A polymer is rarely used as a pure material and the baseline physical, chemical and rheological properties such as molecular weight, strength, stiffness and viscosity are often modified by the addition of fillers or by blending with another polymer. However, as many polymers are immiscible, compatibilisation and graft processing polymer blends are very important techniques to increase miscibility of the blends as well as to improve chemical, physical and mechanical properties. Reactive extrusion, or melt-state processing, is one of the most appropriate techniques for improving polymer properties. Compatibilisation and graft polymer processing are often carried out under reactive extrusion conditions. This technique is an efficient approach because it is easy, inexpensive and has a short processing time. Although reactive extrusion has numerous advantages one of the limitations is degradation of the polymer under the high temperatures and mechanical stresses encountered. In the polymer industry, because of increasing customer demand for improved product quality, optimising the polymerisation process by decreasing product costs and controlling the reaction during polymerisation has become more important. It can be said that any method used for monitoring the polymerisation process has to be fast, accurate and reliable. Both in-line and on-line methods may be involved in in-process monitoring. The primary information from in-process monitoring is used for identifying and understanding molecular structure and changes, optimising and improving process modelling and understanding whether the process is under control. This also involves considering whether the products have the required properties. This thesis describes research in a number of aspects of melt processing of polymers, including examination of extruded products, an in situ spectroscopic study of the reaction of MAH and PP, a study of the melt processing of TPU, and a study of the use of nitroxide radicals as probes for degradation reactions. As mentioned previously, a suitable method for improving polymer properties is polymer blending. Starch is a hydrophilic biodegradable polymer which may be blended with other polymers to produce biodegradable products. In spite of its benefits, it is immiscible with most synthetic polymers, such as polyesters. The main technique for improving the miscibility of starch with the other polymer is a grafting reaction. The reactive extrusion technique was applied to the production of starch and polyester blends, the product of which was a biodegradable aliphatic polyester. In this process dicumyl peroxide (DCP) and maleic anhydride (MAH) were used as an initiator and cross-linker, respectively. Extruded samples were investigated by infrared microscopic mapping using the attenuated total reflectance (ATR) technique. Measurement of various band parameters from the spectra allowed IR maps to be constructed with semi-quantitative information about the distribution of blend components. IR maps were generated by measuring the band area ratio of O-H and C=O stretching bands which are related to starch and polyester, respectively. This was the first time this method has been used for understanding the homogeneity of a polymer blend system. This method successfully indicated that the polyester/starch blend was not a homogenised blend. It was concluded that to improve the homogeneity the reaction conditions should be modified. Another important compatibilisation reaction is the reaction between a polyolefin and MAH. This was investigated by combining a near infrared (NIR) spectrometer with a small laboratory scale extruder, a Haake Minilab. The NIR spectra were collected in situ during melt processing by the use of a fibre optic cable. In addition to this the viscosity of the polymer melt was measured continuously during processing through two pressure transducers within the Minilab extruder. The vinyl C-H stretch overtone of the MAH was clearly seen in the NIR spectra near 6100 cm-1 and diminished over time as the MAH reacted with PP. The spectra obtained were analysed by two techniques: principal component analysis (PCA); and peak area ratios. The peak area ratios were calculated using the =C-H first overtone of MAH with respect to the band observed between 6600 and 7400 cm-1. This band corresponds to a combination band of CH2 and CH3 in PP and was unchanged during the reaction. These data facilitated interpretation of the reaction kinetics and experiments at different temperatures allowed determination of the activation energy of the reaction. These results have thrown new light on the PP-MAH reaction mechanism. It was also shown that although the presence of DCP causes production of a high concentration of macro-radicals it does not have any effect on the rate and kinetics of the reaction. As mentioned previously, one of the limitations of reactive extrusion is degradation of the polymer under high temperatures and shear rates. Hindered amine stabilisers (HAS) are often used as inhibitors to control the thermal-oxidative degradation of polymers. They are used in various polymeric materials but were primarily developed for polyolefins, particularly PP. The stabilisation mechanism of HAS involves interaction firstly with the alkyl peroxyl radicals produced during oxidative degradation so that the hindered amine converts to the corresponding nitroxide. The nitroxide is then able to capture a carbon-centred radical and so retard the subsequent degradation chain reaction. 1,1,3,3- tetramethyldibenzo[e,g]isoindoline-2-yloxyl (TMDBIO) was used as a probe for investigation of PP during reactive extrusion conditions. The TMDBIO is a profluorescent compound that has been used previously to identify polymer degradation. In the radical form, there is no fluorescence since the unpaired spin on the nitroxide quenches the fluorescence of the phenanthrene moiety. When the radical is removed (by radical trapping or reduction) fluorescence is observed. As a result, the location and intensity of fluorescence can be used as a probe for identification of degradation and to determine the concentration of carbon-centred radicals produced during thermal or mechanical degradation such as occurs during reaction processing. This novel method shows that, the degradation of PP started at the early stage of processing. Also this method can be used as a useful technique to modify the processing conditions to decrease degradation of the polymer during processing. The second system investigated using in situ monitoring via the NIR fibre optic was the melt processing of a TPU nano-composite. This was the first time that the in situ monitoring of TPU nano-composite had been examined. In this investigation the effect of temperature during processing on the TPU molecular structure and rheological behaviour was again investigated. In addition, dispersion of clay nano-particles through the TPU matrix and rheological changes due to this was investigated. This investigation was successful in that it was found that several factors affected the viscosity of the nano-composite. However, to fully understand the degradation mechanism and viscosity changes further studies must be performed.

