Thermal analysis bulk liquid temperature

Liquid sulfur-dicyclopentadiene (DCP) solutions at 140°C undergo bulk copolymerization where the melt viscosity and surface tension of the solutions increase with time. A general melt viscosity equation rj == tj0 exp(aXH), at constant temperature, has been developed, where tj is the viscosity at time t for an S -DCP feed composition of DCP mole fraction X and rj0 (in viscosity units), a (in time 1), and b (a dimensionless number, -f- ve for X < 0.5 and —ve for X > 0.5) are empirical constants. The structure of the sul-furated products has been analyzed by NMR. Sulfur non-crystallizable copolymeric compositions have been obtained as shown by thermal analysis (DSC). Dodecyl polysulfide is a viscosity suppressor and a plasticizer for the S8-DCP system. 

Pentyl-4 -cyanobiphenyl and 4-octyl-4 -cyanobiphenyl liquid crystals (LCs) confined in molecular sieves of MCM-41 and cloverite types are studied in a wide temperature range by dielectric spectroscopy, thermal analysis and in-situ FTIR spectroscopy. The phase transitions of the bulk LCs cannot be detected when confined in MCM-41 sieve. A relaxational process occurs due to the molecular motions in the layer at the pore walls the temperature dependence of the characteristic frequency obeys a Vogel-Fulcher-Tamman law associated to a glassy state. In the cloverite cages, the LCs keep the phase transitions of the bulk but shifted. Interactions between Lewis and Brdnsted sites and the LC molecules are monitored by IR spectroscopy. DTA measurements put also in evidence strong guest-host interactions. 

Thermoporometry is a technique that allows the pore structures of materials in the liquid state to be studied to determine the pore size distribution in porous media by means of the Gibbs-Thomson equation (Brun et al., 1977). The principle of the method is based on the decrease of the triple point temperature of a liquid filling a porous material. Importantly phase transitions, such as crystallization or melting, for a liquid confined within a pore can shift to lower temperatures which can be correlated to pore size. This difference in transition temperature between confined and bulk solvent can be analysed by differential thermal analysis or differential scanning calorimetry techniques. 

Transient infrared spectroscopy (TIRS) is a mid-infrared technique [82] that has been developed to obtain spectra of moving solids and viscous liquids. TIRS spectra are obtained from the generation of a thin, short-lived temperature differential that is introduced by means of either a hot or cold jet of gas. When a hot jet is used, an emission spectrum is obtained from the thin, heated surface layer. This technique is known as transient infrared emission spectroscopy (TIRES). When a cold jet is used, the blackbody-like thermal emission from the bulk of the sample is selectively absorbed as it passes through the thin, cooled surface layer. The result is a transmission spectrum convoluted with the observed thermal spectroscopy. This method is known as transient infrared transmission spectroscopy (TIRTS). TIRS is ideally suited for online analysis because it is a single-ended technique that requires no sample preparation. This technique has been applied to the lignin analysis of wood chips [83]. 

Analysis of data following procedures analogous to the use of equations 22,23,37, and 38 can provide values for/o and j8/ (if B is set equal to unity). This has been done successfully for the pressure dependence of viscosities of some ordinary liquids and of bulk relaxation times of polyvinyl acetate. For the latter, the value of /o at a particular reference temperature found from pressure dependence is consistent with that found from temperature dependence. In all cases, j8/ is less than half of jS, so the major portion of the volume change in compression is due to reduction of the occupied volume—in contrast to thermal expansion, where the major portion (often about two-thirds) is due to increase in the free volume. The compressibility jS/ is presumably closely similar to the difference Aj3 between the total compressibilities just above and just below Tg. This identification is subject to an important reservation, however, as described in Section 2 below. 

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