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| Autor | Sati N. Bhattacharya, Musa R. Kamal, Rahul K. Gupta |
| Titel | Polymeric Nanocomposites. Theory and Practice |
| Ort | München |
| Verlag | Hanser |
| Jahr | 2008 |
Literaturverz. |
yes |
| Fußnoten | yes |
| Fragmente | 15 |
| [1.] Mrs/Dublette/Fragment 064 03 - Diskussion Zuletzt bearbeitet: 2015-05-17 09:03:05 WiseWoman | Bhattacharya et al. 2008, Dublette, Fragment, Gesichtet, KeineWertung, Mrs, SMWFragment, Schutzlevel sysop |
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| 5.5. Thermal characterization [242-244]
Thermal characterizations are generally defined as techniques in which a property of a specimen is continuously measured through a pre-determined temperature. |
6.7 Thermal Characterization
Thermal characterizations are generally defined as techniques in which a property of a specimen is continuously measured through a pre-determined temperature profile. |
Fortsetzung in Mrs/Fragment 064 07 |
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| Nanotechnology has created a key revolution in the 21th century exploiting the new properties, phenomena and functionalities exhibited by matters when dealt at the level of few nanometers as opposed to hundred nanometers and above [8]. Nanoscale materials are already recognized as unique because they produce qualitatively new behavior when compared with their macroscopic counterpart. It is understood that when the domain size within the materials becomes comparable with the physical length scale, such as segments of a polymer macromolecule, the expected physical phenomena and the response to any external disturbance do not follow the established principles.
[8] S. N.Bhattacharya, Rahul K. Gupta, Polymeric Nanocomposites Theory and Practice, Hanser 2008 |
Nanotechnology has created a key revolution in the 21st century exploiting the new properties, phenomena and functionalities exhibited by matters when dealt at the level of few nanometers as opposed to hundred nanometers and above. Nanoscale materials are already recognized as unique because they produce qualitatively new behavior when compared with their macroscopic counterparts. It is understood that when the domain size within the materials becomes comparable with the physical length scale, such as segments of a polymer macromolecule, the expected physical phenomena and the response to any external disturbance do not follow the established principles. |
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| 1.3. Polymer Nanocomposite
Nanocomposite technology is a new developing field, in which nanofiller are added to a polymer to reinforce and provide novel characteristics. Nanocomposite technology is applicable to a wide range of polymers from thermoplastics and thermosets to elastomers. Two decades ago, researchers from Toyota Central Research and Development produced a new group of polymer-clay complexes or composites, which was aptly called polymer-layered silicate nanocomposite. Today, there is a variety of nanofillers used in nanocomposites. The most common types of fillers are natural clays, synthetic clays, nanostructured silicas, nanoceramics and carbon nanotubes. The property enhancements have allowed these materials to commercially compete with traditional materials [8]. [8] S. N.Bhattacharya, Rahul K. Gupta, Polymeric Nanocomposites Theory and Practice, Hanser 2008 |
1.1 Polymer Nanocomposites
Nanocomposite technology is a newly developed field, in which nanofillers are added to a polymer to reinforce and provide novel characteristics. Nanocomposite technology is applicable to a wide range of polymers from thermoplastics and thermosets to elastomers. Two decades ago, researchers from Toyota Central Research and Development produced a new group of polymer-clay complexes or composites, which was aptly called polymer-layered silicate nanocomposites or polymer nanocomposites. Today, there is a variety of nanofillers used in nanocomposites. Cost and availability continue to change as the field is relatively new and several of these fillers are still being developed. The most common types of fillers are natural clays (mined, refined and treated), synthetic clays, nanostructured silicas, nanoceramics, nanocalcium carbonates and nanotubes (carbon based). The properties conferred by the nanoparticles to the polymer matrix are remarkable. The property enhancements have allowed these materials to commercially compete with traditional materials. |
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| The large variety of polymer systems used in nanocomposite preparation can be classified as follow:
