Download or read book Kinetics of Straininduced Crystallization of Polymers During Flow written by G. S. Y. Yeh and published by . This book was released on 1982 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results from experimental studies of strain-crystallized polyethylenes, prepared in a simple shear couette rheometer, indicate a substantial increase in nucleation rate, a decrease in long period, as well as an increase in melting temperature with increasing shear. The changes appear to have the same thermodynamic origin in the reduction of the amount of melt entropy, Delta S', just prior to crystallization according to a strain-induced crystallization theory by Yeh and Hong. Consequently from the measured nucleation rate one can predict what the decrease in long period or the increase in melting temperature should be for a given strain-crystallized polyethylene. For example, the measured melting temperatures are indeed shown to be comparable to those predicted from nucleation rate measurements.

Download or read book Flow Induced Crystallization of Polymers written by Gaetano Guerra and published by Wiley-VCH. This book was released on 2002-12-20 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt: In polymer processing, the molecular orientation induced by flow has a significant effect on the crystallization kinetics and final morphology of the polymer produced. The impact on processing operations and object properties is extremely important and recently scientific and technological researchers have begun to quanitify these effects. The international conference 'Flow-Induced Crystallization of Polymers', held in October 2001 in Salerno, Italy, was timely and well attended. An interdisciplinary approach was taken and presentations were made on topics ranging from real-time measurement, through modelling, to final morphology and properties of polymers. Invited and other selected contributions from the conference are collected here, in this volume of Macromolecular Symposia

Download or read book Mechanistic Kinetic Modeling of Flow induced Crystallization in Semi crystalline Polymers written by Lindsay Mendes and published by . This book was released on 1998 with total page 494 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Flow induced Crystallization in Polymer Systems written by Robert L. Miller and published by Taylor & Francis. This book was released on 1979-01-01 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Research in Progress written by and published by . This book was released on 1976 with total page 604 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book In situ Visualization and Quantification of Polymer Crystallization Under Complex Flows During Foam Extrusion Processing written by Alireza Tabatabaei Naeini and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The crystallization behavior of polypropylene (PP) and poly(lactic acid) (PLA) during foam extrusion processing was investigated via visualization techniques. In the experiments, a tandem extrusion system equipped with a conical converging flow channel and a high temperature/pressure visualization chamber were employed. Using the developed system, effect of processing parameters on crystallization was elucidated. These parameters included the processing temperature, the carbon dioxide content, the flow rate, and the strain rate. The visualized crystallites were quantified based on their light intensities and by the definition of the Crystallinity Index (CI) and the Crystallite Size (CS), where the CI and CS corresponded to the relative crystallinity and the size of crystallites, respectively. Moreover, a correlation was made between the content of the induced crystallites inside the extruder and the cellular structure of the extruded foams. It was verified by visualization that both PP and PLA crystallize during the process even at a temperature above their nominal melting peak point (Tm). The formation of crystallites at a temperature above the Tm was asserted to the strain-induced crystallization. Moreover, a procedure was proposed in order to decouple the effect of the flow rate (corresponded to the strain rate) and the cooling history. A significant enhancement in crystallization kinetics was observed by increasing the strain rate. This crystallization enhancement caused by the increased flow rate became more pronounced at lower temperatures, most probably due to the higher degree of molecular orientation. Adding the CO2 shifted the crystallization temperature to a lower processing temperature due to its plasticization effect, but it accelerated the crystallization kinetics. This clearly explained the decrease in the optimal processing temperature for foaming with an increased CO2 content. It was also confirmed that the induced crystallites during the process had a great effect on the cellular morphology of the resultant foam product.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 1572 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Crystallization in Multiphase Polymer Systems written by Sabu Thomas and published by Elsevier. This book was released on 2017-09-15 with total page 612 pages. Available in PDF, EPUB and Kindle. Book excerpt: Crystallization in Multiphase Polymer Systems is the first book that explains in depth the crystallization behavior of multiphase polymer systems. Polymeric structures are more complex in nature than other material structures due to their significant structural disorder. Most of the polymers used today are semicrystalline, and the subject of crystallization is still one of the major issues relating to the performance of semicrystalline polymers in the modern polymer industry. The study of the crystallization processes, crystalline morphologies and other phase transitions is of great significance for the understanding the structure-property relationships of these systems. Crystallization in block copolymers, miscible blends, immiscible blends, and polymer composites and nanocomposites is thoroughly discussed and represents the core coverage of this book. The book critically analyzes the kinetics of nucleation and growth process of the crystalline phases in multi-component polymer systems in different length scales, from macro to nanoscale. Various experimental techniques used for the characterization of polymer crystallization process are discussed. Written by experts in the field of polymer crystallization, this book is a unique source and enables professionals and students to understand crystallization behavior in multiphase polymer systems such as block copolymers, polymer blends, composites and nanocomposites. Covers crystallization of multiphase polymer systems, including copolymers, blends and nanocomposites Features comprehensive, detailed information about the basic research, practical applications and new developments for these polymeric materials Analyzes the kinetics of nucleation and growth process of the crystalline phases in multi-component polymer systems in different length scales, from macro to nanoscale

