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Synthesis And Characterization Of Polymer Layered Silicate Nanocomposites By Emulsion Polymerization Using Organically Modified Synthetic Laponite Clay Platelets
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Book Synopsis Synthesis and Characterization of Polymer/Layered Silicate Nanocomposites by Emulsion Polymerization Using Organically-modified Synthetic Laponite Clay Platelets by : Norma Lidia Negrete Herrera
Download or read book Synthesis and Characterization of Polymer/Layered Silicate Nanocomposites by Emulsion Polymerization Using Organically-modified Synthetic Laponite Clay Platelets written by Norma Lidia Negrete Herrera and published by . This book was released on 2005 with total page 227 pages. Available in PDF, EPUB and Kindle. Book excerpt: L'objectif principal de cette thèse est la synthèse et la caractérisation des nanocomposites poly(styrène-co-acrylate de butyle)/Laponite par polymérisation en émulsion. Dans ce travail nous décrivons l'élaboration de particules nanocomposites par polymérisation en émulsion en présence de Laponite modifiée. Cette modification a été réalisée par deux voies: sois par greffage d'agents de couplage silanes; soit échange cationique. Le procédé de synthèse est divisé en trois étapes: a) la modification organique, b) la redispersion aqueuses de particules d'argile modifiées, et c) la polymérisation en émulsion. Différentes techniques de caractérisation nous ont permis de mener des investigations précises quant aux différentes étapes réactionnelles te de proposer un mécanisme de formation des particules composite aussi obtenues.
Book Synopsis Polymer/layered Silicate Nanocomposites by : Masami Okamoto
Download or read book Polymer/layered Silicate Nanocomposites written by Masami Okamoto and published by iSmithers Rapra Publishing. This book was released on 2003 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: The review sets out to highlight the major developments in this field over the last decade. The different techniques used to prepare PLS nanocomposites are covered. The physicochemical characterisation of PLS nanocomposites and the improved materials properties that those materials can display are discussed. An additional indexed section containing several hundred abstracts from the Rapra Polymer Library database provides useful references for further reading.
Book Synopsis Synthesis and Characterization of Structurally Well-defined Polymer-layered Silicate Nanocomposites by :
Download or read book Synthesis and Characterization of Structurally Well-defined Polymer-layered Silicate Nanocomposites written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract Polymer-layered silicate (PLS) nanocomposites are often based on natural clays such as montmorillonite. In EPR and NMR studies of the surfactant layer that compatibilizes the silicate and the polymer, we found that the iron content in these natural clays is detrimental, as it broadens spectra and shortens relaxation times. The problem was overcome by using as a layered silicate iron-free and structurally well defined magadiite, which was synthesized by a hydrothermal method. The morphology of the magadiite and the extent of intercalation in melt-prepared polymer-organo-magadiite nanocomposites were characterized by scanning electron microscopy ΔΚ� αλγ ςζγδ�αλϛιδ τ�οαυ πϐαϟϟδοζλϛ ��ΑΤΠ� οδπνδϐϟζσδιυ� Ακμλϛ γζεεδοδλϟ ϟυνδπ με νμιυκδοπ� ϟϝμπδ ςζϟϝ ϐαοβμλυι ϛομρνπ αννδαο ϟμ ζλϟδοϐαιαϟδ κμοδ δαπζιυ� �ζϟϝ ζομλ�εοδδ καϛαγζζϟδ� νμιυϐανομιαϐϟμλδ �Ν�Ι� ςαπ εμρλγ ϟμ ζλϟδοϐαιαϟδ ζλϟμ βμϟϝ ακκμλζρκ προεαϐϟαλϟ κμγζεζδγ αλγ νϝμπνϝμλζρκ προεαϐϟαλϟ κμγζεζδγ μοϛαλμκαϛαγζζϟδπ� Βυ ρπζλϛ πζϟδ�πνδϐζεζϐ λζϟομτζγδ πνζλ νομβδπ αλγ αννιυζλϛ �� ΔΝΟ ��μλϟζλρμρπ �ασδ Διδϐϟομλ Ναοακαϛλδϟζϐ Οδπμλαλϐδ� αλγ νριπδ ΔΝΟ ϟδϐϝλζξρδπ ϟϝδ γυλακζϐπ αλγ πναϟζαι πϟορϐϟροδ με προεαϐϟαλϟ ιαυδοπ ζλ πρϐϝ λαλμϐμκνμπζϟδπ� ςδοδ πϟργζδγ� Πϟαϟζϐ “Ϝ Λρϐιδαο Καϛλδϟζϐ Οδπμλαλϐδ �ΛΚΟ� μλ πνδϐζεζϐαιιυ γδρϟδοαϟδγ ϐαϟζμλζϐ προεαϐϟαλϟπ ςαπ αιπμ αννιζδγ ϟμ αϐϐδππ προεαϐϟαλϟ κμϟζμλ μλ α ϐμκνιδκδλϟαου ϟζκδ πϐαιδ �κζιιζπδϐμλγπ ϟμ κζϐομπδϐμλγπ� ϐμκναοδγ ϟμ ΔΝΟ �λαλμπδϐμλγπ�� Βυ �� ΔΝΟ αλγ “Ϝ ΛΚΟ� εαπϟ κμϟζμλ με προεαϐϟαλϟ ιαυδοπ ςαπ εμρλγ ϟμ βδ νομλμρλϐδγ βυ ζλϟδοϐαιαϟζμλ με Ν�Ι ςϝζιδ ζϟ γζκζλζπϝδπ ζλ λμλ�ζλϟδοϐαιαϟδγ κζϐομϐμκνμπζϟδπ ςζϟϝ νμιυπϟυοδλδ �ΝΠ�� Ϟϝδ ομϟαϟζμλαι ϐμοοδιαϟζμλ ϟζκδπ �ϐ αλγ αϐϟζσαϟζμλ δλδοϛζδπ Δα οδσδαι γζεεδοδλϟ οδϛζκδπ με οδμοζδλϟαϟζμλ με προεαϐϟαλϟ κμιδϐριδπ ςζϟϝ ζλϐοδαπζλϛ ϟδκνδοαϟροδ� Ϟϝδ ϟοαλπζϟζμλ ϟδκνδοαϟροδ βδϟςδδλ ϟϝδ οδϛζκδπ ζπ οδιαϟδγ ϟμ Ϟϛ με ΝΠ ζλ κζϐομϐμκνμπζϟδπ αλγ ϟμ ϟϝδ κδιϟζλϛ ϟδκνδοαϟροδ Ϟκ με Ν�Ι ζλ λαλμϐμκνμπζϟδπ� Ϟϝδ ζομλ�εοδδ καϛαγζζϟδ ιδαγπ ϟμ πρβπϟαλϟζαιιυ ιμλϛδο διδϐϟομλ�
Book Synopsis Polymer-Layered Silicate and Silica Nanocomposites by : Y.C. Ke
Download or read book Polymer-Layered Silicate and Silica Nanocomposites written by Y.C. Ke and published by Elsevier. This book was released on 2005-07-13 with total page 405 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer-Layered Silicate and Silica Nanocomposites includes advanced materials and nanocomposites based on silica and layered silicates obtained from resources in China. Using nanotechnology, these inorganic materials can be filled, in-situ polymerised and combined with polymers with nanoscale dispersions. In this book, many practical examples are presented to show how to prepare the nanocomposites. Several kinds of polymer (PET,PBT,PE,PP,etc.)-layered silicate and silica nanocomposites are prepared and investigated based on our research works, inventions and applications. They are prepared and modified aiming at their applications to such fields as, functional films, barrier materials, coatings, and engineering plastics. Their structure-property relationship, especially the nano effects from them are investigated under different techniques to show how the critical load of the inorganic phase has the effect on the final properties of the nanocomposite materials. Obviously, this new generation of materials has revolutionary effects on the traditional materials or industry as petroleum. Some of the prospects of them are thus included. Focus on the inorganic phase, which is of wide practical and industrial significance Dealing with many first report of the nanoeffect, nanostructure and its functional properties Especially, it covers the particle assembly and self-assemble by interaction with polymer matrix
Book Synopsis In-situ Synthesis of Polymer Nanocomposites by : Vikas Mittal
Download or read book In-situ Synthesis of Polymer Nanocomposites written by Vikas Mittal and published by John Wiley & Sons. This book was released on 2011-10-05 with total page 593 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book series "Polymer Nano-, Micro- and Macrocomposites" provides complete and comprehensive information on all important aspects of polymer composite research and development, including, but not limited to synthesis, filler modification, modeling, characterization as well as application and commercialization issues. Each book focuses on a particular topic and gives a balanced in-depth overview of the respective subfi eld of polymer composite science and its relation to industrial applications. With the books the readers obtain dedicated resources with information relevant to their research, thereby helping to save time and money. In-situ intercalative polymerization in the presence of filler provides distinct advantages when compared to other nanocomposite synthesis techniques including the possibility to polymerize a large range of thermoplastic and thermosetting polymers, improved handling of gaseous or liquid monomers or high pressure polymerization and improved control of heat of polymerization. This volume aims to highlight these advantages of the generation of polymer nanocomposites with a large spectrum of polymer matrices. Following an overview of the synthesis methodologies, the text goes on to discuss the most relevant polymer materials, including polyamides, polyolefi nes, polyacrylates, polyethylenes, polyurethanes, polyesters and polyepoxides.