1. Thermoplastics 2.2.1. Thermoplastic Thermoplastics, such as polypropylene (PP), polyethylene (PE), copolymers such as poly (ethylene-co vinyl acetate) (EVA), poly (ethylene propylene diene) rubber (EPDM), polyamides (PA), poly – ethylene terephthalate (PET) and polystyrene (PS) have been used as polymer matrices for the preparation of nanocomposites. |
The large variety of polymer systems used in nanocomposite preparation can be conventionally classified as follows:
1. Thermoplastics [page 23] 2.3.1 Thermoplastics Thermoplastics, such as polypropylene (PP), polyethylene (PE), copolymers, such as poly (ethylene-co vinyl acetate) (EVA), polyethylene propylene diene) rubber (EPDM), polyamides (PA), poly-thylene terephtalate (PET), polystyrene (PST) and poly (1-butene) have been used as polymer matrices for the preparation of nanocomposites. |
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| Polyurethane (PU) is becoming increasingly important as an engineering material because it has excellent abrasion resistance and displays properties of both elastomers and plastics. Wang and Pinnavaia [29] have synthesized intercalated nanocomposites based on elastomeric polyurethane. Khudyakov and Zopf [49] also studied the effect of colloidal silica and organoclays on properties of PU. The studies on epoxy systems considered the ring opening polymerization of epoxides to form polyether nanocomposites. Studies [30, 31] of both rubbery and glassy epoxy/clay nanocomposites using different type of amine curing agents were [conducted and the mechanisms leading to the mono-layer exfoliation of clay layers in thermoset epoxy systems were elucidated.]
[30] P.B., Messersmith, E.P. Giannelies, Chemical Matterial 6, (1994), 1719-1725 [31] T. Lan, T.J. Pinnavaia, Chemical Materials, 6, 1994, 2216- 2219 |
[page 28]
Polyurethane (PU) is becoming increasingly important as an engineering material because it has excellent abrasion resistance and displays properties of both elastomers and plastics. [page 29] [Wang and Pinnavaia (1998)] have synthesized intercalated nanocomposites based on elastomeric polyurethanes. [page 28] The studies on epoxy systems considered the ring opening polymerization of epoxides to form polyether nanocomposites. Studies of both rubbery and glassy epoxy/clay nanocomposites using different types of amine curing agents were conducted and the mechanisms leading to the monolayer exfoliation of clay layers in thermoset epoxy systems were elucidated. |
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| [Studies [30, 31] of both rubbery and glassy epoxy/clay nanocomposites using different type of amine curing agents were] conducted and the mechanisms leading to the mono-layer exfoliation of clay layers in thermoset epoxy systems were elucidated.
2.2.3. Elastomers Burnside and Giannelis [32] have described the two-step preparation of silicon rubber-based nanocomposites. First, silanol-terminated poly (dimethyl siloxane) (PDMS) was blended at room temperature with dimethyl-ditallow ammonium-exchanged montmorillonite, followed by crosslinking of the silanol end groups with tetra ethyl- orthosilicate (TEOS) in the presence of bis(2-ethylhexanoate) as catalyst at room temperature. Also Okada and co-worker [33] obtained a nitrile rubber (NBR) – based nanocomposite in a dual-step synthesis. 2.2.4. Natural and biodegradable polymers Natural and biodegradable polymers are a new generation of polymers that are relatively friendly to the environment with little or no impact when disposed. Such polymers include polylactide (PLA), starch, and cellulose among others. Although these polymers are considered to be environmentally-friendly, they have relatively weak mechanical properties, such as brittleness, low heat distortion, low tensile strength. And their use in packaging is limited due to high gas permeability [34]. Addition of nano-scale fillers has been shown to improve these properties significantly, allowing these polymers to be used in applications such as disposable food service items, food packaging, health care product, packing foams and agricultural mulch film. PLA polymers are linear aliphatic polyester, generally produced by ring-opening polymerization of lactide dimer. Sinha Ray and Okamoto [35] have shown that the addition of nanoscale modified montmorillonite increased both solid and melt state properties, such as flexural properties, rheological properties, reduced gas permeability and increased rate of biodegradability. Ogata et al. [36] also reported similar enhancement of properties. Another biodegradable polymer is polycaprolactone (PCL), linear polyester manufactured by ring-opening polymerization of ε-caprolactone. The PCL chain is flexible and exhibits high elongation at break and low modulus. Its physical properties make it very attractive, not only as a substitute material for nondegradable polymer but also as a plastic material for medical