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    Wyświetlanie 1-3 z 3
    Tytuł:
    Shear-Induced Molecular Orientation of Compression Moulded PE-HD Sheets
    Autorzy:
    Chomiak, Monika
    Stabik, Józef
    Powiązania:
    https://bibliotekanauki.pl/articles/2201822.pdf
    Data publikacji:
    2022
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    PE-HD
    PE-HD sheets
    anisotropy
    molecular orientation
    mechanical properties
    compression moulding
    Opis:
    The article presents experimental results on orientation of polymer macromolecules in compression moulded high density polyethylene sheets. Properties anisotropy of thermoplastic films or sheets, that are usually formed in the extrusion process, causes deformation of thermoformed products and is a serious technological problem. One of the possible solutions of this problem is application of compression moulded sheets. The paper presents the results of tests of selected strength characteristics of compression moulded PE-HD sheets. A static tensile test was performed and Charpy impact strength was determined. Additionally Chrystler’s orientation test was executed. For comparison the same experiments were performed on extruded sheets. Samples were cut in directions perpendicular and parallel to the direction of polymer flow in pressing and extrusion processes. The obtained results indicate that the compression moulding technique allows the production of sheets that do not exhibit statistically significant anisotropy of the tested strength properties.
    Źródło:
    Advances in Science and Technology. Research Journal; 2022, 16, 4; 85--95
    2299-8624
    Pojawia się w:
    Advances in Science and Technology. Research Journal
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Properties of water hydrating the galactolipid and phospholipid bilayers: a molecular dynamics simulation study
    Autorzy:
    Markiewicz, Michał
    Baczyński, Krzysztof
    Pasenkiewicz-Gierula, Marta
    Powiązania:
    https://bibliotekanauki.pl/articles/1038986.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    molecular modelling
    hydrogen bonds
    water diffusion
    water dipole orientation
    inter-lamellar water
    Opis:
    Molecular dynamics simulations of 1,2-di-O-acyl-3-O-β-D-galactopyranosyl-sn-glycerol (MGDG) and 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) bilayers were carried out to compare the effect of the lipid head group's chemical structure on the dynamics and orientational order of the water molecules hydrating the bilayer. The effect of the bilayers on the diffusion of water is strong for the neighbouring water molecules i.e., those located not further than 4 Å from any bilayer atom. This is because the neighbouring water molecules are predominantly hydrogen bonded to the lipid oxygen atoms and their mobility is limited to a confined spatial volume. The choline group of DOPC and the galactose group of MGDG affect water diffusion less than the polar groups located deeper in the bilayer interface, and similarly. The latter is an unexpected result since interactions of water with these groups have a vastly different origin. The least affected by the bilayer lipids is the lateral diffusion of unbound water in the bilayer plane (x,y-plane) - it is because the diffusion is not confined by the periodic boundary conditions, whereas that perpendicular to the plane is. Interactions of water molecules with lipid groups also enforce certain orientations of water dipole moments. The profile of an average water orientation along the bilayer normal for the MGDG bilayer differs from that for the DOPC bilayer. In the DOPC bilayer, the ordering effect of the lipid head groups extends further into the water phase than in the MGDG bilayer, whereas inside the bilayer/water interface, ordering of the water dipoles in the MGDG bilayer is higher. It is possible that differences in the profiles of an average water orientation across the bilayer in the DOPC and MGDG bilayers are responsible for differences in the lateral pressure profiles of these bilayers.
    Źródło:
    Acta Biochimica Polonica; 2015, 62, 3; 475-481
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Molowa entropia orientacyjna i struktura cieczy zasocjowanych
    Molar orientation entropy and structure of the self-associated liquids
    Autorzy:
    Jadżyn, J.
    Świergiel, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/172403.pdf
    Data publikacji:
    2017
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    dipole molekularne
    przenikalność statyczna
    entropia orientacyjna
    ciecz
    wiązania wodorowe
    przejście fazowe ciecz izotropowa-nematyk
    molecular dipoles
    static permittivity
    orientation entropy
    liquids
    hydrogen bonds
    isotropic liquids to nematic phase transition
    Opis:
    Research on the structural effects of intermolecular interactions not only brings us closer to a better understanding the macroscopic properties of liquids, but also allows one to modify these properties. Intermolecular dipolar couplings and hydrogen bonds are the most common interactions in liquids leading to formation of multimolecular entities with various structures. The natural rival of these interactions is the thermal agitation of molecules (kT), which aims to destroy the emerging structures. In this paper we present an experimental method to estimate the way of molecular self-assembly resulting from the simultaneous action of kT and intermolecular interactions. The method is based on the study of dipolar orientation effects induced by an applied electric field. As an experimental source of the information on these effects is temperature derivative of the static permittivity of tested liquid. That derivative is proportional to the liquid entropy change due to the ordering action of the electric field on the molecular dipoles. Here, we present the experimental results on temperature dependence of the static permittivity and increment of the orientation entropy of liquids where the self-association process realizes with two ways: dipolar couplings and hydrogen-bonds.
    Źródło:
    Wiadomości Chemiczne; 2017, 71, 7-8; 517-532
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-3 z 3

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