Book Synopsis Synthesis, Characterization, and Processibility of Polystyrene (PS)/clay Nanocomposite Prepared by Emulsion Polymerization Followed by Heterocoagulation by : Sang Hoon Lee
Download or read book Synthesis, Characterization, and Processibility of Polystyrene (PS)/clay Nanocomposite Prepared by Emulsion Polymerization Followed by Heterocoagulation written by Sang Hoon Lee and published by . This book was released on 2005 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The objective of this research was to synthesize polystyrene (PS)/clay nanocomposites by emulsion polymerization followed by heterocoagulation, characterize the resulting nanocomposites, investigate their rheological behavior, and establish a reliable structure-property-processibility relationship. A series of cationic polymer latex particles was synthesized by emulsion polymerization with or without surfactants and used for the preparation of polymer layered silicate (PLS) nanocomposites. Both the emulsifier-free emulsion polymerization with the reactive comonomer, ((4-vinylbenzyl) trimethyl ammonium chloride (VTAC)), and that with the cationic initiator, 2,2'-azobis(2-methylpropionamide) dihydrochloride (V-50), form polymers with ammonium groups in the chain. Several types of ammonium- or imidazolium-containing compounds such as cetyltrimethyl-ammonium bromide (CTAB) and 3-hexadecyl-1-methyl imidazolium bromide (HMIB), and pristine silicates such as Gelwhite® GP, Cloisite® Na, Lapointe® XLS, and SOMASIF® ME-100 were employed to prepare PLS nanocomposites. We studied the morphology, coagulation process, oxidative thermal stability, mechanical properties, and melt rheology of the resulting composites, using wide angle X-ray diffraction (WAXD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA), tensile measurements and dynamic frequency sweep experiments. TEM analysis displayed that the heterocoagulation process strongly depended on the type and concentration of silicates, and the particle size of the latex. The combination of WAXD and TEM proved that the morphology of the PS nanocomposites could be controlled by the type and amount of surfactant/initiator and clay content. The thermal stability of the nanocomposites was improved up to 100°C with 5 wt% of silicate incorporated and depended on the interaction between polymer and silicate as well as the presence of free surfactants. However, differential scanning calorimetry and dynamic mechanical thermal analysis measurements indicated that the PS/clay nanocomposites showed no significant changes in Tg. The introduction of nonreactive surfactant produced a more stable latex and lowered the degree of crosslinking between polymer chains and the clay, lowering the melt viscosity. Lowering the degree of crosslinking enhanced the processing. Injection molded dumbbell-shape samples were not significantly discolored and were employed as specimens for the tensile testing. Young's modulus of the sample containing 5 wt% silicates was enhanced up to 40%, without sacrificing other properties including toughness. From the investigation of the linear dynamic viscoelastic properties of the PS nanocomposite, we found that the dynamic storage modulus not only increased and showed solid-like behavior as the clay content increased, but also increased as the temperature was increased from 180 to 220°C when a high content of silicate was incorporated. In addition, the viscoelastic behavior strongly depends on the type of the silicate and molecular weight of PS."--P. iii-iv.
