PREPARATION OF ULTRAPURE PIVALIC ACID BY RECTIFICATION

A rectification method was developed for the purification of pivalic acid (PVA) on an experimental scale. Ultrapure PVA with a purity of 99.993% was prepared at a rate of 250 mL a week by multistep rectifications, a more convenient and much faster method than the traditional zone refining method. Typical operational conditions were: head pressure around 1 kPa, reboiler temperature 85°C, head vapor temperature 55°C, condenser temperature 36.5°C, and reflux ratio of 6:1. A formula was given to determine the purity of PVA based on the relationship of freezing point and purity. The freezing point of ultrapure PVA, which was obtained by measuring solidification temperature curve using an inner sheath method, is 35.912 ± 0.001°C.     

Ein halbautomatisches Labormeßgerät zur Bestimmung des Trübungspunktes

A Semiautomatic Laboratory Device for the Determination of Turbidity Point A semiautomatic batchwise operating laboratory device is described which can be used for the determination of turbidity point of liquid fatty acids. The region of measurement can be adjusted between 0° and 30°C. Moreover, the region of measurement and the rate of cooling can be varied. This device is currently in use in a plant for the production of fatty acids and it is operated in the region of 0°–10°C at a cooling rate of 0.5°C/min.     

Monitoring experiment and simulation on solidification of DNAN based melt-cast explosive with FBG sensors

In order to obtain the change rule of the temperature field and the mechanism of defect formation during the solidification process of melt-cast explosive, the temperature field change data were tested during the solidification process of DNAN based melt-cast explosive by using an arrayed spatially distributed Fiber Bragg Grating (FBG) temperature sensor device. The temperature field variation during the solidification experiment was obtained under the condition that the cooling rate of the boundary water-bath temperature was 0.2 °C/min. On the basis of the solidification experiments, the macroscopic solidification process of small-caliber grenade at different boundary cooling rates was simulated using ProCAST software. The simulation results show that when the boundary cooling rate is 0.2 °C/min, the temperature fields during the solidification process of DNAN based melt-cast explosive are in good agreement with that of the experimental monitoring points; the size of the melt-cast charge defects decreases as the boundary cooling rate becomes smaller; and the location of the charge defects is closer to the tail of the grenade as the cooling rate decreases. In addition, a mesoscopic model of DNAN based melt-cast explosive was established in the paper. At the mesoscopic level, the generation, formation, and evolution of charge defects in DNAN based melt-cast explosive during solidification were investigated. The study results provide theoretical guidance for the formulation design and process optimization of DNAN based melt-cast explosives, as well as for improving the charge quality of ammunition.     

Eutectic solidification of the quasi binary system of isotactic polypropylene and 1, 2,4, 5-tetrachlorobenzene

This paper describes a study on eutectic solidification of the quasi binary system of un-fractionated isotactic polypropylene and the faceted growing diluent 1,2,4,5-tetrachlorobenzene. According to the Flory-Huggins theory of melting point depression the phase diagram of the present system does not exhibit a eutectic point for equilibrium conditions. However, under experimental circumstances a simple “eutectic-type phase diagram” was found, in which the location of the eutectic point was determined by kinetics to a large extent. The very nature of the eutectic solidification process was found to depend critically on the rate of cooling. At cooling rates lower than 0.5°C/ min the simultaneous crystallisation of the polypropylene and the tetrachlorobenzene proceeded in an uncoupled manner, producing a microstructure consisting of randomly mixed polypropylene spherulites and diluent needles with a characteristic dimension of about 0.1 mm. At speeds of cooling exceeding 0.5°C/min coupled growth of the polymer and the solvent occurred, forming a unique eutectic microstructure of curved diluent crystals homogeneously dispersed in a polymer matrix. The transverse dimension of these particular tetrachlorobenzene crystals was found to be in the micron range.     

Isolation and thermal characterization of high-melting seed crystals formed during cocoa butter solidification

Seed crystals which formed during early stages of cocoa butter solidification have been isolated and determined to have extremely high melting points. The melting points of the seed crystals generally exceeded 60°C, in contrast to cocoa butter, which melts between 30–35°C. In addition, the melting point of the seed crystals decreased as a function of crystal growth time. Evidence suggests that the high-melting seed crystal is not an additional polymorphic form of cocoa butter, but rather a distinct crystalline entity. Consequently, a unique compositional make-up is suspected as being responsible for the elevated melting point. A technique to separate seed crystals from the molten cocoa butter mass has been developed. The procedure has been shown not to alter the thermal and compositional properties of the isolated seed crystals.     

