SOME PROPERTIES OF ZINC OXIDE BODIES1

Melting Point of ZnO .—The melting point of ZnO is above 1800° C and may be above its normal sublimation point. Volume Shrinkage and Porosity of ZnO Bodies .—A very hard and dense body composed of pure ZnO can be prepared. At high temperatures it exhibits the unusual phenomenon of volume shrinkage accompanied by an increasing porosity. Zinc Retort Bodies .—In the discussion the possible advantages of incorporating zinc oxide in a zinc retort body are mentioned.     

Using X‐Ray Microtomography for Characterisation of Catalyst Particle Pore Structure

The use of a high‐energy synchrotron radiation source has permitted the introduction of high‐resolution X‐ray microtomography imaging as a method of non‐intrusive and non‐destructive three‐dimensional (3D)visualized characterization of porous media. The use of a combination of X‐ray microtomography, along with mercury porosimetry and Low Melting Point Alloy (LMPA) intrusion potentially provides a more complete approach to more accurate catalyst pore structure characterisation and modelling. This combined approach has been applied to the study of an industrial alumina catalysts support. The data collected from the study has been used to develop and generate an improved pore network model basis, in which both heterogeneity and hierarchy are considered in obtaining an improved pore architecture and pore size distribution.     

四氢β-咔啉氧化条件探讨

分别采用KMnO4、S/二甲苯、H2O2/乙酸酐和Pd/C四种不同的脱氢氧化条件从四氢β-咔啉合成β-咔啉;文章探讨了各种氧化条件下的产率和工业合成的可行性,并比较了S在不同溶剂的氧化收率和实用性;采用熔点测定、红外光谱、核磁共振光谱等方法对目标产物进行表征。得到氧化的最佳条件是以S/二甲苯为氧化剂,反应8h,收率为56.1%。     

Melting point,solidification, and consistency

Summary There are probably as many methods or variations of methods for melting points, solidification, and consistency as there are producers in the fats and oil industry. I have tried to review the more important ones. The interpretation of results and importance attached to each test will vary widely from producer to producer. My presentation and interpretation have been primarily of methods used by our company and related to the shortening field. In our experience the data obtained from Wiley Melting Points, Penetration Values, and % solids from dilations are the primary controls for the consistency of our products.     

Modification of cyclohexanone–formaldehyde resins with silicone tegomers

Cyclohexanone–formaldehyde resins were modified in situ with α,ω‐diamine polydimethylsiloxanes and α,ω‐dihydroxy polydimethylsiloxanes. Melting points, solubilities in organic solvents, gel permeation chromatographs, Fourier transform infrared spectra, and NMR spectra of the modified resin were determined, and the surface properties of the resins were investigated by contact angle measurements. A small amount of silicon compounds seemed to effect the physical properties of the cyclohexanone–formaldehyde resins significantly. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 97–101, 2005     

Correlation of properties with structure in ziegler polypropylenes

Isotactic polypropylenes, varying in molecular weight, crystallinity, and tacticity, were characterized by spectroscopic and chromatographic techniques in order to obtain suitable samples for investigating the effect of structure on properties. Mechanical and thermal properties were studied with respect to their structural dependence. Melting points and rates of crystallization were observed to be higher in the more stereoregular samples, while evidence of fractionation by molecular weight and tacticity was observed in less stereoregular samples. Tensile properties displayed marked dependence on polymer stereoregularity, while examination of fractured surfaces by microscopy showed that fracture occurred at regions of high impurity concentration. © 1992 John Wiley & Sons, Inc.     

Crystallization and melting of highly filled polypropylene composites prepared with surface‐treated fillers

Polypropylene (PP) composites with high filler content have been prepared with surface‐treated fillers. The effect of the filler is twofold; nucleation of crystallization occurs, though the PP is also adsorbed onto the filler thereby retarding its motion. Differential scanning calorimetry has been used to study the crystallization of the PP. Melting and recrystallization during melting has been characterized by differential scanning calorimetry. The properties of the composites are more than an additive combination of the filler and polymer. In the case of highly filled composites, the morphology of the PP is important in limiting brittleness and for the strength of the interface between filler and polymer. Surface treatment of the filler has been found to have a significant control over the morphology and properties of the composites. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1942–1948, 2001     

Influence of gamma-irradiation on structural and mechanical properties of polypropylene yarn

Polypropylene multifilament yarn samples were irradiated by gamma rays in air. The effect of radiation dose on thermal, structural, and mechanical properties was studied. Melting endotherms and crystallization exotherms gave useful information regarding the structural changes. X-ray diffraction, infrared spectroscopy, density, and viscosity data of the irradiated samples were analyzed. Although viscosity and mechanical properties decreased with irradiation, the density marginally increased. Breaking elongation has been found be a sensitive parameter for assessing deterioration. © 1995 John Wiley & Sons, Inc.     