Book Synopsis Journal of Nanoscience and Nanotechnology by :
Download or read book Journal of Nanoscience and Nanotechnology written by and published by . This book was released on 2006 with total page 976 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Polymer Nanoclay Composites by : Stephan Laske
Download or read book Polymer Nanoclay Composites written by Stephan Laske and published by William Andrew. This book was released on 2015-01-09 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is a major lack of fundamental knowledge and understanding on the interaction between a filler and the polymer matrix. When it comes to nanoscale fillers, such as layered silicates, carbon nanotubes, graphene or cellulose nanofibers it is even more important to know accurate structure-property relationships as well as identifying the parameters influencing material behavior. The reason for the lack of knowledge on how to process nanocomposites and why there are so few applications is that several scientific fields are affected and a joint effort of those scientific communities involved is necessary – starting from the filler manufacturing or pre-processing over polymer chemistry to the polymer processing. In Polymer Nanoclay Composites, all involved scientific areas are viewed together for the first time, providing an all-embracing coverage of all stages of polymer clay nanocomposites processing from lab-scale to industrial scale – stages from the raw material over manufacturing of polymer clay nanocomposites to characterization and the final products. Readers will gain insight in the physical/chemical pre-processing of layered silicates and their incorporation into a polymer matrix using sophisticated technologies (such as advanced compounding) as well as in real-time quality control of the nanocomposite production and future prospects. The book also describes nanotoxicological and nanosafety aspects. Covers the whole processing route with all aspects of the nanocomposites industry with particular focus on the processing of polymer clay nanocomposites Includes quality control and nanosafety Multidisciplinary approach from an industrial perspective
Book Synopsis Clay-Polymer Nanocomposites by : Khouloud Jlassi
Download or read book Clay-Polymer Nanocomposites written by Khouloud Jlassi and published by Elsevier. This book was released on 2017-07-26 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt: Clay–Polymer Nanocomposites is a complete summary of the existing knowledge on this topic, from the basic concepts of synthesis and design to their applications in timely topics such as high-performance composites, environment, and energy issues. This book covers many aspects of synthesis such as in- situ polymerization within the interlamellar spacing of the clays or by reaction of pristine or pre-modified clays with reactive polymers and prepolymers. Indeed, nanocomposites can be prepared at industrial scale by melt mixing. Regardless the synthesis method, much is said in this book about the importance of theclay pre-modification step, which is demonstrated to be effective, on many occasions, in obtaining exfoliated nanocomposites. Clay–Polymer Nanocomposites reports the background to numerous characterization methods including solid state NMR, neutron scattering, diffraction and vibrational techniques as well as surface analytical methods, namely XPS, inverse gas chromatography and nitrogen adsorption to probe surface composition, wetting and textural/structural properties. Although not described in dedicated chapters, numerous X-ray diffraction patterns of clay–polymer nanocomposites and reference materials are displayed to account for the effects of intercalation and exfoliations of layered aluminosilicates. Finally, multiscale molecular simulation protocols are presenting for predicting morphologies and properties of nanostructured polymer systems with industrial relevance. As far as applications are concerned, Clay–Polymer Nanocomposites examines structural composites such as clay–epoxy and clay–biopolymers, the use of clay–polymer nanocomposites as reactive nanocomposite fillers, catalytic clay-(conductive) polymers and similar nanocomposites for the uptake of hazardous compounds or for controlled drug release, antibacterial applications, energy storage, and more. The most comprehensive coverage of the state of the art in clay–polymer nanocomposites, from synthesis and design to opportunities and applications Covers the various methods of characterization of clay–polymer nanocomposites - including spectroscopy, thermal analyses, and X-ray diffraction Includes a discussion of a range of application areas, including biomedicine, energy storage, biofouling resistance, and more