Download or read book Flow Induced Crystallization of Isotactic Polypropylene written by Benson Jacob and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flow-induced crystallization, ubiquitous in polymer melt processing techniques, occurs when semicrystalline polymer melts are subjected to large deformations prior to supercooling. The entropy-reduction and chain orientation involved in this process can form flow-induced precursors, which accelerate crystallization kinetics and transform the crystalline morphology. With increasing levels of shear stress, isotactic polypropylene can form a highly oriented structures, that result in improved material properties. The effect of particle concentration (catalyst residue) on the flow-induced crystallization of two samples of isotactic polypropylene was investigated through shear rheology and ex-situ simultaneous small/wide angle X-ray scattering (SAXS/WAXS). After the imposition of deformation, flow-induced crystallization was monitored in a rotational rheometer, where the sample with higher concentrations of catalyst residue showed faster crystallization kinetics and crystallized at higher temperatures. The effects of greater particle concentration diminished with increasing levels of specific work, where upon reaching a saturation threshold, particle nucleation was limited, and flow effects were predominant. At sufficiently large deformations, the highly oriented shish-kebab morphology could be induced when a critical shear stress of ~0.1 MPa is attained. Although typically linked to high levels of deformation, we also find that these shish-kebab structures can also be formed at low shear stresses when sheared for long times. We further quantify the effect of particle concentration in conditions of weak and strong flow to evaluate the flow-induced lamellar structure and orientation, where we observe that the spacing between adjacent lamella (long period) increases with shear stress.

Download or read book Crystallization Kinetics of Polymer Melts in Extensional Flow written by David Alan Tree and published by . This book was released on 1990 with total page 592 pages. Available in PDF, EPUB and Kindle. Book excerpt: A technique to study the kinetics of flow-induced crystallization of polymers in extensional flow has been developed which uses a 4-Roll Mill. The kinetics of a High Density Polyethylene were found to be well described by the Avrami treatment, indicated that the crystallization occurred by sporadic nucleation and one-dimensional growth and were a strong function of temperature and applied stress but were independent of strain history. The kinetics were found to be consistent with the Ziabicki theory for strain-induced crystallization but inconsistent with the theory of uttermost uniformity and an elevated melting point mechanism. The kinematics and stress fields of the 4-Roll Mill flow were measured independently by a tracer particle technique and an application of the Method of Isoclinics respectively allowing comparison to the predictions of several rheological equations of state. The deformation of a polymer droplet suspended in a carrier phase at low Reynolds number and high Weber number was documented. It is recommended that the 4-Roll Mill technique be used for study of other crystallizable polymer systems.

Download or read book Research in Progress Between and written by United States. Army Research Office and published by . This book was released on 1978 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heat Transfer in Polymer Composite Materials written by Nicolas Boyard and published by John Wiley & Sons. This book was released on 2016-03-03 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book addresses general information, good practices and examples about thermo-physical properties, thermo-kinetic and thermo-mechanical couplings, instrumentation in thermal science, thermal optimization and infrared radiation.