Thermal memory of polyethylenes analyzed by temperature modulated differential scanning calorimetry

Temperature modulated differential scanning calorimetry (TMDSC) was employed to study the melting and crystallization behavior of various polyethylenes (PEs). Samples of high density PE (HDPE), low density PE (LDPE), linear low density PE (LLDPE), and very low density PE (VLDPE) with different crystal structures and morphologies were prepared by various thermal treatments (isothermal crystallization and slow, fast, and dynamic cooling). The reversing and nonreversing contributions, measured on the experimental time scale, were varied, depending on the crystal stability. A relatively large reversing melt contribution occurs for unstable crystals formed by fast cooling compared to those from slow cooling treatments. All samples of highly branched LDPE, LLDPE, and VLDPE showed a broad exotherm before the main melting peak in the nonreversing curve, suggesting crystallization and annealing of crystals to more stable forms. Other samples of HDPE, except when cooled quickly, did not show any significant crystallization and annealing before melting. The crystallinity indicated that dynamically cooled polymers were much more crystalline, which can be attributed to crystal perfection at the lamellar surface. A reversible melting component was also detected during the quasiisothermal TMDSC measurements. Melting is often accompanied by large irreversible effects, such as crystallization and annealing, where the crystals are not at equilibrium. Such phenomena during a TMDSC scan provide information on the polymer thermal history. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 681–692, 2003     

Miscibility and processibility in linear low density polyethylene and ethylene-propylene-butene-1 terpolymer binary blends

Blends of linear low density polyethylene (ethylene-octene-1 copolymer) and ethylene-propylene-butene-1 terpolymer (ter-PP) mixed in a twin-screw extruder have been characterized by using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis, scanning electron microscopy (SEM), rheometric mechanical spectrometry, a capillary rheometer, and a universal test machine. Melting and crystallization behaviors by DSC and the α, β, and γ dynamic mechanical relaxations proposed that the blend is immiscible in the amorphous and crystalline phases by observing the characteristic peaks arised solely from those of the constituents. The lack of interfacial interaction between the components was suggested by the SEM study. A strong negative deviation of melt viscosity from the additive rule and the Cole-Cole plot confirmed the immiscibility in melt state. Incorporation of ter-PP induced a reduction in melt viscosity, shear stress, and final load. Flexural modulus and yield stress were linearly increased with ter-PP content, while the tensile strength and elongation at break were more or less changed. Although this blend system is immiscible in the solid and melt states, addition of less than 20 wt % ter-PP in the blend is viable for engineering applications with the advantages of improved processibility and mechanical properties. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1265–1274, 1997     

AN EXPERIMENTAL STUDY OF MELTING VERTICAL ICE CYLINDERS IN COLD WATER

Short vertical ice cylinders were melted in quiescent ambient cold fresh water to visualize the melting and the resulting convective motions. Melting rates and heat transfer parameters were also determined. The cylinder penetrated the water surface, to model the melting of floating surface ice. Melting experiments over the ambient medium temperature range, t ∞, from 2 to 7°C covered the whole gamut of differing and complicated effects found to be associated with the occurance of a density extremum. At t ∞ = 2°C, simple general upflow is found, at t ∞ = 7°C simple downflow. Between these two limits, three different and much more complicated regimes arose. Buoyancy force reversal arises first, with increasing t ∞, at about 4°C. Then local flow reversal follows, in the range to about 5.3°C. Finally a convective inversion, that is, an average flow reversal, occurs. A tremendous variation of flow pattern occurs over a range of only a few degrees. Melting rates become very low in the region of inversion. This was also found in previous measurements with the simpler flows which occur adjacent to thin and completely submerged vertical ice slabs. However, many flow and transport effects were quite different, with a flat bottom surface and with the ice-water-air interface. Three flows of different configurations interact. It appears that the realistic modelling of the melting of multidimensional pieces of surface ice will require a composite of the different characteristics of these multiple regions.     