and agricultural applications. The main drawback of PCL is its low melting point (65°C ), which can be overcome by blending it with other polymers. Many attempts to prepare PCL nanocomposites with much improved mechanical and materials properties than that of neat PCL have been reported [34]. [30] P.B., Messersmith, E.P. Giannelies, Chemical Matterial 6, (1994), 1719-1725 [31] T. Lan, T.J. Pinnavaia, Chemical Materials, 6, 1994, 2216- 2219 [32] S.D., Burnside, E.P. Giannelis, Chemical Materials, 7, (1995), 1597-1600 [33] A. Okada, K. Fujumori, A. Usuki, Polymer Chemistry, 32,(2), 540-541, 1991 [34] S. Sinha Ray, M. Bousmina, Progress in Material Science, 50, 962-1079, 2005 [35] S. Sinha Ray, M. Okamoto, Macromolecule Rapid Communication,24 (14), 815- 840, 2003 [36] N. Ogata, G. jimentz, Journal of polymer science Part B, 35 (2), 389- 396, 1997 |
[S. 28]
Studies of both rubbery and glassy epoxy/clay nanocomposites using different types of amine curing agents were conducted and the mechanisms leading to the monolayer exfoliation of clay layers in thermoset epoxy systems were elucidated. [S.27] 2.3.2 Elastomers [Burnside and Giannelis (1995)] have described the two-step preparation of silicon rubber- based nanocomposites. First, silanol-terminated poly(dimethyl siloxane) (PDMS, Mw= 18000) was melt blended at room temperature with dimethyl-ditallow ammonium- exchanged montmorillonite, followed by cross-linking of the silanol end groups with tetraethyl-orthosilicate (TEOS) in the presence of bis(2-ethylhexanoate) as catalyst at room temperature. [...] [Okada and co-workers (1990), (1991)] obtained a nitrile rubber (NBR)-based nanocomposite in a dual-step synthesis. [S. 29]
Natural and biodegradable polymers are a new generation of polymers that are relatively friendly to the environment with little or no impact when disposed. Such polymers include polylactide (PLA), starch, and cellulose among others. Although these polymers are considered to be environmentally-friendly, they have relatively weak mechanical properties, such as brittleness, low heat distortion, low tensile strength, and their use in packaging is limited due to high gas permeability [Sinha Ray and Bousmina (2005)]. Addition of nanoscale fillers has been shown to improve these properties significantly, allowing these polymers to be used in applications such as disposable food service items, food packaging, health care products, packing foams and agricultural mulch film. PLA polymers are linear aliphatic polyesters, generally produced by ring-opening polymerization of lactide monomers. According to [Sinha Ray and Okamoto (2003)], their mechanical properties, thermal plasticity and biocompatibility are generally good and have much promise in many applications. They have, however, shown that the addition of nanoscale modified montmorillonite increased both solid and melt state properties, such as flexural properties, rheological properties, reduced gas permeability and increased rate of biodegradability. [...] Polycaprolactone (PCL) is a linear polyester manufactured by ring-opening polymerization of ε-caprolactone. [...] The PCL chain is flexible and exhibits high elongation at break and low modulus. Its physical properties and commercial availability make it very attractive, not only as a substitute material for nondegradable polymers for commodity applications, but also as a plastic material for medical and agricultural applications. The main drawback of PCL is its low melting point (65°C), which can be overcome by blending it with other polymers or by radiation cross-linking processes resulting in enhanced properties for a wide range of applications. Many attempts to prepare PCL nanocomposites with much improved mechanical and materials properties than that of neat PCL have been reported [Ray and Bousmina (2005)]. |
The source is not mentioned. All references to the literature except one have been taken from the source. |
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| The two major types of polyamides are polyamide 6 and polyamide 66. PA 6 is prepared by the polymerization of caprolactam. PA 66 is derived from the polycondensation of hexamethyelene diamine with adipic acid. Polyamides are crystalline polymers. The key features include a high degree of solvent resistance, thoughness, and fatigue resistance. Polyamides do exhibit a tendency to creep under applied load. Glass fibers and mineral fillers are often used to enhance the properties of polyamides. In addition, the properties of polyamides are greatly affected by moisture. The largest area of application for polyamide is in fiber and engineering plastic. Molded applications include automotive component, related machine parts (gear, cams, pulleys, rollers, etc.), and electrical insulation.