Thesis (Ph. D.)--University of Nevada, Reno, 2007. / "December, 2007." Includes bibliographical references (leaves 149-162). Online version available on the World Wide Web.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. Includes bibliographical references (leaves 467-476).

Thesis (Ph. D.)--University of Rhode Island, 2004. / Typescript. Includes bibliographical references (leaves 138-141).

No description available.

Please read the abstract in the front of the document. / Dissertation (MSc)--University of Pretoria, 2009. / Physics / unrestricted

No description available.

Includes bibliographical references. / A critical examination of the characteristic N-O vibrational frequencies of aromatic N-oxides questions the widely held assignment of αN-O (840cm⁻¹) and YN-O (47oon- 1). The present investigation supports the assignments of αN-O (470cm⁻¹) and γN-O (280cm⁻¹), with the assignment of the band at 840cm⁻¹ as being vring coupled with νN-O.

A thesis submitted to the Faculty of Science and Agriculture in fulfillment of the requirements of the Degree of Master Of Science in Physics in the Department of Physics at the University of Zululand, 2017 / Over the last decade, iThemba LABS has had an active research program that focuses on the spectroscopy of low lying positive parity bands [1–8], particularly the so-called β and γ vibrational bands, which are traditionally associated with the first excited Kπ = 0+ and Kπ = 2+ bands, respectively. Through this program, the nature of these bands has been studied extensively. However, despite this, the microscopic identity of these bands remains elusive in the transitional rare-earth region. This work seeks to give an insight on the microscopic nature of these bands by studying the spectroscopy of 162Yb. The data for the nucleus of interest (162Yb) was collected at iThemba LABS, using the 150Sm (16O, 4n) 162Yb fusion evapora- tion reaction. The γ rays emitted from the reaction products were detected using the AFRODITE γ ray spectrometer [9] equipped with escape-suppressed clover detectors. A total of 10 bands have been observed in this work. The DCO and polarization measurements have not only been used to confirm assignments that were made by previous in-beam works on well established structures [10–12] - but have also been instrumental in the assignment of spins and parities for the majority of newly established bands in 162Yb. Further, the current study has not only confirmed all the rotational structures reported by previous in-beam works but has also extended the level scheme of 162Yb by establishing 6 new bands. More importantly, a band built on the above- mentioned Kπ = 0+ excitation has been identified for the first time. In addition, for the first time in 162Yb, we also report rotational levels that form band structures of both the odd and even spin components of the Kπ = 2+ γ vibrational band.

<p> Three electronic absorption systems of the S2O molecule, each having discrete vibrational structure, were observed in the spectral region 2000 - 7400 Ȧ. Long pressure path lengths were used to observe very weak absorption bands. Two of these spectral systems have not been observed previously. Vibrational analyses of the spectral systems were made. The quasilinear character of the ground electronic state of S2O has been established.</p> / Thesis / Doctor of Philosophy (PhD)