1,851,522 research outputs found
Crystallization
No full textSince the first publication of this definitive work nearly 40 years ago, this fourth edition has been completely rewritten. Crystallization is used at some stage in nearly all process industries as a method of production, purification or recovery of solid materials. Incorporating all the recent developments and applications of crystallization technology, Crystallization gives clear accounts of the underlying principles, a review of the past and current research themes and guidelines for equipment and process design. This new edition introduces and enlarges upon such subjects as: · Control and Separation of polymorphs and chiral crystals · Micro- and macro-mixing and the use of computer fluid dynamics · Seeding and secondary nucleation in batch crystallization processes · Incorporation of upstream and downstream requirements into design procedures for crystallization plant · Computer-aided molecular design and its use in crystal habit modifier selection Crystallization provides a comprehensive overview of the subject and will prove invaluable to all chemical engineers and industrial chemists in the process industries as well as crystallization workers and students in industry and academia. Crystallization is written with the precision and clarity of style that is John Mullin's hallmark - a special feature being the large number of appendices that provide relevant physical property data. Covers all new developments and trends in crystallization. Comprehensive coverage of subject are
Crystallization kinetics of poly(lactic acid)-talc composites
Full text linkThe crystallization kinetics of Poly(lactic acid) / talc composites were determined over a range of 0 wt.% to 15 wt.% of talc. Talc was found to change the crystallization kinetics. The presence of talc increases the crystallization rate and this increase is related to talc concentration and to crystallization temperature. In order to understand the effect of talc and PLA crystallinity on mechanical properties, dynamic mechanical thermal analyses were performed on Poly(lactic acid) / talc composites before and after an annealing process. It was demonstrated that the presence of crystals improves thermo-mechanical properties but in order to achieve good results at high temperatures the reinforcing effect of a filler such as talc is necessar
Application of Two-Dimensional Correlation Analysis to Explosives Detection and Polymer Crystallization
Full text linkThis thesis presents two novel applications of two-dimensional (2D) correlation analysis: (1) long standoff detection of explosives and (2) morphology development in semicrystalline materials.
Due to the dangers of improvised explosive devices (IEDs), effective detection of explosives at standoff distances can save lives. A scheme based on 2D correlation analysis in conjunction with thermal modulation is proposed to overcome weak signals that plague long standoff detection. Implementation of 2D correlation analysis results in significant enhancement of explosive signals relative to background. Effective separation of explosive features resulting from their unstable nature compared to common contaminants is demonstrated for two biogenic compounds. Several aspects of 2D correlation analysis are examined to optimize effectiveness of detection.
Ultimate physical properties of semicrystalline materials are directly related to their morphology through molecular characteristics and processing conditions. The effects of different molecular characteristics on morphology of model hydrogenated polybutadienes are examined by 2D correlation analysis of x-ray scattering data.
Model short-chain branched (SCB) polyethylenes are found to crystallize in three regimes during quiescent temperature ramps. "Primary-irreversible" crystallization occurs at the highest temperatures as primary lamellae propagate through unconstrained melt. During "secondary-irreversible" crystallization at intermediate temperatures, secondary lamellae grow in the largest non-crystalline regions between primary lamellae. “Reversible” crystallization at low temperatures is marked by the formation of fringed micelles. This is the first time that a physical justification is presented for the separation of the irreversible crystallization into primary- and secondary-irreversible regimes.
Each regime is identified by unique features in 2D correlation plots. Two-dimensional correlation analysis provides unique insight into subtle changes in morphology, such as the development of density heterogeneities in non-crystalline regions.