Earlier studies [79] have illustrated that the addition of clay to PA has improved the strength, stiffness, barrier, and heat resistance properties of polyamide 6. The barrier resins exhibit reduced moisture absorption and increased melt stability. Toyota researchers (1989) have shown that, similar to other nanocomposites, PA nanocomposites are able to achieve a lot of improved characteristics compared to pure PA. Thus, it has been reported that PA6 nanocomposites show higher tensile strength, higher tensile modulus, higher heat distortion temperature, increased solvent resistance, decreased thermal expansion coefficient, reduced gas permeability and increased flame retardancy. With these enhanced properties, PA nanocomposites have found increased application in the automobile and textile industries, where stronger yarn could be produced, with better extensional characteristics [88-90]. |
The two major types of polyamides are nylon 6 and nylon 66. Nylon 6, or polycaprolactam, is prepared by the polymerization of caprolactam. Poly (hexamethylene adipamide), or nylon 66, is derived from the condensation polymerization of hexamethylene diamine with adipic acid. Polyamides are crystalline polymers. Their key features include a high degree of solvent resistance, toughness, and fatigue resistance. Nylons do exhibit a tendency to creep under applied load. Glass fibers or mineral fillers are often used to enhance the properties of polyamides. In addition, the properties of nylon are gready affected by moisture. The largest area of application for nylons is in fibers. Molded applications include automotive components, related machine parts (gears, cams, pulleys, rollers, boat propellers, etc.), appliance parts, and electrical insulation.
Earlier studies have illustrated that the addition of clay to PA has improved the strength, stiffness, barrier, and heat resistance properties of nylon 6. The barrier resins exhibit reduced moisture absorption and increased melt stability. Toyota researchers (1989) have shown that, similar to other nanocomposites, PA nanocomposites are able to achieve much improved characteristics compared to neat PA. It has been reported that PA6 nanocomposites show approximately 40 % higher tensile strength, 68 % higher tensile modulus, 60 % higher flexural strength, 126 % higher flexural modulus, higher heat distortion temperatures, increased solvent resistance, decreased thermal expansion coefficient, reduced gas permeability, and increased flame retardancy. With these enhanced properties, PA nanocomposites have found increased application in the automobile and textile industries, where stronger yarns could be produced, with better extensional characteristics. |
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| 2.5.1. Melt intercalation
Melt intercalation is the most widely used method in polymer/ particle nanocomposite preparation, and it has tremendous potential for industrial application. An advantage of this method over the others is that no solvent is required. The melt intercalation process involves mixing the particles by annealing, statically or under shear, with polymer pellets while heating the mixture above the melting point of the polymer [8]. [8] S. N.Bhattacharya, Rahul K. Gupta, Polymeric Nanocomposites Theory and Practice, Hanser 2008 |
2.2.3 Melt Intercalation
Melt intercalation is the most widely used method in polymer/clay nanocomposite preparation, and it has tremendous potential for industrial application. An advantage of this method over the others is that no solvent is required. The melt blending process involves mixing the layered silicate by annealing, statically or under shear, with polymer pellets while heating the mixture above the softening point of the polymer. |
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| 2.5.3. in-situ polymerization
In -situ polymerization involves the dispersion and distribution of particle in the monomer followed by polymerization. The particle is swollen within the liquid monomer or a monomer solution so that polymer nanocomposite formation can occur during polymerization process. Polymerization can be initiated either by heat or radiation, diffusion of a suitable initiator, or by an organic initiator [8]. [8] S. N.Bhattacharya, Rahul K. Gupta, Polymeric Nanocomposites Theory and Practice, Hanser 2008 |
2.2.2 In-Situ Polymerization
In-situ polymerization involves the dispersion and distribution of clay layers in the monomer followed by polymerization. The layered silicate is swollen within the liquid monomer or a monomer solution so that polymer formation can occur between the intercalated sheets. Polymerization can be initiated either by heat or radiation, diffusion of a suitable initiator, or by an organic initiator or catalyst fixed through cation exchange inside the interlayer before the swelling step. |
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| Electron microscopy is a process of obtaining images using electrons and is frequently used when the magnification required is much larger than what can be achieved by light microscopes that means; when the particles to be monitored are smaller than the wavelength of the visual light (< 400 nm). The physical effect behind this principle is based on wave-particle duality of electrons. The emitted electrons are high-energy matter having wavelength much smaller than that of light and this allows for the resolution of smaller objects. Moreover, the electrons interact with samples in various ways and this allows for the determination of detailed information about them. | Electron microscopy is a process of obtaining images using electrons and is frequently used when the magnification required is much larger than what can be achieved by light microscopes, i.e., the particles to be monitored are smaller than the wavelength of the visual light (< 400 nm). It is based on wave-particle duality of electrons. The emitted electrons are high-energy matter having wavelengths much smaller than that of light and this allows for the resolution of smaller objects. Moreover, the electrons interact with samples in various ways and this allows for the determination of detailed information about them. |
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| The two main electron microscopic techniques available for nanocomposite imaging are the scanning electron microscopy (SEM) and transmission electron microscopy (TEM). | The two main electron microscopic techniques available for nanocomposite imaging are the scanning electron microscopy (SEM) and transmission electron microscopy (TEM). |
"Spliced" plagiarism: The fragment Mrs/Fragment 061 06 is from the same source as this sentence, followed by a portion from the Wikipedia in Mrs/Fragment 061 13, then this fragment, followed by another portion from the Wikipedia Mrs/Fragment 061 23. |
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| 5.4. Spectroscopic technique [240, 241]
Spectral techniques are generally used to probe the chemical make-up of macromolecular materials such as functional groups, structural conformation and component concentration. The main spectral techniques applied in polymer nanocomposite research are Fourier transform infra-red spectroscopy (FTIR), nuclear magnetic resonance (NMR) and ultraviolet (UV) spectroscopy. [Figure] Figure 5.3 EM Spectrum showing the range of frequencies and wavelength of radiation. Spectral techniques involve the interaction of molecules of a specimen or sample with electromagnetic (EM) radiation. It essentially monitors changes in energy states of molecules in response to EM radiation. Figure 5.3 shows the EM spectrum and the corresponding wavelength of the various radiations. Important is to understand the energy state of molecules when EM radiation is observed. Basically, when an atom or a molecule absorbs energy, it proceeds from the initial or ground state to a higher or excited state. These energy states are said to be quantumized and a particular value exists for each state. This could be related to the “spinning” of the sub-atomic particles, vibration of the chemical bonds, and so on. Fourier transform infra-red spectroscopy (FTIR) FTIR is a technique that utilizes the vibration response of molecules when exposed to infrared (IR) radiation. |
[page 307]
6.4 Spectroscopic Techniques Spectral techniques are generally used to probe the chemical make-up of macromolecular materials, such as functional groups, structural conformation, and component concentrations. The main spectral techniques applied in polymer nanocomposite research are Fourier [page 308] transform infra-red spectroscopy (FTIR), nuclear magnetic resonance (NMR), and ultraviolet (UV) spectroscopy. This section will outline these methods and review some studies from literature. [Figure] Figure 6.46: EM spectrum showing the range of frequencies and wavelength of radiation. The shaded region is that of visible light Spectral techniques involve the interaction of molecules of a specimen or sample with electromagnetic (EM) radiation. It essentially monitors changes in energy states of molecules in response to EM radiation. Figure 6.46 shows the EM spectrum and the corresponding wavelengths of the various radiations. Of particular importance is to understand the energy “states” of molecules when EM radiation is absorbed. Basically, when an atom or molecule absorbs energy, it proceeds from the initial or ground state to a higher or excited state. These energy states are said to be quantized and a particular value exists for each state. This could be related to the “spinning” of the nucleus, vibration of the bonds, and so on. [...] 6.4.1 Fourier Transform Infra-Red (FTIR) Spectroscopy FTIR is a technique that utilizes the vibrational response of molecules when exposed to infrared (IR) radiation. |
The text and the figures are from different sources: The text is from Bhattacharya et al. 2008, the figures in the dissertation are edited versions of figures from the Wikimedia Commons http://commons.wikimedia.org/wiki/File:EM_spectrum.svg?uselang=en. There is no source for either the text or the figures given. |
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| The main thermal techniques are differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), dynamic mechanical analysis (DMA) and heat distortion temperature (HDT). Thermal analysis is based on the detection of changes in the heat content (enthalpy) or the specific heat of a sample with temperature.
