Journal ArticleDOI
Chain Mobility in Polymer Systems: on the Borderline between Solid and Melt. 1. Lamellar Doubling during Annealing of Polyethylene
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In this paper, small-angle X-ray scattering (SAXS) and low-frequency Raman spectroscopy experiments have been performed to study the mobility and motion of polymer chains upon annealing in a temperature range close to but below the melting temperature.Abstract:
In-situ small-angle X-ray scattering (SAXS) and low-frequency Raman spectroscopy experiments have been performed to study the mobility and motion of polymer chains upon annealing in a temperature range close to but below the melting temperature. Ultrahigh molecular weight polyethylene, UHMW-PE, was taken as the model polymer, which was crystallized from solution. Regularly stacked lamellar crystals could be obtained after drying the solution-crystallized films. SAXS studies revealed that, upon heating above 110 °C, the lamellar thickness (long period) increases to twice the initial value. This quantum increase was confirmed by transmission electron microscopy (TEM). By means of in-situ low-frequency Raman spectroscopy it was observed that during heating a shift occurs in the longitudinal acoustic (LA) Raman frequency to lower values, indicative of an increase in the thickness of the crystalline core. The combined experimental observations indicate that thickening occurs via a mutual chain rearrangement be...read more
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Strength and toughness of crystalline polymer systems
TL;DR: The role of crystal plasticity in achieving high toughness is addressed in this article, where two possibilities of the modification of crystal thickness are described: increase in the crystal thickness and a reduction in the number of mobile dislocations in polymer crystals, and two examples of efficient toughening in multicomponent polypropylene systems connected with cavitation are described.
Journal ArticleDOI
Heterogeneity in polymer melts from melting of polymer crystals
Sanjay Rastogi,Dirk R. Lippits,Gerrit W. M. Peters,Robert Graf,Yefeng Yao,Hans Wolfgang Spiess +5 more
TL;DR: It is shown that through slow and carefully controlled melting such polymer crystals form a heterogeneous melt with more entangled regions, where the chains are mixed, and less entangled ones, composed of individually separated chains, which shows decreased melt viscosity and provides enhanced drawability on crystallization.
Journal ArticleDOI
Insights into polymer crystallization and melting from fast scanning chip calorimetry
TL;DR: Fast scanning chip calorimetry in its non-adiabatic version allows for heating and cooling at rates up to 106 K s−1, covering all polymer processing relevant rates as mentioned in this paper.
Journal ArticleDOI
Crystalline Structures, Melting, and Crystallization of Linear Polyethylene in Cylindrical Nanopores
TL;DR: The crystalline structures associated with melting and crystallization behaviors of monodisperse linear polyethylene confined in cylindrical nanopores were investigated by X-ray diffraction and differential scanning calorimetry as mentioned in this paper.
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Unprecedented High-Modulus High-Strength Tapes and Films of Ultrahigh Molecular Weight Polyethylene via Solvent-Free Route
TL;DR: Uncedented high-modulus high-strength tapes and films of ultra-high molecular weight polyethylene via solvent-free route as mentioned in this paper. But this is not the case for all tapes.
References
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Viscoelastic properties of polymers
TL;DR: In this article, the authors describe the nature of Viscoelastic behavior of polymeric systems and approximate relations among the linear Viscoels and approximate interrelations among the Viscelastic Functions.
Journal ArticleDOI
Reptation of a Polymer Chain in the Presence of Fixed Obstacles
TL;DR: In this paper, the authors studied possible motions for one polymer molecule P performing wormlike displacements inside a strongly cross-linked polymeric gel G. The topological requirement that P cannot intersect any of the chains of G is taken into account by a rigorous procedure: the only motions allowed for the chain are associated with the displacement of certain "defects" along the chain.
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Dynamics of concentrated polymer systems. Part 3.—The constitutive equation
Masao Doi,Sam F. Edwards +1 more
TL;DR: In this article, the rheological constitutive equation of a condensed polymer system is presented based on the primitive chain model presented in Parts 1 and 2, and it predicts a stress superposition law in the regime of nonlinear viscoelasticity.
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Longitudinal Acoustical Vibrations of Finite Polymethylene Chains
TL;DR: In this paper, the low-frequency Raman scattering spectra of finite polymethylene chains, observed utilizing laser excitation, show a band progression whose frequencies vary inversely and continuously as a function of chain length.