High temperature deformation of non-directionally solidified Al2O3/YAG/ZrO2 eutectic bulk ceramic

Excellent high temperature mechanical properties of melt-grown Al₂O₃-based eutectics have previously been demonstrated in samples prepared by directional solidification methods. In this study, the deformation behaviour of melt-grown Al₂O₃/YAG/ZrO₂ eutectic bulk prepared by a non-directional solidification method was investigated by means of compressive tests in a temperature range of 1200–1700 °C. The non-directionally solidified eutectic bulk ceramic has a colony structure and is polycrystalline. It begins to show ductility and has a compressive strength of 320 MPa at 1500 °C, which is much higher than that of the sintered ceramic with the same composition. However, its plastic deformability is insufficient, even at 1700 °C (just below the melting point of 1715 °C), and cracking occurs during compressive deformation.     

Die Bestimmung von n- und iso-Paraffinen in Kohlenwasserstoffwachsen – Vergleichende Analysenergebnisse der Methoden Gaschromatographie,Harnstoffadduktierung und Molsiebadsorption

Determination of n- and iso-Paraffines in Hydrocarbon Waxes – Comparative Results of Analysis of Gaschromatography, Urea Adduction and Molecular Sieves Adsorption The n- and iso-paraffine content of two refined petroleum paraffines (solidification point 56°C and 66°C) was determined by using a glass capillary column, the splitless cool-on-column-injection and the technic of one column compensation. The n- and iso-paraffine determination of fractions, obtained by the methods of urea adduction (DGF-method M-V7 [75]) and the adsorption on molecular sieves (DGF-method M-V8 [83]) took place in the same way. The selectivity of these two methods of analysis is entered into the particulars.     

Real-time X-ray powder diffraction investigations on cocoa butter. I. temperature-dependent crystallization behavior

The crystallization behavior of cocoa butter has been investigated by means of real-time X-ray powder diffraction. Two procedures have been followed: cooling from 60°C at a constant rate until maximum solidification has taken place; and cooling from 60°C in 2 min to a constant solidification temperature. It appears that all polymorphic forms of cocoa butter, with the exception of the β form, can be formed from liquid. The solidification temperature appears to be the most important crystallization parameter.     

Über die Abtrennung von n-Paraffinen durch Harnstoffaddukt-Bildung

Separation of n-Paraffins by Urea-Adduct Formation Using various procedures for the formation of urea adducts, the determination of n-paraffins in products (solidification point 25°–64°C) containing low, moderate and high concentration of these substances is reported. Theses results are compared with values that are obtained by molecular sieve and antimony pentachloride methods. The authors have established that the determination of n-paraffin by the urea method, as reported in the literature by numerous authors, provides approximate values. The results of the present work indicate that the experimental conditions that are to be employed for the determination of paraffin content by urea-adduct formation, must be adjusted for each type of product after comparing the results obtained by the molecular sieve method. The possibility for the determination of n-paraffins in other petroleum fractions by urea method is discussed.     

Fabrication of aligned lamellar porous alumina using directional solidification of aqueous slurries with an applied electrostatic field

A novel method combining directional solidification of aqueous slurries with an applied electrostatic field was used to fabricate aligned porous alumina scaffolds. A temperature gradient of 1 °C/mm induced a vertical solidification direction. The angle between the temperature gradient and the applied electrostatic field was 90°. As the electrostatic field intensity was increased from 10 to 100 kV/m, the average lamellar spacing of the porous alumina increased from 53.2 to 278.5 μm, and the angle of the lamellar pore channels changed from 7.5° to 52.6° compared to the direction of the temperature gradient. The direction of the lamellar pore channels was a vector sum of the temperature gradient and the electrostatic field intensity. The fabrication of porous alumina with an ordered, lamellar structure can be readily controlled using directional solidification combined with an applied electrostatic field.     

The effect of solidification direction with respect to gravity on ice-templated TiO2 microstructures