Download or read book Polymer Crystallization II written by Finizia Auriemma and published by Springer. This book was released on 2016-12-21 with total page 303 pages. Available in PDF, EPUB and Kindle. Book excerpt: The series Advances in Polymer Science presents critical reviews of the present and future trends in polymer and biopolymer science. It covers all areas of research in polymer and biopolymer science including chemistry, physical chemistry, physics, material science. The thematic volumes are addressed to scientists, whether at universities or in industry, who wish to keep abreast of the important advances in the covered topics. Advances in Polymer Science enjoys a longstanding tradition and good reputation in its community. Each volume is dedicated to a current topic, and each review critically surveys one aspect of that topic, to place it within the context of the volume. The volumes typically summarize the significant developments of the last 5 to 10 years and discuss them critically, presenting selected examples, explaining and illustrating the important principles, and bringing together many important references of primary literature. On that basis, future research directions in the area can be discussed. Advances in Polymer Science volumes thus are important references for every polymer scientist, as well as for other scientists interested in polymer science - as an introduction to a neighboring field, or as a compilation of detailed information for the specialist. Review articles for the individual volumes are invited by the volume editors. Single contributions can be specially commissioned. Readership: Polymer scientists, or scientists in related fields interested in polymer and biopolymer science, at universities or in industry, graduate students

Download or read book Principles of Polymer Systems Sixth Edition written by Ferdinand Rodriguez and published by CRC Press. This book was released on 2014-12-09 with total page 812 pages. Available in PDF, EPUB and Kindle. Book excerpt: Maintaining a balance between depth and breadth, the Sixth Edition of Principles of Polymer Systems continues to present an integrated approach to polymer science and engineering. A classic text in the field, the new edition offers a comprehensive exploration of polymers at a level geared toward upper-level undergraduates and beginning graduate students. Revisions to the sixth edition include: A more detailed discussion of crystallization kinetics, strain-induced crystallization, block copolymers, liquid crystal polymers, and gels New, powerful radical polymerization methods Additional polymerization process flow sheets and discussion of the polymerization of polystyrene and poly(vinyl chloride) New discussions on the elongational viscosity of polymers and coarse-grained bead-spring molecular and tube models Updated information on models and experimental results of rubber elasticity Expanded sections on fracture of glassy and semicrystalline polymers New sections on fracture of elastomers, diffusion in polymers, and membrane formation New coverage of polymers from renewable resources New section on X-ray methods and dielectric relaxation All chapters have been updated and out-of-date material removed. The text contains more theoretical background for some of the fundamental concepts pertaining to polymer structure and behavior, while also providing an up-to-date discussion of the latest developments in polymerization systems. Example problems in the text help students through step-by-step solutions and nearly 300 end-of-chapter problems, many new to this edition, reinforce the concepts presented.

Download or read book Rheo Physics of Multiphase Polymer Systems written by Kai Sondergaard and published by CRC Press. This book was released on 1995-06-02 with total page 604 pages. Available in PDF, EPUB and Kindle. Book excerpt: FROM THE PREFACE Almost all polymeric systems are subjected to a flow field at least once along the route between preparation and application. . . . There is also an increased interest in predictive models on phase behavior and suitable techniques for characterizing the structure of these systems when subjected to flow. Multiphase polymeric systems are particularly susceptible to flow, which may cause orientation of species, morphological changes, and phase transitions. All these events may, in turn, affect the end product properties, such as permeability, electrical conductivity, [and] mechanical properties. In processing, escalating needs have evolved for optimization and development of novel and more uniform product properties and increased productivity. In order to arrive at an understanding of processing polymeric systems under elastic flow conditions, it is convenient to analyze the basic physical mechanisms under conditions that enable development of predictive models in conjunction with controlled experimentation. . . . In recent years, the science of rheo-physics has evolved and now involves both advanced theories and experimental techniques. Rheo-physics means the rheological, morphological, and thermodynamic behavior of structured polymer systems during flow. . . . In this monograph, the rheo-optical techniques are . . . emphasized. The book gives an introduction to rheo-physics, including fundamentals of theories, and a representative selection of applications of rheo-optical techniques for analyzing multiphase systems. The chapters contain both practical advice for the new experimenter . . . as well as review material for the experienced scientist.

Download or read book Polymer Processing and Structure Relationships written by Domenico Acierno and published by John Wiley & Sons. This book was released on 2002-02-08 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: The rapid development of polymer technology in recent years has produced an increasing range of new polymers and additives, and seen much innovation in processing technologies. The need for understanding the relationships between polymeric structure, processing conditions and material properties is therefore greater than ever before. The EUROMAT 2001 conference held in June 2001 in Rimini, Italy was an ideal international forum for dealing with this complex subject. Selected lectures are presented in this volume of Macromolecular Symposia, which should be of interest to scientists of polymer chemistry and of polymer blending, processing and recycling, in academia and industry, alike.

Download or read book The Kinetics of Structure Development in Liquid Crystal Polymers written by Robert Clark Moore and published by . This book was released on 1986 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt: