Processing, Structure and Property Relationships in Commercial Thermotropic Liquid Crystalline Polymers PDF Download
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Author: Stanley Rendon
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Thermotropic liquid crystalline polymers (TLCPs) offer considerable promise as high strength/lightweight engineering materials. Their excellent mechanical properties are derived from the spontaneous ordering of stiff polymer molecules in the melt state, which is ultimately translated into high molecular orientation in finished products. Understanding the effect of processing on molecular orientation, and specifically the role and mechanisms by which flow fields impact molecular orientation, is thus a prerequisite to rational design of processes that exploit and enhance the characteristics of TLCPs. The lack of fundamental knowledge to rationally anticipate structure development during processing of commercial main-chain TLCPs however, has significantly hindered the wide spread applicability of these materials. In light of the need for improved understanding of flow-orientation relationships in TLCPs, this thesis presents the first coordinated attempt to combine fundamental studies of orientation development in well-defined simple flows (simple shear) and complex processing flows (extrusion and injection molding) using in situ x-ray scattering methods, with structure and property investigations of injection molded plaques made from commercial TLCPs.
Author: Stanley Rendon
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Thermotropic liquid crystalline polymers (TLCPs) offer considerable promise as high strength/lightweight engineering materials. Their excellent mechanical properties are derived from the spontaneous ordering of stiff polymer molecules in the melt state, which is ultimately translated into high molecular orientation in finished products. Understanding the effect of processing on molecular orientation, and specifically the role and mechanisms by which flow fields impact molecular orientation, is thus a prerequisite to rational design of processes that exploit and enhance the characteristics of TLCPs. The lack of fundamental knowledge to rationally anticipate structure development during processing of commercial main-chain TLCPs however, has significantly hindered the wide spread applicability of these materials. In light of the need for improved understanding of flow-orientation relationships in TLCPs, this thesis presents the first coordinated attempt to combine fundamental studies of orientation development in well-defined simple flows (simple shear) and complex processing flows (extrusion and injection molding) using in situ x-ray scattering methods, with structure and property investigations of injection molded plaques made from commercial TLCPs.
Author: T. Kajiyama
Publisher:
ISBN:
Category :
Languages : en
Pages : 16
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Book Description
Author: Domenico Acierno
Publisher: Springer Science & Business Media
ISBN: 940091511X
Category : Technology & Engineering
Languages : en
Pages : 331
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Book Description
Liquid crystal polymers (LCPs) have many strange properties that may be utilized to advantage in the processing of products made from them and their blends with isotropic polymers. This volume (volume 2 in the series Polymer Liquid Crystals) deals with their strange flow behaviour and the models put forward to explain the phenomena that occur in such polymers and their blends. It has been known for some time that small ad ditions of a thermotropic LCP to isotropic polymers not only gives an improvement in the strength and stiffness of the blend but improves the processability of the blend over that of the isotropic polymer. In the case of lyotropic LCPs, it is possible to create a molecular composite in which the reinforcement of an isotropic polymer is achieved at a molecular level by the addition of the LCP in a common solvent. If the phenomena can be fully understood both the reinforcement and an increase in the proces sability of isotropic polymers could be optimized. This book is intended to illustrate the current theories associated with the flow of LCPs and their blends in the hope that such an optimization will be achieved by future research. Chapter 1 introduces the subject of LCPs and describes the ter minology used; Chapter 2 then discusses the more complex phenomena associated with these materials. In Chapter 3, the way in which these phe nomena may be modelled using hamiltonians is fully covered.
Author: Domenico Acierno
Publisher: ChemTec Publishing
ISBN: 1895198046
Category : Crystalline polymers
Languages : en
Pages : 227
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Book Description
Some papers in this book report on the most recent developments in pure liquid crystalline polymers showing that discipline is dynamic and may offer in the future numerous other opportunities not known today. We hope that our selections of papers will be interesting for specialists in polymer chemistry, blends, and their industrial application, and that information included in this book will be stimulating and will favorably impact research currently performed by the readers of this book.