Unidirectional ice-templating produces materials with aligned, elongated pores via: (i) directional solidification of particle suspensions wherein suspended particles are rejected and incorporated between aligned dendrites, (ii) sublimation of the solidified fluid, and (iii) sintering of the particles into elongated walls which are templated by the ice dendrites. Most ice-templating studies utilize upward solidification techniques, where solid ice is located at the bottom of the solidification mold (closest to the cold source), the liquid suspension is above the ice, and the solidification front advances upward, against gravity. Liquid water reaches its maximum density at 4 °C; thus, liquid nearest the solid/liquid interface, at 0ºC, is less dense than warmer liquid above (up to 4 °C, above which, a density inversion occurs, and liquid density decreases with increasing temperature). The lower density liquid nearest the solidification front is thus expected to rise due to buoyancy, promoting convective fluid motion in the liquid during solidification. Here, we investigate the effect of solidification direction with respect to the direction of gravity on ice-templated microstructures to study the role of buoyancy-driven fluid motion during solidification. We hypothesize that, for upward solidification, the convective fluid motion that results from the liquid density gradient occurs near the solidification front. For downward solidification, we expect that this fluid motion occurs farther away from the solidification front. Aqueous suspensions of TiO₂ nanoparticles (10–30 nm in size, 10, 15, and 21 vol.%) are solidified upward (against gravity, with ice on bottom and water on top), downward (water on bottom, ice on top), and horizontally (perpendicular to gravity). Microstructural investigation of sintered samples shows evidence of buoyancy-driven, convective fluid flow during solidification for samples solidified upwards (against gravity), including (i) tilting of the wall (and pore) orientation with respect to the induced temperature gradient, (ii) ice lens defects (cracks oriented perpendicular to the freezing direction), and (iii) radial macrosegregation. These features are not observed for downward nor horizontal solidification configurations, consistent with the hypothesis that convective fluid motion does not interact directly with the solidification front for downward solidification.     

Characterization of the high-melting glyceride fraction isolated from cottonseed oil stearin by fractional crystallization in isopropanol

Cottonseed oil stearin is generally produced commercially from cottonseed oil by winterization. In Egypt, the byproduct stearin is often used for lower-priced industrial applications. It can be turned into a high-value, cost-effective edible product by further fractionation to produce low-melting cottonseed oil stearin (LMCS) and a higher melting cottonseed oil stearin (HMCS). In the present investigation, isopropyl alcohol (IPA) helps to obtain good fractionation of HMCS having useful solidification and melting properties. The advantage of using IPA is that fractionation can be carried out at higher temperatures than hexane with better separation efficiency. A direct relationship between yield, quality of HMCS, and crystallization temperature during fractionation with IPA was achieved. HMCS could be fractionated from IPA at 4°C in a much higher yield but the melting point and the solid fat contents were much lower than that fractionated at 18°C. The thermal profile of the HMCS fractionated with hexane lies between those fractionated at 4 and 18°C with IPA. On the other hand, all the LMCS fractions could be considered as good quality salad oils.     

Eine empirische Methode zur Bestimmung der Emulgierfähigkeit von Pflanzenlecithinen in O/W-Systemen

An Empiric Method to Determine the Emulsifiability of Vegetable Lecithins in O/W-Systems The following method has been developed to evaluate the emulsifying effect of native, fractionated and modified vegetable lecithins. The lecithin which is to examine is solved in the ratio 1:9 in a fat mixture with the melting point of 32°C and the solution is given on the surface of 50 ml of water with 50°C, in a graduated cylinder. After 30 min. time of rest the cylinder is turned by hand or by means of a mechanic swinging device 20 times in 20 seconds for 180° about its transverse axis. Afterwards it is placed in a thermostat, with a temperature of 50°C. The time necessary to separate 25 ml water is determined. The thus defined half-life is characteristic for the emulsifying effect of the lecithin. The variation coefficient of the results is about 10% for mechanically emulsifying. The practicability of this method is explicated in many examples.     

Thermal properties of hexadecane encapsulated in poly(divinylbenzene) particles

The thermal properties of n‐hexadecane (HD) encapsulated in crosslinked capsule particles containing a water and/or air domain were studied from the viewpoint of heat‐storage applications. The capsule particles were prepared by the microsuspension polymerization of divinylbenzene at 70°C with the self‐assembling of phase‐separated polymer method that we developed. In the differential scanning calorimetric thermograms, pure HD had a single solidification temperature (T_s) peak at 15°C, whereas the encapsulated HD containing a water domain had two peaks at 6 and 1°C. That is, the encapsulated HD containing the water domain required a longer time and lower temperature to complete the solidification than pure HD, which was negative for heat‐storage applications. However, once the particles were dried and the water domain was replaced with air, the problem with the partially lowered T_s improved. The air domain was also found in the encapsulated HD core after solidification because of the shrinkage of HD. The presence of the air domain did not affect the thermal stability of the encapsulated HD. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

纯水和氯化钠溶液凝固过程的实验研究

近几年国内外学者对冰浆的各种特性进行了大量研究,但大多都集中在冰浆生成器的装置设计、冰浆在管道中的流动及传热特性,很少有从冰晶颗粒在壁面生成及结晶过程的机理进行研究讨论。本文对纯水和不同浓度氯化钠溶液在不同材料表面的凝固特性进行了实验研究,搭建了多组分溶液表面凝固性能研究装置,并对装置布置测点同时可更换测试表面。实验采取不同浓度的氯化钠溶液,分别记录在粗糙度不同的铜板、铝板以及塑料板表面凝固时的温度、时间,分析不同表面粗糙度、不同材质以及氯化钠浓度对溶液成核能的影响。通过对实验数据的分析和处理分别得出开始凝固温度与粗糙度的变化关系以及凝固时间与过冷度的变化关系。实验结果表明：溶液在平板表面凝固的初始温度会随着粗糙度的增大而逐渐升高。溶液在平板表面凝固的凝固时间会随着过冷度的增大而逐渐降低。     