Modification of acetophenone–formaldehyde and cyclohexanone–formaldehyde resins

Cyclohexanone–formaldehyde and acetophenone–formaldehyde resin were in situ modified with phenol, Bisphenols, and substituted acetophenones. Furthermore, acetophenone–formaldehyde, cyclohexanon–formaldehyde, and in situ-modified resins were modified with anhydrides such as acetic anhydride, maleic anhydride, dodecenylsuccinic anhydride, 3,4,3′,4′-biphenyltetracarboxylic dianhydride, and 4,4′-oxydiphtalic anhydride. Modification of these resins with hydroxyl amine, semicarbazide, and phenyl hydrazine were also studied. Melting points, solubilities in organic solvents, FTIR, and NMR spectrum of the modified resins were determined. © 1996 John Wiley & Sons, Inc.     

Increasing solvent polarity and addition of salts promote β‐phase poly(vinylidene fluoride) formation

This article investigates the effects of solvent polarity and salt addition on β‐phase poly(vinylidene fluoride) (PVDF) formation. Films were solvent cast in aprotic solvents of varying polarities with or without salt addition. Characterization was done by Fourier transformed infra‐red spectroscopy, differential scanning calorimetry, and scanning electron microscopy. Decreasing fractions of β‐phase PVDF was observed with increasing drying temperature when less polar solvents were used. The most polar solvent (hexamethylphosphoramide) consistently produced films with at least 90.0% β‐phase PVDF within the crystalline regions. Melting temperatures increased in correlation to absolute proportions of β‐phase PVDF. Salt addition increased the formation of β‐phase PVDF by 30%, with salts of higher valencies and smaller ionic radii resulting in more significant increases. Taken collectively, using solvents of higher polarities and addition of salts with high cationic valencies and small ionic radii will maximize β‐phase formation in solvent cast PVDF films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

AN EXPERIMENTAL STUDY OF MELTING VERTICAL ICE CYLINDERS IN COLD WATER

Short vertical ice cylinders were melted in quiescent ambient cold fresh water to visualize the melting and the resulting convective motions. Melting rates and heat transfer parameters were also determined. The cylinder penetrated the water surface, to model the melting of floating surface ice. Melting experiments over the ambient medium temperature range, t ∞, from 2 to 7°C covered the whole gamut of differing and complicated effects found to be associated with the occurance of a density extremum. At t ∞ = 2°C, simple general upflow is found, at t ∞ = 7°C simple downflow. Between these two limits, three different and much more complicated regimes arose. Buoyancy force reversal arises first, with increasing t ∞, at about 4°C. Then local flow reversal follows, in the range to about 5.3°C. Finally a convective inversion, that is, an average flow reversal, occurs. A tremendous variation of flow pattern occurs over a range of only a few degrees. Melting rates become very low in the region of inversion. This was also found in previous measurements with the simpler flows which occur adjacent to thin and completely submerged vertical ice slabs. However, many flow and transport effects were quite different, with a flat bottom surface and with the ice-water-air interface. Three flows of different configurations interact. It appears that the realistic modelling of the melting of multidimensional pieces of surface ice will require a composite of the different characteristics of these multiple regions.     

中频炉熔配法冶炼稀土硅钡钙镁合金

本文叙述了在中频炉中用硅钡铁、硅铁、稀土镁合金、镁锭、生铁、钙屑等原料通过熔配法冶炼稀土硅钡钙镁合金的试验过程。实践证明,用中频炉熔配法作为冶炼该合金,工艺上具有可行性,成分易于调配,镁的加入采用冲镁法是可行的方法,但是烧损率大,镁的加入采用完全熔配法可减少烧损,但必须解决熔配法的喷溅问题。     

Kinetic expression for the isothermal crystallization of poly(3‐hydroxybutyrate)–11%poly(3‐hydroxyvalerate)