The presence of short-chain branches is found to have a profound, diminishing effect on the formation of oriented structures in response to flow-induced crystallization, which is further examined through blends containing linear and SCB polyethylene. Evidence presented suggests that a buildup of chain defects at the growth front results in a transition from oriented to isotropic crystallization. It is proposed that size of crystal structures can be controlled by dictating the amount of copolymer incorporated during crystallization.</p
Secondary Crystallization of Isotactic Polystyrene
Full text linkWhen isotactic polystyrene (i-PS) is crystallized from the melt or from the glassy state at rather large supercooling an additional melting peak appears on the curve during scanning in a differential calorimeter. The overall rate of crystallization deduced from the total peak areas as a function of crystallization time did not fit the Avrami equation well. When we omit the area of the additional melting peak in the kinetic analysis a much better fit is obtained. We also observed that no lamellar thickening occurs during isothermal crystallization. In view of the low degree of crystallinity of i-PS these results lead to the idea that a secondary crystallization process takes place within the amorphous parts of the spherulites resulting in this additional melting peak on the DSC curve. The large supercooling needed and the increase in peak area with increasing molecular weight make us suppose that intercrystalline links are probably responsible for the additional melting peak of bulk-crystallized i-PS. Electron microscopic studies of surface replicas of i-PS support this view.
Self-interaction chromatography as a tool for optimizing conditions for membrane protein crystallization
Full text linkThe second virial coefficient, or B value, is a measurement of how well a protein interacts with itself in solution. These interactions can lead to protein crystallization or precipitation, depending on their strength, with a narrow range of B values (the `crystallization slot') being known to promote crystallization. A convenient method of determining the B value is by self-interaction chromatography. This paper describes how the light-harvesting complex 1-reaction centre core complex from Allochromatium vinosum yielded single straight-edged crystals after iterative cycles of self-interaction chromatography and crystallization. This process allowed the rapid screening of small molecules and detergents as crystallization additives. Here, a description is given of how self-interaction chromatography has been utilized to improve the crystallization conditions of a membrane protein
Handbook Of Industrial Crystallization
No full textCrystallization is an important separation and purification process used in industries ranging from bulk commodity chemicals to specialty chemicals and pharmaceuticals. In recent years, a number of environmental applications have also come to rely on crystallization in waste treatment and recycling processes. The authors provide an introduction to the field of newcomers and a reference to those involved in the various aspects of industrial crystallization. It is a complete volume covering all aspects of industrial crystallization, including material related to both fundamentals and applications. This new edition presents detailed material on crystallization of biomolecules, precipitation, impurity-crystal interactions, solubility, and design. Provides an ideal introduction for industrial crystallization newcomers Serves as a worthwhile reference to anyone involved in the field Covers all aspects of industrial crystallization in a single, complete volume.Includes bibliographical references and index.Solutions and solution properties / Albert M. Schwartz and Allan S. Myerson -- Crystals, crystal growth, and nucleation / Allan S. Myerson and Rajiv Ginde -- The influence of impurities and solvents on crystallization / Paul A. Meenan, Stephen R. Anderson, and Diana L. Klug -- Analysis and measurement of crystallization utilizing the population balance / K.A. Berglund -- Crystallizer selection and design / Richard C. Bennett -- Precipitation processes / P.H. Karpinski and J.S. Wey -- Melt crystallization / J. Ulrich and H.C. Bülau -- Crystallizer mixing : understanding and modeling crystallizer mixing and suspension flow / Daniel Green -- Control of crystallization processes / J.B. Rawlings, C.W. Sink, and S.M. Miller -- Batch crystallization / J.S. Wey and P.H. Karpinski -- Crystallization in the pharmaceutical and bioprocessing industries / D.J. Kirwan and C.J. Orella -- Crystallization of proteins / John Wiencek -- Crystallization in foods / Richard W. Hartel.Print version record.Crystallization is an important separation and purification process used in industries ranging from bulk commodity chemicals to specialty chemicals and pharmaceuticals. In recent years, a number of environmental applications have also come to rely on crystallization in waste treatment and recycling processes. The authors provide an introduction to the field of newcomers and a reference to those involved in the various aspects of industrial crystallization. It is a complete volume covering all aspects of industrial crystallization, including material related to both fundamentals and applications. This new edition presents detailed material on crystallization of biomolecules, precipitation, impurity-crystal interactions, solubility, and design. Provides an ideal introduction for industrial crystallization newcomers Serves as a worthwhile reference to anyone involved in the field Covers all aspects of industrial crystallization in a single, complete volume.Elsevie