5.5.1. Differential Scanning Calorimetry (DSC) Differential scanning calorimetry is a thermo-analytical method that measures the difference between the amount of heat necessary to raise the temperature of sample and reference. It is used to study thermal transitions of a polymer. As thermal energy is supplied to the sample, its enthalpy increase and the temperature rises by an amount determined by the specific heat of the sample. The specific heat of the material changes slowly with temperature in a particular physical state, but alter sharply or discontinuously when a change of the state of the matter takes place. Apart from increasing the sample temperature, the supply of thermal energy may also induce physical or chemical changes in the sample (e.g. melting or decomposition) accompanied by a change in enthalpy in the form of the latent heat of fusion, heat of reaction, or others. Such enthalpy changes may be detected by thermal analysis and can be related to the processes occurring in the sample. |
The main thermal techniques are differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), dynamic mechanical analyzer (DMA), heat distortion temperatures (HDT), and cone calorimetry. Thermal analysis is based on the detection of changes in the heat content (enthalpy) or the specific heat of a sample with temperature.
6.7.1 Differential Scanning Calorimetry (DSC) DSC is a technique which is part of a group of techniques called thermal analysis (TA). As thermal energy is supplied to the sample, its enthalpy increases and the temperature rises by an amount determined by the specific heat of the sample. The specific heat of a material changes slowly with temperature in a particular physical state, but alters sharply or discontinuously when a change of state takes place. Apart from increasing the sample temperature, the supply of thermal energy may also induce physical or chemical changes in the sample (e.g., melting or decomposition) accompanied by a change in enthalpy in the form of the latent heat of fusion, heat of reaction, or others. Such enthalpy changes may be detected by thermal analysis and can be related to the processes occurring in the sample. |
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| The presence of particle adds some complexity to the thermal behavior of the polymeric matrix. One of the most common effects is that the silica particle could serve as a nucleating agent, thus providing a large number of nucleation sites and allowing the polymer to crystallize at higher temperatures. This contributes to a change in the morphology of the system and in some cases, depending on the processing condition, a phase change occurs. | The presence of clay adds some complexity to the crystallization behavior of the polymeric matrix. One of the most common observations is that the clay could serve as a nucleating agent, thus providing a large number of nucleation sites and allowing the polymer to crystallize at higher temperatures. This contributes to a change in the morphology of the system, usually reflected in a larger number of smaller crystallites per unit volume. In some cases, depending on processing conditions, a phase change occurs. |
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| Crystallization kinetics and the morphology of crystallized products are strongly influenced by cooling rate, system pressure and the presence of particles. Melting and crystallization of crystalline polymers generally occurs over a range of temperature, because of the presence of a distribution of molecular weights and the mixed crystalline/amorphous phase in the sample. Polymer crystals occur in a variety of crystallite sizes and phases (e.g. α, β, γ, etc.). These phases may exhibit different melting/crystallization temperature. | [S. 109]
Crystallization kinetics and the morphology of crystallized products are strongly influenced by cooling rate, system pressure and the presence of clay. [S. 110] Melting and crystallization of crystalline polymers generally occur over a range of temperatures, because of the presence of a distribution of molecular weights and the mixed crystalline/amorphous phases in the sample. Polymer crystals occur in a variety of crystallite sizes and phases (e.g., α, β, γ, etc.). These phases may exhibit different melting/crystallization temperatures. |
The source is given on page 103 for the figure. |
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