Book Synopsis Self-Healing Polymers by : Wolfgang H. Binder
Download or read book Self-Healing Polymers written by Wolfgang H. Binder and published by John Wiley & Sons. This book was released on 2013-03-29 with total page 638 pages. Available in PDF, EPUB and Kindle. Book excerpt: Self-healing is a well-known phenomenon in nature: a broken bone merges after some time and if skin is damaged, the wound will stop bleeding and heals again. This concept can be mimicked in order to create polymeric materials with the ability to regenerate after they have suffered degradation or wear. Already realized applications are used in aerospace engineering, and current research in this fascinating field shows how different self-healing mechanisms proven successful by nature can be adapted to produce even more versatile materials. The book combines the knowledge of an international panel of experts in the field and provides the reader with chemical and physical concepts for self-healing polymers, including aspects of biomimetic processes of healing in nature. It shows how to design self-healing polymers and explains the dynamics in these systems. Different self-healing concepts such as encapsulated systems and supramolecular systems are detailed. Chapters on analysis and friction detection in self-healing polymers and on applications round off the book.
Book Synopsis Synthesis of Nanocomposites with Anisotropic Properties by Controlled Radical Emulsion Polymerization Lorena by : Thaissa De Camargo Chaparro
Download or read book Synthesis of Nanocomposites with Anisotropic Properties by Controlled Radical Emulsion Polymerization Lorena written by Thaissa De Camargo Chaparro and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of this work is to prepare Laponite RD-based nanocomposite latexes by aqueous emulsion polymerization, using the reversible addition-fragmentation chain transfer (RAFT) polymerization. Laponite platelets were selected as the inorganic filler due, especially, to their anisotropic shape, which allows the production of nanostructured films, but also for their thermal and mechanical properties, their high chemical purity and the uniform dispersity of the platelets. Hydrophilic polymers (macroRAFT) composed of poly(ethylene glycol) (PEG), acrylic acid (AA) or N,N-dimethylaminoethyl methacrylate (DMAEMA) and comprising hydrophobic n-butyl acrylate (BA) units (in some cases) and trithiocarbonate terminal group were initially synthesized. Then, the interaction between the macroRAFTs and the clay was studied through the plot of adsorption isotherms. By acting as coupling agents and stabilizers, the macroRAFT agents were used in the emulsion copolymerization of methyl (meth)acrylate and BA by semi-continuous process in the presence of the clay. Hybrid latex particles with different morphologies were obtained and the results were associated to the nature and concentration of the RAFT (co)polymers, to the pH of the macroRAFT/Laponite dispersion, the glass transition temperature of the final copolymer (function of the composition of the hydrophobic monomers mixture) and to the polymerization conditions. The cryo-TEM images indicate the formation of polymerdecorated Laponite platelets (several latex particles located at the surface of the platelets), dumbbell-like, janus, Laponite-decorated (armored) latex particles, and multiple encapsulated particles (several platelets inside each latex particle). The mechanical properties of polymer/Laponite films were studied by dynamic mechanical analysis and correlated with the particles morphology and the films microstructure.
