Viscosity measurement thermal detection

Table 3 summarizes the fluorine content, inherent viscosities, and thermal properties of the synthesized fluorinated polyetherimides The inherent viscosities (for conditions, see footnote of Table 3) of the F-PEI polymers varied from 0.34 to 0.72 dL/g. PEI 7a was obtained at an inherent viscosity of 0.47 dL/g, which is comparable to the value of commercial Ultem 1000 (17 =0.5dL/g). DSC measurements showed that all F-PEIs are amorphous with a Tg range from 220 °C to 247 °C. Within the first series denoted as 7a, 7b, and 7d, Tg between 220 and 224 °C were detected, whereas 7c exhibits a slightly higher Tg of 232 °C. Polymers 8a, 8b, and 8d show Tg between 234 and 236 °C, whereas the Tg of 8c is at 247 °C. 

If an amorphoiis polymer is cooled it will usually attempt to crystallize, but because of the high internal viscosity of the medium it is often precluded from packing into its lowest energy conformation. At 0 K, the lack of thermal excitation prevents the occurrence of most photochemical reactions. As the temperature is increased, the specific volume of the polymer will also increase as a result of forming "free volume", that is, space vdiich is not occupied by hard-shell dimensions of the atoms comprising the polymeric structure. The amount of free volume will depend to a certain extent on the previous thermal history. As free volume increases along with thermal excitation, various kinds of molecular motions will be observed in the polymer vdiich can be detected by I ysical measurements. 

Our ThFFF channel is similar to the model TlOO Thermal Fractionator (FFFractionation, Inc., Salt Lake City, UT), with a channel thickness of 0.10 mm. When the carrier liquid was tetrahydrofuran (THF) or cyclohexane, a UV monitor set at 254 nm was used for sample detection when toluene was the carrier liquid, a refractive index monitor was used instead. The temperature difference was 60.0 K and the cold wall temperature was 298.2 K. Intrinsic viscosities were measured with a CannonFenske ASTM-25 viscometer obtained from Fisher Scientific (Santa Clara, CA). Viscosities were measured in a thermostated temperature bath set at T g. All solvents were high-performance liquid chromatography grade. 

Using pitot tube as a differential pressure detection device, it need to consider factors that affect measurement accuracy, including the pitot tube coefficient, air density, temperature, pressure, thermal expansion coefficient, kinematic viscosity, and installation locations. 

The temperature dependence of the DPH anisotropy in canola oil and paraffin oil is presented as curves a and b, respectively, in Figure 7. Canola margarine was not included because it crystallized at 40°C, the matrix became opaque, and no fluorescence signal was detectable. To correlate viscosity to fluorescence anisotropy, the viscosity of the two oils and the fat were measured by rotational viscometry (Fig. 8) at temperatures above 50°C to ensure that all fat was melted. Samples were equilibrated at 50°C for 6 h prior to measurements to destroy any thermal history of the system. AU samples displayed Newtonian rheological behavior. 

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