پایان نامه بررسی ساختار و خواص نانوکامپوزیت های پلی اتیلن اکسید
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این پایان نامه به زبان انگلیسی، مربوط به دپارتمان
الکترونیک و کامپیوتر دانشگاه ساوت‌همپتون (University of Southampton)
انگلستان میباشد که در سال 2010 انجام و با رتبه عالی مورد تایید قرار
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Abstract
Polymer nanocomposites have attracted great interest over many years, because of the enhanced properties exhibited by such systems. However, it is only recently that the electrical characteristics of this class of material have begun to be studied in detail. Whenever fillers are added to a host polymer matrix, dispersion is of critical importance since, while a well dispersed nanophase may be beneficial, poor dispersion can have negative consequences. Hence, for the nanocomposites to be used appropriately and provide the best properties, a method for observing the dispersion within the matrix is useful. Despite this, evaluating the dispersion of nano-additives in the bulk is far from straight forward using conventional solid-state materials characterization techniques. This study set out to consider the influence of nano-additives on the physical, thermal and electrical properties of poly(ethylene oxide) systems. The initial objective is to investigate the extent to which dispersion of nanofillers and effect of host molecular weight can be inferred from rheological analysis. This investigation covers many systems based upon polyethylene oxide (PEO); PEO blends, thermally aged PEO and PEO composites with montmorillonite (MMT), micro/nano silicon dioxide (SD/nSD) and boehmite fillers (BO). The study continued from dispersion and solution characterisation onto thermal and electrical properties. The effects of additives and treatment on the crystallisation kinetics and thermal transitions are considered. Polymers are most well known for their electrically insulating properties, therefore electrical analysis into AC breakdown and dielectric spectroscopy were also performed. The research has shown that rheology is capable of producing well dispersed PEO nanocomposites. Addition of fillers during the rheology phase produced the expected monotonic increase in viscosity apart from boehmite, which formed a very viscous gel after reaching a threshold loading. Large drops in thermal transitions were observed for the composite samples. All fillers caused a large increase in breakdown strength at higher loadings, except boehmite which caused the breakdown strength to decrease,an effect discussed in detail.
Polymer nanocomposites have attracted great interest over many years, because of the enhanced properties exhibited by such systems. However, it is only recently that the electrical characteristics of this class of material have begun to be studied in detail. Whenever fillers are added to a host polymer matrix, dispersion is of critical importance since, while a well dispersed nanophase may be beneficial, poor dispersion can have negative consequences. Hence, for the nanocomposites to be used appropriately and provide the best properties, a method for observing the dispersion within the matrix is useful. Despite this, evaluating the dispersion of nano-additives in the bulk is far from straight forward using conventional solid-state materials characterization techniques. This study set out to consider the influence of nano-additives on the physical, thermal and electrical properties of poly(ethylene oxide) systems. The initial objective is to investigate the extent to which dispersion of nanofillers and effect of host molecular weight can be inferred from rheological analysis. This investigation covers many systems based upon polyethylene oxide (PEO); PEO blends, thermally aged PEO and PEO composites with montmorillonite (MMT), micro/nano silicon dioxide (SD/nSD) and boehmite fillers (BO). The study continued from dispersion and solution characterisation onto thermal and electrical properties. The effects of additives and treatment on the crystallisation kinetics and thermal transitions are considered. Polymers are most well known for their electrically insulating properties, therefore electrical analysis into AC breakdown and dielectric spectroscopy were also performed. The research has shown that rheology is capable of producing well dispersed PEO nanocomposites. Addition of fillers during the rheology phase produced the expected monotonic increase in viscosity apart from boehmite, which formed a very viscous gel after reaching a threshold loading. Large drops in thermal transitions were observed for the composite samples. All fillers caused a large increase in breakdown strength at higher loadings, except boehmite which caused the breakdown strength to decrease,an effect discussed in detail.
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