Book Synopsis Polymer Clay Nano-composites by : Stefano Leporatti
Download or read book Polymer Clay Nano-composites written by Stefano Leporatti and published by MDPI. This book was released on 2019-10-30 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Special Issue focuses on the current state-of-the-art of “Polymer Clay Nano-Composites” for biomedical, anticorrosion, antibacterial, and other applications. Clay–polymer composite nanomaterials represent an emerging area of research. Loading polymers with clay particles essentially enhances the composite strength features. Of particular interest are different nano-assembly methods, such as silane mono and multilayers, polyelectrolyte layer-by-layer assembly, and others. An important development was reached for tubular and fibrous clay nanoparticles, such as halloysite, sepiolite, and imogolite. Polymer clay nanoparticles can be prepared as sheets with 1-nm thickness and width of a few hundred nm (e.g., kaolin and montmorillonite). Fibrous clays significantly reinforce the nano-composites in the assembly with biopolymers and other green polymers, leading to functional hybrid bio nano-composites. The scope of this Special Issue comprehensively includes the synthesis and characterization of polymer clay nano-composites used for several applications, including nano-clay polymer composites and hybrid nano-assemblies.
Book Synopsis Synthesis and Characterization of Polymer-layered Silicate Nanocomposites by : Xiao-an Fu
Download or read book Synthesis and Characterization of Polymer-layered Silicate Nanocomposites written by Xiao-an Fu and published by . This book was released on 2001 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Polymer Nanocomposites by : Vikas Mittal
Download or read book Polymer Nanocomposites written by Vikas Mittal and published by Nova Science Publishers. This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer nanocomposites revolutionised the research in this field owing to the tremendous improvement in the composite properties at very low filler volume fraction. The surface modification of the filler, generally layered silicate montmorillonite clay, is required to compatibilise the organic and inorganic phases. The inorganic clay was modified conventionally with alkyl ammonium ions and the exfoliated nanocomposites with polar polymers could be formed where the clay could be dispersed at nanometer scale. During the initial phase of nanocomposite developments, only ammonium ions of fixed chain length were exchanged on the clay surface. However, this technology suffered when polyolefins and other non-polar polymers were used owing to the difficulties in dispersion of polar clay in the hydrophobic matrices. At best, only partially exfoliated composites could be formed by using these ammonium modified clays. To circumvent these limitations, two possible routes have been followed. By polarising the polymer matrix (e.g. by addition of compatibilisers or surfactants), one can achieve compatibilisation between the organic-inorganic phases. However, this technology leads to deterioration of nanocomposite properties even though better delamination is achieved. On the other hand, one can also focus on the more efficient modification of the filler surface so that the residual polarity after modification of the surface with conventional ammonium ions is also eliminated. A number of new clay surface modification techniques have been developed in the recent years which help in the generation of more exfoliated polymer nanocomposites. These techniques do not rely on the ion exchange of fixed chain length ammonium ions, but lead to generation/exchange of long and polydisperse polymer chains. These techniques include grafting of polymers to the clay surface, grafting of polymers from the clay surface, controlled living polymerisation from the clay surface, in situ generation of polyolefins from the clay surface and clay surface reactions etc. and form very robust technologies for the complete organophilisation of the clay surface. The generation of thick brushes around the clay surface owing to the better surface modification leads to better coverage of the electrostatic forces binding the clay platelets together and also leads to higher basal plane spacing between them. As a result, the modified platelets are more susceptible to exfoliation when compounded with the polymer matrices.
