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Search query: semicrystalline polymers
31 articles match your search "semicrystalline polymers"Results 1 to 10, sorted by relevance:
research papers
This work presents a new optimization procedure, elaborated for the decomposition of wide-angle X-ray diffraction curves of semicrystalline polymers, based on the particle swarm optimization method, one of the most effective artificial intelligence methods. It is shown that the effectiveness and convergence of the elaborated system are better than the related parameters of other algorithms.
research papers
This work presents a hybrid immune–evolution strategy algorithm which is a combination of two methods of artificial intelligence – evolution strategies and an immune algorithm – with the classical method of Rosenbrock. The system can be successfully used for decomposition of the wide-angle X-ray diffraction curves of semicrystalline polymers into crystalline peaks and amorphous halos.
research papers
Processes for forming products from synthetic polymers often yield materials whose morphology is of low (orthorhombic, monoclinic, etc) symmetry. Characterizing such morphology by means of small-angle scattering (SAS) requires the mapping of the full three-dimensional scattering pattern from such materials. This requires special protocols in SAXS (small-angle X-ray scattering) or SANS (small-angle neutron scattering) experiments. SAS patterns from such experiments usually contain contributions from more than one scattering mechanism. In the case of semicrystalline polymers we have found that recording SAS patterns as a function of temperature allows the analyst to separate contributions arising from the two-phase morphology from those attributable to other effects such as voids and long-range molecular correlations. The synchrotron SAXS observations presented here extend our previous analysis of temperature-induced contrast variation in two-dimensional SAS patterns to two interesting three-dimensional cases.
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Lamellar thin films are an important class of soft materials. For such systems, grazing-incidence scattering with an area detector close to the incident plane is simulated.
research papers
The in situ vapor sorption technique is used to overcome the fundamental limitation of negligible neutron scattering contrast in semicrystalline polymers and to demonstrate that vapor selectively diffuses into the amorphous phase.
research papers
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Full pattern analyses of small-angle X-ray and neutron scattering data with both discrete reflections and central diffuse scattering are presented. Data with both equatorial streaks and two- and four-point reflections can be fitted in elliptical coordinates with relatively few parameters.
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The image analysis of TEM micrographs shows a quantitative correlation with SAXS measurements of the characteristic distances in semi-crystalline polymers.
research papers
It is shown that textures with double-axis averaging similar to the a-texture, or Keller-Machin Type I texture, are not specific to semicrystalline polymers exhibiting twisted lamellar growth; the same texture is observed in extruded fibers of a typical discotic molecule, trans-diC60-Zn porphyrin. The characteristic `comma'-like azimuthal intensity profiles of the non-equatorial diffraction peaks in two-dimensional X-ray patterns are described using a simple analytical model, which shows good agreement with experiment.
research papers
The methods used to estimate chord-length distributions from small-angle scattering data assume a structure made up of spatially uncorrelated and convex regions. Significant errors follow from applying these methods outside of their range of validity.
research papers
Energy-dispersive small-angle X-ray scattering experiments on protein solutions, micelles, semicrystalline polymers and metal oxides are discussed to illustrate the limits and the potentialities of this technique.
