Beitr�ge zur Kenntnis des Deformationsmechanismus und der Feinstruktur der Hydratzellulose

Hermans, P. H.; Platzek, P.

doi:10.1007/bf01518890

Cited by 280 publications

(100 citation statements)

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“…11 In the limit of perfect orientation, independent of the direction, this quantity will yield a value of 1, whereas 0 reflects a randomized orientation state (i.e., isotropic). In the analysis program, the azimuthally integrated dataset is split into four equal segments whose minimum intensity occurs at zero radians and whose maximum intensity occurs at /2.…”

Section: X-ray Scattering and Data Analyses Of Injectionmolded Plaquesmentioning

confidence: 98%

Characterization of the skin orientation of thermotropic liquid‐crystalline copolyester moldings with near‐edge X‐ray absorption fine structure

Bubeck

Thomas

Rendon

et al. 2005

J of Applied Polymer Sci

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ABSTRACT:The process of injection-molding net-shape parts from thermotropic liquid-crystalline polymers results in a skin-core macrostructure. The underlying orientation in the core and the skin may differ both in magnitude and direction. A combination of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and two-dimensional wide-angle X-ray scattering (2D WAXS) in transmission was used to characterize the orientation in injection-molded plaques fabricated from thermotropic liquid-crystalline copolyesters based on either 4,4Ј-dihydroxy-␣-methylstilbene or 6-hydroxy-2-naphthoic acid/6-hydroxybenzoic acid. NEXAFS is presented as a noninvasive in situ means of determining surface layer orientation that samples to a depth of as little as 2 nm and does not require slicing or ultramicrotoming of the samples. The effects of various processing conditions on the surface orientation in the region of the centerline of square injection-molded plaques are presented and discussed. Comparisons are made between orientation parameters obtained by 2D WAXS in transmission, which is dominated by the microstructure in the core, and the NEXAFS technique.

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Section: X-ray Scattering and Data Analyses Of Injectionmolded Plaquesmentioning

confidence: 98%

Characterization of the skin orientation of thermotropic liquid‐crystalline copolyester moldings with near‐edge X‐ray absorption fine structure

Bubeck

Thomas

Rendon

et al. 2005

J of Applied Polymer Sci

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“…Another interesting example is shown in Figure 14, where the smectic layer spacing of the nonchiral compound 3M 8422 (see Table 2) is compared to the layer spacing that would be expected according to Equation (8) when the optically observed tilt angle is taken into account. [63] The comparison clearly illustrates that the layer shrinkage actually occurring in this de Vries material is far smaller than the shrinkage which has to be expected by the classic picture of "tilting rodlike molecules".…”

Section: The Modern Picture Of the "De Vries" Transitionmentioning

confidence: 99%

Current Topics in Smectic Liquid Crystal Research

2006

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Interest in the smectic liquid-crystalline state of matter received a substantial boost with the discovery by Meyer in the mid-1970s that a chiral smectic C (SmC*) phase exhibits a spontaneous electric polarization, and with the subsequent demonstration by Clark and Lagerwall of the surface-stabilized SmC* ferroelectric liquid crystal at the beginning of the 1980s. Since then, chiral smectic phases and their plethora of polar effects have dominated the research in this field, which today has reached a mature state where the first commercial microdisplay applications are now shipping in millions-per-year quantities. In this Review we discuss some of the topics of highest interest in current smectic liquid crystal research, and address application-relevant research (de Vries-type tilting transitions without defect generation and high-tilt antiferroelectric liquid crystals with perfect dark state) as well as more curiosity-driven research (the nature and origin of the chiral smectic C subphases and their intermediate frustrated states between ferro- and antiferroelectricity).

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“…Hermans and Plazek, 38 and subsequently F. Muller, 39 proposed a measure of the average orientation of polymer chains relative to the axis of a fiber in which there is complete molecular symmetry around the axis. Muller formulates this as…”

Section: Structure Characterization Of Fibersmentioning

confidence: 99%

Structure development in melt spinning of poly(ethylene‐co‐octene) filaments with various comonomer contents

Shan

White

2004

J of Applied Polymer Sci

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An experimental study of the spinnability and the variation in crystallinity and orientation of melt spinning of poly(ethylene-co-octene) with different contents of comonomers was carried out. The spinning behavior of these polymers was investigated under different drawdown ratios and temperatures and correlated to spinline stress. The melt-spun filaments were characterized by wideangle X-ray diffraction birefringence, and differential scanning calorimetry. S-1 is a high-density polyethylene and S-2, S-3, and S-4 have 16, 22, and 38 wt % octene. An orthorhombic unit cell was found in all four polymers, but a dominant hexagonal structure (perhaps mesophase) was found for the highest octene level (S-4). The orientation factors for the a-, b-, and c-axis of the orthorhombic crystal structure and a-axis of the hexagonal phase were then calculated. The crystalline orientation behavior of the lower octene copolymers (S-1, S-2, and S-3) are similar and can be represented as a "rownucleated" structure. However, the orientation behavior of S-4 was different. The uniaxial mechanical properties were also measured. The Young's modulus and tensile strength generally increased with birefringence for all polymers. With increasing content of octene, the Young's modulus showed a decrease from semicrystalline thermoplastic toward an elastomer.

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Beitr�ge zur Kenntnis des Deformationsmechanismus und der Feinstruktur der Hydratzellulose

Cited by 280 publications

References 0 publications

Characterization of the skin orientation of thermotropic liquid‐crystalline copolyester moldings with near‐edge X‐ray absorption fine structure

Characterization of the skin orientation of thermotropic liquid‐crystalline copolyester moldings with near‐edge X‐ray absorption fine structure

Current Topics in Smectic Liquid Crystal Research

Structure development in melt spinning of poly(ethylene‐co‐octene) filaments with various comonomer contents

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