dc.contributor.advisor Fossum, Jon Otto dc.contributor.advisor Balzano, Luigi dc.contributor.advisor Knaapila, Matti dc.contributor.author Hansteen, Marie dc.date.accessioned 2019-09-11T09:57:52Z dc.date.created 2018-07-16 dc.date.issued 2018 dc.identifier ntnudaim:19290 dc.identifier.uri http://hdl.handle.net/11250/2615601 dc.description.abstract This thesis reports on the effect of processing conditions, including the presence and chemical nature of solvents, on the structure, morphology, and properties of concentrated ultra-high molecular weight polyethylene (UHMWPE) in solutions as it passes through the gel-spinning process. This thesis contains two parts, investigating the first and second part of this process: dissolution and drawing. Part I presents an in-situ small- and wide angle X-ray diffraction study (SAXS/WAXS) of UHMWPE dissolved in different solvents (decalin, paraffin oil, or stearic acid). Each sample is heated to temperatures above its melting point, kept constant, and subsequently cooled down. WAXS data during heating and cooling illustrate the melting and crystallization procedures of UHMWPE showing the degree of crystallinity and melting of the crystal lamellae, and thermal expansion of the unit cell. We find the following results not reported in the prior art: UHMWPE within a solvent follows the same trends as reported for pure semicrystalline materials. These processes are qualitatively independent on solvent, concentration, and type of polymer. Although, the kinetics (the speed) is clearly dependent on the solvent. This is observed as a change in the crystallization (T$_{c}$) and melting (T$_{m}$) temperatures. SAXS data from the high angle regime (in this investigation: s$^{2}$ = 0.006 - 0.0125 \AA$^{-2}$, q = 0.487 - 0.702 \AA$^{-1}$) indicate density fluctuations within the isotherm region where the material is interpreted as a one phase liquid. We observe density fluctuations only at the atomistic length scale, i.e. within the chemical composition of the solvent molecules with respect to that of the polymer chains. Hence, we observe homogeneous mixtures regardless of the sample composition, which is a desirable verification of the first part of the production process. As a future study, we suggest performing SAXS at lower angles or light scattering experiments to observe whether there are density fluctuations at a larger length scale. Part II presents the production steps after the melt enters the spinneret and subsequently the quench. This involves characterization of structural homogeneities developing upon drawing to the stages of un-, partially, and fully drawn yarns (denoted as UDY, PDY, and FDY) of UHMWPE fibers seen in relation to material properties, as investigated by WAXS and Raman spectroscopy. A clear skin-core structure of the fiber filaments is revealed and is proposed to be the limiting feature for the breakpoint of the filament. We propose a model for the development of the structure and morphology of UHMWPE fiber filaments by combining these observations with results from previous investigations and complementing theories of tie chains and shish-kebab. en dc.language eng dc.publisher NTNU dc.subject Fysikk og matematikk, Teknisk fysikk en dc.title The Development of Structural and Morphological Features during Gel-Spinning of UHMWPE Fibers en dc.type Master thesis en dc.source.pagenumber 108 dc.contributor.department Norges teknisk-naturvitenskapelige universitet, Fakultet for naturvitenskap,Institutt for fysikk nb_NO dc.date.embargoenddate 10000-01-01
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