Book Synopsis Clay-based Polymer Nanocomposites (CPN) by : Kathleen A. Carrado
Download or read book Clay-based Polymer Nanocomposites (CPN) written by Kathleen A. Carrado and published by . This book was released on 2007 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Generation and Thermo-mechanical Characterization of Advanced Polyamide-6,6 Nanocomposites Using Interfacial Polycondensation by : Zehra Sibel Kalkan
Download or read book The Generation and Thermo-mechanical Characterization of Advanced Polyamide-6,6 Nanocomposites Using Interfacial Polycondensation written by Zehra Sibel Kalkan and published by . This book was released on 2006 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Nanocomposites comprising either pristine or organically modified layered silicates or silica were synthesized in-situ via the interfacial polycondensation of polyamide-6,6; the silica was also generated in-situ via sol-gel reactions during the nylon polymerization. The thermo-mechanical properties of these nanocomposites were evaluated by Thermogravimetric Analysis (TGA) and Dynamic Mechanical Analysis (DMA). In addition, Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Wide Angle X-Ray Diffraction (WAXD), and Energy Dispersive Spectroscopy (EDS) measurements were used to identify the functional groups, to understand the effect of the filler on the phase transition behavior, to evaluate the basal spacing of clay layers in the case of layered silicate nanocomposites, and to observe the presence and dispersion of chemical elements, respectively. The evaluation of reaction variables via statistically designed experiments revealed that the concentration ratio of hexamethylenediamine to adipoyl chloride and the type of mixing imparted to the reaction mixture are important variables affecting molecular weight. It was found that the final clay content in the nanocomposites can be adjusted by changing the concentration of the clay selectively dispersed in one of the reagent phases. The synthesis of dispersed layered silicate nanocomposites required producing a colloidal dispersion of the clay prior to mixing it with the reactive monomers. Stirring was found to be critical in terms of keeping clay dispersed during the polymerization. Better dispersion of the layered silicates in the nanocomposites was achieved with longer mixing times in stirred reactors. The presence of surfactants in the clay galleries resulted in the formation of imperfect (lower-melting) nylon crystals from the melt. Enhancement in thermal stability and mechanical stiffness was observed with the addition of layered silicates to the polymerized nylon. Silica particles could be co-generated in-situ using sol-gel chemistry at reaction times or residence times varying from 15 sec to 2 min. Variation in the molar ratio of water to tetraethoxysilane (TEOS), designated by r, results in different silica morphology, ranging from predominantly spherical particles at r ratios of 10 to 20 to agglomerates or open network structures at r ratios from 100 to 890. It was found that generation of silica in the reaction systems using smaller quantities of water gave rise to low molecular weight polyamide chains and also altered their crystallization and melting behavior. Imperfect nylon crystals in these nanocomposites gave rise to three melting peaks associated with different crystal structures. Such effects of filler on phase transition behavior diminished when the polymer molecular weight increased at higher r ratios. Hybrids incorporating chemical connectivity between the inorganic parts (generated from sol-gel reactions) and the polyamide chains generated using a coupling agent exhibited differences in crystalline structure depending upon the extent of reaction. Hybrids were found to have superior mechanical stiffness as compared to unfunctionalized silica nanocomposites, which is attributed to the chemical bonding between the polymer chains and the inorganic structure of the hybrids. Variations in the nylon molecular weight observed with addition of either coupling agent or layered silicate co-reinforcement are attributed to changes in the mass transfer of the polycondensation reagents to the reaction zone. The especially dramatic changes in molecular weight with the addition of the (3-Aminopropyl) triethoxysilane (APTES) coupling agent are attributed to its lower solubility in water vs. TEOS. The dispersion of sodium montmorillonite (NaMMT) layered silicate in the nanocomposites could be improved by the in-situ co-generation of silica in unstirred reactors. Nanocomposite mass is rendered more stable (less fugitive) at elevated temperature in the presence of such hybrid structures as compared to neat PA66."--abstract.
Book Synopsis Recent Advances in Polymer Nanocomposites: Synthesis and Characterisation by : Sabu Thomas
Download or read book Recent Advances in Polymer Nanocomposites: Synthesis and Characterisation written by Sabu Thomas and published by CRC Press. This book was released on 2010-08-03 with total page 446 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book examines the current state of the art, new challenges, opportunities, and applications in the area of polymer nanocomposites. Special attention has been paid to the processing-morphology-structure-property relationship of the system. Various unresolved issues and new challenges in the field of polymer nanocompostes are discussed. The influence of preparation techniques (processing) on the generation of morphologies and the dependence of these morphologies on the properties of the system are treated in detail. This book also illustrates different techniques used for the characterization of polymer nanocomposites. The handpicked selection of topics and expert contributors across the globe make this survey an outstanding resource reference for anyone involved in the field of polymer nanocompostes for advanced technologies.