Pressure–volume–temperature behavior of nylon 610

Equilibrium pressure–volume–temperature behavior in both the solid and molten regions was determine for nylon 610. Data were measured with a compressibility device capable of obtaining precise and accurate data. Residual curve treatment showed that the data were true equilibrium data. A volume extrapolated to 2419 atm. at room temperature from the present data compared favorably to the sole literature value reported by Bridgman. The data of this work showed the existence of what appears to be a second-order transition point for nylon 610. This point ranged from 140°C. at 232 atm. to about 170°C. at 1855 atm. The Spencer-Gilmore equation was fitted to the data of this study.     

Knit lines structure in injection molding of nylon 6: Relation to first solidified sample cross section

The effect of processing variables on the knit line structure of nylon 6 samples was investigated. Either local sample thickening or grooves were observed at the knit lines for samples injected with mold conditioning temperatures of 130° and 30°C respectively. The results also indicate that shrinkage venting, either to or from the weld zone, is the dominant mechanism for knit line formation, which is thus related to the position where complete cross section solidification first takes place.     

Effect of solidification path on the microstructure of Al2O3–Y2O3–ZrO2 ternary oxide eutectic ceramic system

The solidification path of the Al₂O₃–Y₂O₃–ZrO₂ ternary oxide eutectic composite ceramic is determined by a high temperature DTA and laser floating zone (LFZ) directional solidification method to investigate the effect of solidification path on the microstructure of the ternary oxide. The DTA and microstructure analyses show that the YAG or Al₂O₃ tends to form as primary phase under the unconstrained solidification conditions, and then the system enters ternary eutectic solidification during cooling from 1950 °C at rate of 20 °C/min. The as-solidified composite ceramic shows a divorced irregular eutectic structure consisting of Al₂O₃, YAG and ZrO₂ phases with a random distribution. The primary phases are however completely restrained at the directional solidification conditions with high temperature gradient, and the ternary composite by LFZ presents well coupled eutectic growth with ultra-fine microstructure and directional array. Furthermore, the eutectic transformation and growth mechanism of the composite ceramic under different solidification conditions are discussed.     

Melting and solidification characteristics of confectionery fats: Anhydrous milk fat,cocoa butter and palm kernel stearin blends

Differential scanning calorimetry measurements of crystallization and melting characteristics of commercial samples of anhydrous milk fat (AMF), cocoa butter (CB) and hydrogenated palm kernel stearin (PKS) in ternary blends were studied. Results showed that stabilization at 26°C (either for 40 h or 7 d) did not greatly affect the melting thermogram trace of PKS. However, the effect of stabilization became prominent as CB was added into the system. Deviation of measured enthalpy from the corresponding values, calculated for thermodynamically ideal blends, showed clear interaction between all three fats. At 20°C, the strongest deviation occurred at about the AMF/CB/PKS (1∶1∶1) blend, whereas at 30°C the deviation moved toward the CB/MF (1∶1) blend. The presence of 25% AMF in PKS had little effect on its solidification capability, but solidification was adversely affected with inclusion of CB.     

Experimental Investigation of Performances of Microcapsule Phase Change Material for Thermal Energy Storage

Performances of microcapsule phase change material (MPCM) for thermal energy storage are investigated. The MPCM for thermal energy storage is prepared by a complex coacervation method with gelatin and acacia as wall materials and paraffin as core material in an emulsion system. A scanning electron microscope (SEM) was used to study the microstructure of the MPCM. In thermal analysis, a differential scanning calorimeter (DSC) was employed to determine the melting temperature, melting latent heat, solidification temperature, and solidification latent heat of the MPCM for thermal energy storage. The SEM micrograph indicates that the MPCM has been successfully synthesized and that the particle size of the MPCM is about 81 μm. The DSC output results show that the melting temperature of the MPCM is 52.05 °C, the melting latent heat is 141.03 kJ/kg, the solidification temperature is 59.68 °C, and the solidification latent heat is 121.59 kJ/kg. The results prove that the MPCM for thermal energy storage has a larger phase change latent heat and suitable phase change temperature, so it can be considered as an efficient thermal energy storage material for heat utilizing systems.