Download or read book Extensional flow induced Crystallization of Polypropylene written by Erica E. Bischoff White and published by . This book was released on 2011 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: A filament stretching extensional rheometer was used to investigate the effect of uniaxial flow on the crystallization of polypropylene. Samples were heated to a temperature above the melt temperature to erase their thermal and mechanical histories. The Janeschitz-Kriegl protocol was applied and samples were stretched at various extension rates to a final strain of e = 3.0. Differential scanning calorimetry was applied to crystallized samples to measure the degree of crystallinity. The results showed that a minimum extension rate, corresponding to a Weissenberg number of approximately Wi = 1, is required for an increase in percent crystallization to occur. Below this Weissenberg number, the flow is not strong enough to align the tubes of constrained polymer chains and as a result there is no change in the final percent crystallization. An extension rate was also found for which percent crystallization is maximized. The increase in crystallinity is likely due to flow-induced orientation and alignment of tubes of constrained polymer chains. Polarized-light microscopy verified an increase in number and decrease in size of spherulites with increasing extension rate. Small angle X-ray scattering showed a 7% decrease in inter-lamellar spacing at the transition to flow-induced increase in crystallization. Crystallization kinetics were examined by observing the time required for melts to crystallize under uniaxial flow. The crystallization time decreased with increasing extension rate, even for extension rates where no increase in percent crystallization was observed. These results demonstrate that the speed of crystallization kinetics is greatly enhanced by the application of extensional flow.

Download or read book Extensional Flow Induced Crystallization of Polyethylene written by Anthony Joseph McHugh and published by . This book was released on 1972 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Extensional Flow Induced Crystallization in Polyethylene Melt Spinning written by Vikas Madhusudan Nadkarni and published by . This book was released on 1974 with total page 736 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Factors Affecting Extensional Flow induced Crystallization in High Density Polyethylene written by Sheena Jacob and published by . This book was released on 2000 with total page 526 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Molecular Aspects of Flow induced Crystallization of Polypropylene written by Derek Wade Thurman and published by . This book was released on 2006 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Influence of the Temperature on Flow induced Crystallization of Isotactic Polypropylene and Propylene ethylene Random Copolymer written by Hugo Boitout and published by . This book was released on 2014 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt: When flow is applied on a semi-crystalline polymer melt, it can greatly impact how it crystallizes its final properties. Therefore, it is crucial to understand the basic mechanism of flow induced crystallization (FIC). Only then will it be possible to predict final properties from the type of resin and processing conditions. Polypropylene is one of the most widely used polymers. Its processing generally involves subjecting the melt to intense flow fields, so FIC commonly occurs. This study investigates the influence of temperature of shear and crystallization on the FIC behavior of isotactic polypropylene (iPP). Temperature is one of the main controlled parameters in processing techniques such as injection and extrusion. Here, iPP is subjected to a range of shear stresses and shearing times at three different temperatures. Optical polarized microscopy displays differences in the morphology that forms after FIC at different temperatures. Real-time in-situ optical measurements track structure formation during and after shear. Capillary rheometry reveals changes in the rheological behavior of the polymer melt during flow. Finally, a depth-sectioning method is used to isolate the contribution to FIC of each sample layer at the different temperatures investigated. It was found that temperature has a significant influence on how oriented structures form: the formation of a highly-oriented skin is facilitated at low temperature in terms of required critical shear stress. However, the boundary between the highly oriented skin and other types of morphologies is not as sharp as at higher temperatures due to the presence of other oriented structures (skin lines and sausages). Results also indicate that, at low temperature, the rapid rate of growth of kebabs already during the shear pulse can impact the formation of oriented precursors under strong flow conditions. Generally, the observed trends suggest that the effects of increasing temperature are comparable to the effects of increasing the ethylene content in a random copolymer of iPP previously observed in a prior study.