The use of polyhydroxyalkanoates as a biodegradable semicrystalline polymer is currently increasing. The prediction of crystallinity profiles produced in part with this polymer requires the knowledge of the kinetic expression. In the present article, a kinetic expression of the isothermal melt crystallization of poly(3‐hydroxybutyrate)–11%poly(3‐hydroxyvalerate) [P(HB‐co‐11%HV)] was studied in two temperature ranges, close to the melting point and close to the glass transition. Melting behavior and molecular mobility of the amorphous phase were analyzed as a function of crystallization temperatures by performing calorimetric experiments. The Avrami equation was used and the activation energy of the crystal nucleation and growth were obtained. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1657–1661, 2004     

Synthesis,thermal, and photo alignment behavior of polyethylene imines having nitro substituent azobenzene side chain group

Polyethylene imines having nitro substituent azobenzene side chain group with different methylene spacer groups (PEImN) were successfully synthesized and characterized by differential scanning calorimetry, polarized optical microscopic, and X‐ray diffraction analysis. All synthesized polyethylene imines showed liquid crystalline properties and the glass transition temperature (Tg) of PEImN decreased as the number of methylene spacers increased. Melting temperatures (Tm) of synthesized PEImN showed an odd‐even effect. Photochemical, thermo‐optical, as well as photo alignment behavior of PEImN were investigated and out‐of‐plane orientational behavior of polymeric films was dependent on number of methylene spacers and polyethylene imines having higher number of methylene spacers (six or more) showed high order parameter values that revealed the well pronounced tendency for the development of out‐of‐plane order from random state on annealing. And the molecular orientation of PEImN between random and out‐of‐plane structures has been achieved by the combination of thermal and photochemical processes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Melting behavior,isothermal and nonisothermal crystallization kinetics of PP/mLLDPE blends

Melting behavior, nonisothermal crystallization and isothermal crystallization kinetics of polypropylene (PP) with metallocene‐catalyzed linear low density polyethylene (mLLDPE) were studied by differential scanning calorimetry (DSC). The results show that PP and mLLDPE were partially miscible. The Avrami analysis was applied to analyze the nonisothermal and isothermal crystallization kinetics of the blends, the Mo Z.S. method was used to take a comparison in nonisothermal kinetics. Values of Avrami exponent indicate the crystallization nucleations of both pure PP and PP in the blends were heterogeneous, the growth of spherulites is tridimensional and the spherulites in the blends were more perfect than that in pure PP. The crystallization activation energy was estimated by Kissinger method and Arrhenius equation and the two methods draw similar results. The mLLDPE increased the crystallization rate of PP in nonisothermal crystallization process and decreased it in isothermal process. The results from nonisothermal crystallization and isothermal crystallization kinetics were not consistent because the two processes were completely different. Addition of minor mLLDPE phase favors to increase the overall crystallinity of PP, showing the mLLDPE entered the PP crystals. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of processing on the microstructure,melting behavior,and equilibrium melting temperature of polypropylene

Polypropylene (PP) was extruded and injection-molded several times to mimic the effect of recycling procedures on PP. Differential scanning calorimetry (DSC) was used to follow crystallization rates under isothermal conditions in a temperature range of 120–150°C. Melting behavior and equilibrium melting temperatures were studied using the Hoffman-Weeks method of extrapolation. Optical microscopy combined with a hot stage was also used to follow the spherulite microstructure and crystal phase upon recycling of PP. Wide-angle X-ray spectroscopy identified the crystal phase at different isothermal crystallization temperatures. Twin melting peaks obtained for PP melting following isothermal crystallization were associated with crystal rearrangement during fusion. PP spherulite size and equilibrium melting temperatures were seen to increase with processing events, whereas reprocessing decreased nuclei density. © 1996 John Wiley & Sons, Inc.     

Die Kinetik des Schmelzens und der Kristallisation von Kakaobutter

The Kinetics of Melting and Crystallization of Cocoa Butter Melting is kinetically the reverse of crystallization. It was shown in a previous publication that the kinetics of fat crystallization is the same as that of precipitation from colloids. It is shown in the present paper that the kinetics of melting of solid fat is the same as that of the dispersion of gels. The kinetics of the melting of cocoa butter was investigated by linearization of experimental data from the literature. The linearization shows that the melting is accompanied by crystal transformations, and that the various crystal forms melt in succession.