Melts measurement

Fig. E5.6 Rate of melting of a 2 x 2-in block of HDPE on a hot rotating drum, (a) Drum temperature at 154°C. (b) Drum temperature at 168°C. Rate of melting measured in volume of displaced solid. [Reprinted by permission from D. H. Sundstrom and C. Young, Melting Rates of Crystalline Polymers under Shear Conditions, Polym. Eng. Sci., 12, 59 (1972).]...

We think that judicious application of molecular simulation tools for the calculation of thermophysical and mechanical properties is a viable strategy for obtaining some of the information required as input to mesoscale equations of state. Given a validated potential-energy surface, simulations can serve as a complement to experimental data by extending intervals in pressure and temperature for which information is available. Furthermore, in many cases, simulations provide the only realistic means to obtain key properties e.g., for explosives that decompose upon melting, measurement of liquid-state properties is extremely difficult, if not impossible, due to extremely fast reaction rates, which nevertheless correspond to time scales that must be resolved in mesoscale simulations of explosive shock initiation. By contrast, molecular dynamics simulations can provide converged values for those properties on time scales below the chemical reaction induction times. Finally,... 

Although several techniques have been used to characterize stereosequence distribution, we suggest that the percent crystallinity and temperature of melting measurements are more generally applicable than any other technique presently available. Bovey and co-workers (7) showed how NMR measurements can be used to determine the triad distribution in polymers such as polymethyl methacrylate in which there is sufficient difference between the NMR spectra corresponding to syndiotactic, isotactic, and heterotactic triads to allow quantitative measurements to be made. This type of measurement unfortunately is restricted to few systems and would lead to a unique description of the stereostructure of the chain only when a model involving one or two probability parameters is applicable (See Appendix I). 

Miinstedt H (1979) New universal extensional rheometer for polymer melts. Measurements on a polystyrene sample. J Rheol 23 421-36. 

Gramespacher H and Meissner J (1992) Interfacial tension between polymer melts measured by shear oscillations of their blends. J Rheol 36 1127-41. 

The values of the evaporation and sublimation heats are usually quite close to each other, as well as the densities of solid substances and their melts, measured at the melting point. Consequently, the values of the surface energy at the liquid-vapor, aLV, and at the solid-vapor, osv, interfaces are nearly identical. Oppositely, the interfacial energy oSL at the interface between the solid phase and its melt is usually low oSL values normally do not exceed 1/10 of surface tension values of melt (note that the heats of melting are also on the order of -10% of those of evaporation). 

Zhang Y (1999) H2O in rhyolytic glasses and melts Measurement, speciation, solubihty, and diffusion. Rev Geophys 37 493-516... 

Figure 5.1 (a) DSC thermograms and (b) the temperature dependence of infrared absorbance estimated for the D and H infrared crystalline bands in the cooling process from the melt measured for a series of DHDPE/LLDPE(2) blend samples. The starting temperature of crystallization is slightly different between these two curves probably because of the difference in the cooling rate, the monitoring point of temperature, and so on. But essential behavior is the same. 

Figure 19. Hysteresis of ds-DNA melting measured by a.c. polarography height 0 and Q),--peak potentials of 0 and 0.

Rheological characterization on thermoplastic melts measures material flow properties and provides vital information about polymer processing. Blow molding materials are expected to be more viscous than would normally be employed for the injection molding process [55]. It is also possible to separate the polymer by identifying their MFl values. 

The concentration of -alkanes with carbon chain length C20 can be correlated to the heats of crystallization or of melting measured in the sample, and the maximum temperature of crystallization can be related to the temperature of the pour point. The precipitation of paraffins and therefore pour points at a temperature of +20 °C, as measured on the crude of... 

A simple but unquestionable method has been used to investigate high-temperature hydrolysis of molten KCl-NaCl. A mixture of HCl and H2O obtained by passing an inert gas through aqueous solutions at a definite concentration was passed into the melt. Measurements of the equilibrium O concentration by potentiometric method allowed to calculate the equilibrium constants of [10.4.13] as pK=55.3xl0 T -40.2. At 1000, pK=15.1, it means that equilibrium [10.4.13] in molten KCl-NaCl is displaced to the left. 

A study using confocal Raman spectrometry was carried out to determine the concentration profile within the extrudate of rubbery particles in a polyethylene matrix during capillary flow (Chartier et al. 2010). Chartier et al. reported that the effect of the concentration of particles on the apparent viscosity of polymer melts measured using capillary flow was the opposite of that based on observations made using linear dynamic viscosity measurements (Fig. 7.41). Shear-induced migration can be detected from the concentration profile of the components of the... 

Growth Rate of Miscible Polymer Blend Spherulites Crystallized Isothermally from the Melt Measured by Polarizing Optical Microscopy [74]... 

The electrolysis experiments were carried out with TiOj anodes, as preliminary experiments had showed that such anodes are rather stable on electrolysis in CaClj melt. Measurements of Ti02 solubility in different melts [4] are given in Table 2. 

Experimentally, we do not have any data on the diffusion of trapped chains in a network. What is available is the diffusion coefficient of a labeled chain in polyethylene melts, measured by two techniques 1) from nuclear spin resonance data, and 2) using deuterated chains as labels, the local concentrations of deuterated/protonated species being probed by infrared measurements. ... 

Higgins et al. measured f) for polytetrahydrofuran in CSj and in the melt. Measurements were taken on both the conventional back-scattering spectrometer, giving S(Q,w), and the new neutron spin echo spectrometer (NSE), which measures S Q,t) directly. The agreement between the two sets of data was good and it was found that in solution and Q J- - - in the melt, with the melt values... 

Figure 2.49. Melting curves of poly(butylene terephthalate) at various heating rates showing recrystaUization during melting. Measurements made on Hoechst Celanese PBT1600A. Sample preparation 10°Omin coohng from 250°C, then the samples were heated for analysis at the rates indicated at the curves. (Endotherm is down) (Menczel, unpublished results.)...

Rg. 16-5. Storage compliance of linear pdyethylene crystallized from the melt, measured at 10 different temperatures as shown. Open circles, from forced oscillation half black, from free vibration black, calculate indirectly from creep measurements. (Nakayasu, Markovitz, and Plazek. )... 

Verlaek et al. [50] have used mid-IR for the determination of the non-UV absorbers Zn-stearate, Ca-stearate and oleamide (SEP values 29, 12 and 49 ppm, respectively in the melt as compared to 57, 37 and 34 ppm on film for typical nominal values of 450-1000 ppm oleamide and 1500 ppm stearates). It is again noticed that melt measurements using a 14 mL mini-extruder at 190°C often outperform polymer film measurements. SEP values for mid-IR measurements on LDPE melt containing Chimas-sorb 944, Irgafos 168, Irganox 1010/1076 were ca. 16 ppm for a complete additive package in fixed ratio concentrations (combinations of Chimassorb... 

Mttnstedt, H., New univmsal exiensional rheometer for polymm melts measurements on a polystyrene sanqtle, J. BheoL, 23,421-436 (1979). 

Via small angle neutron scattering in the melt. Measured by neutron-spin-echo. Measurement at 435 K... 

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