Papers by Keyword: WAXS

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Authors: Paulo E. Lopes, William T. Pennington, Michael S. Ellison
Abstract: Polymer crystalline regions can be characterized by wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS). The in-situ study of isotactic polypropylene with measurement of wide angle and small angle X-ray scattering (WAXS and SAXS), at varying distances from the exit of the extruder have been successfully completed using an X-ray system with a standard X-ray source. The processing conditions, used were: 50, 100, 200 and 400m.min-1 for the take up speed, 0.3, 0.6, and 1.2 cm3min-1hole-1 for the melt flow rates, and a spinning temperature of 220°C. These experimental conditions produced draw down ratios ranging from 33 up to 1058. The X-ray characterization was carried in-situ at 15, 30, 45 and 60 cm from the exit of the spinneret and also ex-situ. The results obtained show the crystallinity index and the crystalline orientation to increase for the higher draw down rates, as expected under draw induced crystallization conditions, and a logarithmic relationship was observed within the experimental conditions used in this work. This communication reports the relationship between the crystallinity, crystalline orientation and lamellar long period and draw down ratio along the spin line.
572
Authors: Amornrat Klaewklod, Vimon Tantishaiyakul, Tanatchaporn Sangfai, Namon Hirun, Supagorn Rugmai
Abstract: The evaluation of PEG as a gelation solvent for an organogel based on β-cyclodextrin (β-CyD) was investigated using principal component analysis (PCA). The test tube tilting method was performed to examine the gel formation experimentally. The important descriptors used in the PCA included the Hansen partial solubility parameters. LogP may be able to be used as an additional descriptor for this system. According to PCA analysis, PEG was in a cluster of gelation solvents. Subsequently, various PEG liquid state grades were tested for their ability to gel the system and PEG400 was found to be able to produce a gel. This verifies that PCA can be successfully used to evaluate the role of PEG. Accordingly, this PCA method may be an effective tool to evaluate the role of any solvent for other low molecular weight gelators (LMWGs). Afterwards, the optimal components in the system were explored, and it was found to be 0.1M β-CyD, 0.5M K2CO3 in PEG400. Based on WAXS, the gel fiber of this organogel was demonstrated to be amorphous. This forming organogel will be further characterized in details and investigated for use in a drug delivery system.
133
Authors: Marcin Bączek, Czesław Ślusarczyk, Jan Broda
Abstract: The effects of processing conditions on the structure of polypropylene fibrillated fibres were studied using a combination of wide- and small-angle X-ray scattering methods. In particular the impact of selected stages of processing on the crystalline and lamellar structure of PP were analyzed. It was stated that crystalline phase is built from α crystals. The crystallinity index as well as the Herman orientation factor of the crystalline phase is found to have a correlation only with the draw ratio of the PP film. The lamellar structure also changes with the draw ratio.
439
Authors: G.R. Mitchell, M. Belal, F.J. Davis, D.E. Elliott, M. Kariduraganavar, S.D. Mohan, R.H. Olley, Sujat Sen
Abstract: We use a combination of microscopy, x-ray scattering and neutron scattering to show how structure develops in micro and nano-size polymer fibres prepared by electrospinning. The technique has been applied to a range of different polymers, an amorphous system (polystyrene), a crystallisable polymer (poly-ε-caprolactone), a composite systems (polyethylene oxide or poly vinyl alcohol containing polypyrrole) and consider the possibility of self assembly (gelatin).
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Authors: Małgorzata Rabiej
Abstract: Most frequently, the degree of crystallinity of polymers is determined using Wide Angle X-ray Diffraction (WAXD) technique. The method consists in the resolution of WAXD diffraction curve of a polymer into individual crystalline peaks and amorphous halo. This work presents a procedure, which was elaborated to help in a quick determination of the angular positions of crystalline peaks present in the diffraction curve of investigated polymer. The positions of peaks are determined using numerical differentiation. Using these data the computer program WAXSFIT identifies investigated polymer and prepares a set of starting parameters which are used in the calculations of the degree of crystallinity.
189
Authors: Hai Juan Kong, Peng Yang, Cui Qing Teng, Ahmed M.S. Dawelbeit, Mu Huo Yu
Abstract: High modulus Poly (p-phenyleneterephalamide)(PPTA) fibers was prepared by heat drawing process, in which the fibers rearranged their structures for further improvements in their crystalline perfection, crystal line orientation. The modulus of PPTA fibers could be improved when fibers treated in an appropriate condition. The influences of heat treating time on the structures of the fibers and their properties were investigated by using two-dimensional wide-angle scattering (WAXS).
71
Authors: Júlio C. Viana, João F. Mano, Zlatan Z. Denchev, Maria Jovita Oliveira, Maria Clara Cramez
Abstract: In this work, the structural evolution and damage of PET during stretching is assessed by wide- and small-angle X-ray scattering (respectively, WAXS and SAXS) experiments in specimens pre-deformed at different strain levels (ex-situ characterization). Injection moulded PET rectangular tensile specimens were stretched (at 2 mm/min) into the plastic domain in a universal test machine at different strain levels at room temperature. The structure of the central zone of the deformed specimens was then characterized by WAXS and SAXS experiments using an X-ray synchrotron source. PET was initially (before stretching) amorphous. A strong molecular orientation in the stretching direction is quickly developed for the initial plastic deformation levels, evidenced by strong equatorial WAXS reflections. This orientation rapidly levels off, remaining constant during further stretching. The WAXS patterns are accompanied with no reflections on SAXS, evidencing a local ordering phenomenon, typical of nematic liquid-crystalline structures. The SAXS patterns evidence the occurrence of some voiding in the cold drawing regime just after yielding. These anisotropic voids are oriented perpendicular to the stretching direction, as in a craze-like structure. The void size drastically increases at the onset of the strong strain hardening behaviour.
1583
Authors: Mark R. Terner, Peter Hedström, Jonathan Almer, J. Ilavsky, Magnus Odén
Abstract: Residual stresses and microstructural changes during phase separation in Ti33Al67N coatings were examined using microfocused high energy x-rays from a synchrotron source. The transmission geometry allowed simultaneous acquisition of x-ray diffraction data over 360° and revealed that the decomposition at elevated temperatures occurred anisotropically, initiating preferentially along the film plane. The as-deposited compressive residual stress in the film plane first relaxed with annealing, before dramatically increasing concurrently with the initial stage of phase separation where metastable, nm-scale c-AlN platelets precipitated along the film direction. These findings were further supported from SAXS analyses.
619
Authors: K. Jokela, Sz. Galambosi, M. Karjalainen, M. Torkkeli, Ritva Serimaa, V. Eteläniemi, S. Vahvaselkä, M. Paronen, F. Sundholm
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