent to a laboratory that can perform DSC. See Figure 7-5. 

Several small-scale screening tests are characterized by the small sample sizes they require (0.01-10 g) and by the speed with which they can be performed. They include differential scanning calorimetry (DSC) and various forms of differential thermal analysis (DTA) the insulated exotherm test (lET), decomposition pressure test (DPT) and the ICI 10 g sealed tube test. Commercial variants of such tests are also available. 

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