Gitterstörungen in polyäthylen

Hosemann, Von Rolf; Wilke, W.

doi:10.1002/macp.1968.021180115

Cited by 129 publications

(55 citation statements)

References 18 publications

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“…Rao et al 43 The paracrystalline lattice structure analysis developed by Barton 116 is founded by Hosemann [117][118][119][120][121] . The defects in the crystal lattice can be improved by the possibility of lateral crystal growth (Axial crystal size) particularly along the hydrogen bonding direction occurring during the heat treatment of the PPTA fiber.…”

Section: Axial Crystal Size (L)mentioning

confidence: 99%

Microstructural developments of poly (p-phenylene terephthalamide) fibers during heat treatment process: a review

et al. 2014

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Poly (p-phenylene terephthalamide) fibers prepared by wet or dry-jet wet spinning processes have a notable response to very brief heat treatment (seconds) under tension. The modulus of the as-spun fiber can be greatly affected by the heat treatment conditions (temperature, tension and duration). The crystallite orientation and the fiber modulus will increase by this short-term heating under tension. Poly (p-phenylene terephthalamide) fibers have a very high molecular orientation (orientation angle 12-20°). Kevlar  and Twaron  fibers are poly (p-phenylene terephthalamide) fibers. This review reports for PPTA fibers the heat treatment techniques, devices and its process conditions. It reports in details the structural relationships between the fiber properties which are influenced by the heat treatment process. In particular, focused deeply on the effect of the crystal structure and the morphology of the fibers on the mechanical properties of PPTA fibers.

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Section: Axial Crystal Size (L)mentioning

confidence: 99%

Microstructural developments of poly (p-phenylene terephthalamide) fibers during heat treatment process: a review

et al. 2014

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“…The experimental procedure is described in detail in ref 2. According to the integral breadth (IB) method 4 based on the paracrystalline theory the IB of the 00 I reflection of the Cauthy type is given by (1) where Dw denotes the 'weight-average' crystallite size along the chain axis, c the averaged cdimension, g the longitudinal distortion parameter, and s 1 =2 sin BJ.1 .. Among the 001 reflections of PTEOX only two reflections 009 and 0018 can be used, since the 0027 reflection is too weak.…”

Section: Methodsmentioning

confidence: 99%

Wide-Angle X-Ray Scattering of Poly(tetroxocane) Obtained by Radiation-Induced Polymerization in the Solid State

Odajima

Ishibashi

Nakase³

et al. 1983

Polym J

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ABSTRACT:X-Ray scattering profiles of 009 and 0018 reflections of poly(tetroxocane) prepared by radiation-induced polymerization were investigated. It was confirmed that two types of crystallites coexisted in the polymers obtained by post-polymerization above 80°C: lamellar type crystallites with a longitudinal dimension of I 00 A and fibrillar crystals 250 A in crystallite size. The lamellar crystallites were less distorted than the fibrillar ones. Only fibrillar crystallites were found in samples polymerized below 80oC.KEY WORDS Poly(tetroxocane) I Wide-Angle X-Ray Scattering 1 Crystallite Size I Distortion Parameter I Lamellar Fibrils I Melting Behavior I In a preceding paper/ the fibrillar structure of a poly(tetroxocane) (PTEOX) sample prepared by the radiation-induced post-polymerization of tetroxocane above 80°C was investigated by small-angle X-ray scattering (SAXS) and thermal analysis. A broad discrete reflection corresponding to a Bragg spacing of about 500 A was observed on the meridian in addition to the reflection associated with a long spacing of 100 A. It was ascertained that the former reflection was due to the density difference between void and fibrillar crystals stacked alternately in the direction of the c-axis, while the latter was due to the lamellar crystals probably situated between the fibrillar ones. 2 In this paper, wide-angle X-ray scattering (W AXS) of PT EOX is investigated in order to clarify the lamellar and fibrillar structures of PT EOX polymerized at various temperatures.