Crystallization of Niobium Containing Bioactive Phosphate Glass
No full textCrystallization of niobium containing bioactive phosphate glas
Phosphorus recovery from wastewater by struvite crystallization: A review
Full text linkThe present review provides an understanding of principles of struvite crystallization and examines the techniques and processes experimented to date by researchers at laboratory, pilot, and full-scale to maximize phosphorus removal and reuse as struvite from wastewater effluents. Struvite is mainly known as a scale deposit causing concerns to wastewater companies. Indeed, struvite naturally occurs under the specific condition of pH and mixing energy in specific areas of wastewater treatment plants (e.g., pipes, heat exchangers) when concentrations of magnesium, phosphate, and ammonium approach an equimolar ratio 1:1:1. However, thanks to struvite composition and its fertilizing properties, the control of its precipitation could contribute to the reduction of phosphorus levels in effluents while simultaneously generate a valuable by-product. A number of processes such as stirred tank reactors and air-agitated and -fluidized bed reactors have been investigated as possible configurations for struvite recovery. Fluidized bed reactors emerged as one of the promising solutions for removing and recovering phosphorus as struvite. Phosphorus removal can easily reach 70% or more, although the technique still needs improvement with regard to controlling struvite production quality and quantity to become broadly established as a standard treatment for wastewater companies
Distinct Crystallization Pathways of Polyoxymethylene in Methanol System
No full textRecrystallization of polyoxymethylene (POM) in solvent is an effective post-treatment method for manufacturing a better POM product. Herein, the crystallization process of POM in methanol was investigated with the use of a series of equipment. The results reveal that POM crystallization in methanol yields two kinds of particle morphologies, including small particles with lamellar structures branching and growing in all directions and large particles resulting from melt agglomeration. The mechanism of POM crystallization in methanol with two distinct pathways was proposed, in which solution cooling crystallization of POM at higher temperature yields small particles while melt crystallization yields large particles. Furthermore, both non-isothermal and isothermal crystallization kinetics of POM were determined. The Avrami equation was employed to derive the crystallization rate constant via data fitting. The activation energy of crystallization was then obtained using the Arrhenius formula. The kinetics suggest that recrystallization of POM in methanol may dissolve and remove substances hindering raw material crystallization, achieving a faster crystallization rate for products
Crystallization behavior of poly(lactide)/poly(β-hydroxybutyrate)/talc composites.
Full text linkThe authors thank Dr. Patrice Lefrançois (CNAM) for SEM observations. They are also grateful to Pr. Jack R. Plimmer USDA, Agricultural Research Service, USA for his discussions during this work.The morphology and miscibility of commercial poly(lactide) (PLA)/poly(b-hydroxybutyrate) (PHB, from 5 to 20 wt %) blends prepared by melt extrusion method, were investigated using differential scanning calorimetry (DSC) and Fourier transform infra-red spectroscopy (FTIR) observations. The results show that for all the studied blend contents, PLA/PHB blends are immiscible. The effects of PHB and talc on the nonisothermal cold crystallization kinetics of PLA were examined using a differential scanning calorimetry (DSC) at different heating rates. PHB acted as a nucleating agent on PLA and the addition of talc to the blend yielded further improve-ment, since significant increase in the enthalpy peak was observed for samples containing 10 wt % PHB and talc (from 0.5 to 5 phr). The crystallization kinetics were then examined using the Avrami–Jeziorny and Liu–Mo approach. The simultaneous presence of PHB and talc induced a decrease of the crystallization half time. The evolution of activation energies determined with Kissinger’s equation suggests that blending with PHB and incorporating talc promote nonisothermal cold crystallization of PLA. The synergistic nucleating effect of PHB and talc was also observed on isothermal crystallization of PLA from the melt
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