Author: Brookhaven National Laboratory. National Synchrotron Light Source
Publisher:
ISBN:
Category :
Languages : en
Pages : 244
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Author: Derrick Resha Dean
Publisher:
ISBN:
Category :
Languages : en
Pages : 674
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Book Description
The crystal structure and morphology of a family of aromatic-aliphatic azomethine polyethers (where the aliphatic unit was composed of CH$sb2$ units ranging in length from n = 1, 4, 7, 8, 9 and 10) has been examined primarily by Electron microscopy(EM) and Electron diffraction(ED). Chain folded single crystals with lamellar thicknesses of 35-100A, in which the molecular axis is perpendicular to the substrate, have been grown by slow cooling thin films from the nematic state on a glycerin surface for n = 4, 8 and 10 with AZMEP-7 yielding disclination domains with isolated regions of chain folded lamellae. For as-polymerized AZMEP-10, the lamellae were found to be 35A thick The thinness of the lamellae and their tilt relative to the substrate and molecular axis suggests a regular, adjacent re-entry type folding every three repeat distances. AZMEP-1 was found to crystallize as striated films of near uniform thickness; in these samples, the molecular axes are parallel to the substrate, yielding fiber-type ED patterns. AZMEP-9 samples yielded a similar morphology, but no ED patterns were obtained. Our findings on samples crystallized as thin films has added to earlier findings by S. Kent and P. H. Geil, which gave the first conclusive evidence of chain folding in lcps. Claims were also made by them, and is supported by our findings, of the presence of chain folding in the nematic state. Sheared samples with lamellae ca. 250A and more or less perpendicular to the shear direction have been obtained for n = 1, 4, 7, 8, 9 and 10. Annealing below T$rmsb{k-m}$ has been shown to increase the lamellar thickness and overall order. ED from sheared, annealed samples surprisingly yield h01 single crystal patterns rather than the expected fiber patterns, which have rotational symmetry. This finding is unique, as far as we know, for sheared polymer samples. The h01 single crystal nature of these samples was verified by dark field EM. Lamellar single crystals (ca. 100A thick) have been grown by the constrained film melt polymerization technique for n = 4, 8 and 9, yielding single crystals suitable for ED. The ED data from these samples, in conjunction with data obtained from the sheared samples, has permitted characterization of the unit cells. We have examined creep above and below the nominal Tg in both the viscoelastic and viscoplastic load ranges for AS4/J1 uniaxial composites. Surprisingly, long term creep in tension does not appear to be a problem; it was found to be compensated by shrinkage due to physical aging, resulting in negative creep in the viscoelastic load range, and near zero creep in the viscoplastic load range. This fact makes the time-temperature superposition principle invalid for long term predictions; it actually overpredicts it in tension. The fact that physical aging occurs above Tg in subcrystalline polymers is attributed to the presence of a distributed Tg.
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 886
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Author: Vijay Kumar Thakur
Publisher: Springer
ISBN: 3319202707
Category : Technology & Engineering
Languages : en
Pages : 536
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Book Description
This book introduces various applications of liquid crystalline polymers as the emerging new class of high performance novel materials. The authors detail the advantageous properties of these LCs including optical anisotropic, transparency and easy control over structure. This interdisciplinary work includes valuable input from international projects with special focus on the use of liquid crystalline polymers and/or nanocomposites.
Author: Mark T. DeMeuse
Publisher: Elsevier
ISBN: 0857099019
Category : Technology & Engineering
Languages : en
Pages : 233
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Book Description
Polymer blends offer properties not easily obtained through the use of a single polymer, including the ability to withstand high temperatures. High Temperature Polymer Blends outlines the characteristics, developments, and use of high temperature polymer blends. The first chapter introduces high temperature polymer blends, their general principles, and thermodynamics. Further chapters go on to deal with the characterization of high temperature polymer blends for specific uses, such as fuel cells and aerospace applications. The book discusses different types of high temperature polymer blends, including liquid crystal polymers, polysulfones, and polybenzimidazole polymer blends and their commercial applications. High Temperature Polymer Blends provides a key reference for material scientists, polymer scientists, chemists, and plastic engineers, as well as academics in these fields. Reviews characterization methods and analysis of the thermodynamic properties of high temperature polymer blends Reviews the use of materials such as liquid crystals as reinforcements as well as applications in such areas as energy and aerospace engineering
Author: Melissa Kay Thomas
Publisher:
ISBN:
Category : Liquid crystals
Languages : en
Pages : 70
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Book Description