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“…A symmetrical-reflection technique was employed to record the diffraction intensity curves, which were detected by a scintillation counter with a pulse-height analyzer. Intensities were counted at 0.05° intervals in Bragg angle (20) and the counting period was 80 sec. Circular dichroism was measured by using a JASCO Automatic Recording Spectropolarimeter Model J-5.…”

Section: Methodsmentioning

confidence: 99%

“…The symmetrical-reflection method is profitable for obtaining a profile of the equatorial reflections of cast films having a planar orientation. 20 But this method has some difficulties in the range of a small diffraction angle. Figure 7 shows the plots of the integral breadth of the (100) reflection against the casting temperature, where the instrumental broadening was corrected by use of the (111) reflection of the silicon powder poured on the film surface.…”

Section: Influence Of Casting Temperature On Structure Of Pmdg Filmsmentioning

confidence: 99%

Structure and Mechanical Properties of Poly(γ-methyl glutamate) Films. II.

Watanabe

Naka

Watanabe

et al. 1978

Polym J

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ABSTRACT:A series of poly(r-methyl o-glutamate) (PMDG) films with the different structures were systematically prepared from dichloromethane (DCM)-N, N-dimethylformamide (DMF) solutions. The structures of these films were classified into three types, vix., phase I, phase M, and phase C as obtained in a previous work from DMF, 1, 2-dichloroethane and DCM, respectively. Observation of the PMDG films cast from ch!oroform-DMF solutions, showed that phase C arises from the phase which consists of the cholesteric liquid crystal structure, and it was assumed that the crystallites in phase C should be divided into mosaic blocks. Three mechanical dispersions were observed at 160, 190°C, and above 200°C. The a1 dispersion (at 160°C) was associated with the molecular relaxation in phase I, and further, the a 3 dispersion (above 200°C) was related to the molecular motion of a-helices in phase M with the cholesteric twisted structure. For the a2 dispersion (at 190°C) commonly observed for phase C, two relaxation mechanisms are discussed: the molecular motion of ahelices in phase C and the mutual displacement of the neighboring crystallites. The PMDG films cast from m-cresol at various temperatures and the PMDG-poly(r-methyl L-glutamate) (PMLG) blend films cast from chloroform solutions, showed a remarkable shift of a 2 loss peak temperature. To explain this shift in peak temperature, the latter mechanism seems reasonable for the a 2 dispersion.KEY WORDS Poly(r-methyl glutamate)/ Casting History/ Cast Film/ Mechanical Dispersion / X-Ray Diffraction / Depending on the solvent and polypeptide concentration, a polypeptide molecule may exist in a number of conformations in solution. 1 Solvents are categorized into random coil and helical types. The random coil solvents are generally very polar and form strong hydrogen bonds with the polypeptide molecules. Dichloroacetic acid (DCA) and trifluoroacetic acid (TFA) are random coil solvents for many polypeptides in dilute solution. Most chlorinated hydrocarbons such as chloroform and DCM, with DMF and m-cresol, favor formation of the helical form of the polypeptide. chain structure has been observed in the films swollen in formic acid and in crystals precipitated from dilute solution containing formic acid. 2 This structure is also obtained from TFA or DCA solution, depending on the casting velocity. 3 Thus, when the films are cast from random coil solvents, the chain conformation in the films is not only in the helical form, but also partially in the /3-chain form.Poly(r-methyl glutamate) is known to be soluble also in the coil form in such solvents as DCA and TF A, and in the helical form in helicogenic solvents such as m-cresol and chloroform. However, when films are prepared from random coil solvents, the chain conformation in the films is mainly in the helical form. On the other hand, the /3-No conformational change is observed when the films are cast from the helicogenic solvents. Thus, in this solvent system, the association or aggregation of a-helices 4 -6 is of interest. In a...

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Gitterstörungen in polyäthylen

Cited by 129 publications

References 18 publications

Microstructural developments of poly (p-phenylene terephthalamide) fibers during heat treatment process: a review

Microstructural developments of poly (p-phenylene terephthalamide) fibers during heat treatment process: a review

Wide-Angle X-Ray Scattering of Poly(tetroxocane) Obtained by Radiation-Induced Polymerization in the Solid State

Structure and Mechanical Properties of Poly(γ-methyl glutamate) Films. II.

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