Download or read book Theory and Methods Toward an Understanding of Flow induced Crystallization of Isotactic Polypropylene written by Michael P. Howard and published by . This book was released on 2013 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Flow induced Crystallization in Isotactic Polypropylene written by Fawzi Hamad and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Brief intervals of strong flow stretch chains in a semicrystalline polymer melt, which results in an increase in the nuclei number density and a transformation of the crystal structure. This flow-induced crystallization (FIC) phenomenon is explored in this study using highly isotactic polypropylene (iPP) samples. Using one synthesized and five commercial linear isotactic polypropylene samples, we investigate the FIC behavior by imposing shear onto these samples in a rotational rheometer. Equipped with a good temperature control and flexible shear protocol, we apply different temperature and flow conditions. The magnitude of the FIC effect varies with basic processing parameters (shear rate, specific work, crystallization temperature, and shearing temperature) and material properties (tacticity, molecular weight distribution, and particle concentration in the polymer). The scope of this study is to systematically investigate the influences of these parameters on FIC. The FIC effects that are investigated in this dissertation are: crystallization kinetics, persistence time of flow-induced nuclei, and crystal morphology. The crystallization time was measured in the rheometer by monitoring the onset of crystallization after quenching samples sheared above Tm. These samples were subsequently used to study their flow-induced nuclei persistence time and crystal morphology. The lifetime of flow-induced nuclei was determined by measuring the time required to return from FIC back to quiescent crystallization using a differential scanning calorimeter. The crystal morphology was imaged using polarized optical microscopy and atomic force microscopy. We investigated the influence of specific work on the three FIC characteristics, and found three regimes that are separated by the critical work (Wc) and the saturation work (Wsat) thresholds. Below the critical work threshold, the morphology is composed of mostly spherulite crystals, which keep a constant volume, and a small fraction of rice grain (anisotropic) crystals. The number of rice grain crystals increases with specific work, speeding up the crystallization time of the semicrystalline polymer. At critical work, spherulite formation stops, and the morphology consists only of rice grain structures. This morphology allows the sample to crystallize at higher temperatures when cooling at 5 C/min, with the sheared sample crystallizing at 129C compared to the unsheared sample at 113C. In addition, these rice grain structures can withstand significant annealing at elevated temperatures: for example, 2 days of annealing at 210C are required to fully erase these metastable nuclei. For Wc W

Download or read book An Experimental Study of Flow induced Crystallization in High Density Polyethylene and Polypropylene written by Madhav Kakani and published by . This book was released on 1997 with total page 340 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 Shear Induced Crystallization of Polypropylene Melts written by Michael John Keaton and published by . This book was released on 1970 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 Polypropylene written by J. Karger-Kocsis and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 988 pages. Available in PDF, EPUB and Kindle. Book excerpt: My heart sank when I was approached by Dr Hastings and by Professor Briggs (Senior Editor of Materials Science and Technology and Series Editor of Polymer Science and Technology Series at Chapman & Hall, respectively) to edit a book with the provisional title Handbook of Poly propylene. My reluctance was due to the fact that my former book [1] along with that of Moore [2], issued in the meantime, seemed to cover the information demand on polypropylene and related systems. Encour aged, however, by some colleagues (the new generation of scientists and engineers needs a good reference book with easy information retrieval, and the development with metallocene catalysts deserves a new update!), I started on this venture. Having some experience with polypropylene systems and being aware of the current literature, it was easy to settle the titles for the book chapters and also to select and approach the most suitable potential contributors. Fortunately, many of my first-choice authors accepted the invitation to contribute. Like all editors of multi-author volumes, I recognize that obtaining contributors follows an S-type curve of asymptotic saturation when the number of willing contributors is plotted as a function of time. The saturation point is, however, never reached and as a consequence, Dear Reader, you will also find some topics of some relevance which are not explicitly treated in this book (but, believe me, I have considered them).

Download or read book Flow induced crystallization of polymers Impact to processing and manufact properties written by Giuseppe Titomanlio and published by . This book was released on 2001 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Crystallization Modalities in Polymer Melt Processing written by Hermann Janeschitz-Kriegl and published by Springer Science & Business Media. This book was released on 2009-09-18 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: Structure formation in crystallizing polymers, as occurring during processing, has not been treated so far in a coherent form. This fact explains, why this monograph is written as the ?rst book devoted to this subject. A quarter of a century ago the underdevelopment of this subject was obvious. Trial and error dominated. In fact, other apposite subjects as polymer melt rheology or heat transfer, had reached high levels. A great number of books has been devoted to them. Mold ?lling of amorphous polymers and the solidi?cation of these polymers by vitri?cation can nowadays be simulated numerically with a high degree of accuracy. In the solidi?ed sample even residual stresses and corresponding birefringence effects can accurately be 1 calculated . However, semicrystalline polymers, which form the majority of industrial po- mers, have been excluded from these considerations for good reasons. In fact, great uncertainties existed about the formation of quality determining crystalline str- tures. In particular, polyole?ns suffered from this shortcoming. In 1983 this fact instigated the polymer research group at the Johannes Kepler University in Linz to start with pertinent activities. The urgency of this kind of studies becomes evident, if advantages and hitches of these polymers are considered. 1. Versatility of processing: Injection molding into a great variety of shapes and sizes, from thin walled beakers to garden chairs, not to forget pipe and pro?le extrusion, cable coating, ?ber spinning, ?lm blowing. 2. Product qualities: Ductility, low density, good electric insulation, corrosion resistance, surface quality.