The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform
R.r. Zahran - One of the best experts on this subject based on the ideXlab platform.
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Analysis of the thermal expansion behavior of oriented Polyoxymethylene sheets
Polymer Engineering and Science, 1996Co-Authors: R.r. Zahran, S. S. Shenouda, Y. A. El-tawil, A. El-kayarAbstract:The applicability of the molecular composite model is extended to include the analysis of the thermal expansion behavior of oriented (anisotropic) Polyoxymethylene. The model accounts for changes in the morphological and structural aspects of Polyoxymethylene during solid state-induced orientation. The results are reported and analyzed in terms of three-dimensional surfaces. Apart from the effect of temperature, it has been found that the crystalline phase orientation distribution, A, is the most crucial parameter affecting the thermal expansion behavior of anisotropic Polyoxymethylene followed by the volume fraction crystallinity. The size and the geometry of the crystalline phase have negligible effects on the thermal expansion behavior of oriented Polyoxymethylene. Above the glass-transition temperature, a minimum in the transverse thermal expansion coefficient is exhibited in the vicinity of A = 2 for volume fraction crystallinities ≤0.75. It is sufficient to align 75% of the crystallites with their c-axis at ±10° to the draw direction, to attain the ultimate degree of anisotropy in the thermal expansion behavior of oriented Polyoxymethylene sheets.
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Stiffness of Polyoxymethylene whiskers/Polyoxymethylene resin composite films
Polymer Engineering and Science, 1991Co-Authors: R.r. ZahranAbstract:This paper presents a refinement of an erroneous, recently published analysis of the mechanical properties of Polyoxymethylene (POM) whisker/POM resin composite system. Furthermore, it extends the applicability of the molecular composite model to isotropic POM resins. It is shown that using the Halpin-Tsai equation, coupled with the laminate theory, is highly superior to using the Nielsen-generalized Halpin-Tsai equation for predicting the modulus of the whisker/resin system. The comparison between the experimental tensile modulus data and the predicted results, as functions of the whisker volume content, yields a good agreement to better than 15%.
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Thermal dimensional stability of isotropic Polyoxymethylene
Polymers for Advanced Technologies, 1991Co-Authors: R.r. Zahran, Abir A. AbolmagdAbstract:A parametric mapping analysis of the effect of various structural and morphological parameters on the thermal dimensional stability of Polyoxymethylene is highlighted. The molecular composites model is found to describe adequately the expansional behavior of isotropic Polyoxymethylene. The thermal expansivity is highly sensitive to the level of crystallinity followed by the transverse dimension of the crystallites. The longitudinal dimension of the crystallites, however, is not effective in altering the expansion behavior of isotropic Polyoxymethylene. When comparing the model calculations with experimentally published data, an agreement of better than 15% is observed.
Masamichi Kobayashi - One of the best experts on this subject based on the ideXlab platform.
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Vibrational spectroscopic study on poly(ethylene oxide) crystals
Polymer, 1990Co-Authors: Masaki Shimomura, Yoshikazu Tanabe, Yuka Watanabe, Masamichi KobayashiAbstract:Abstract It has been found for Polyoxymethylene that differences in morphological structure cause remarkable frequency changes for some infra-red-active vibrational modes. In relation to this phenomenon, the vibrational spectra of poly(ethylene oxide) were investigated on two samples with different morphologies, a well drawn film and a solution-grown lamellar crystal. The A2 bands of the solution-grown crystal shifted towards the high-frequency side, while the other bands, A1 and E1, remained at the same positions as those of the drawn film. It was concluded that the spectral change is due to the same mechanism as in Polyoxymethylene.
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Vibrational spectroscopic study on low-molecular-weight Polyoxymethylene diacetate
Polymer, 1990Co-Authors: Masaki Shimomura, Masatoshi Iguchi, Masamichi KobayashiAbstract:Abstract Infra-red and Raman spectra of low-molecular-weight Polyoxymethylene diacetates are investigated and compared with those of the extended- and folded-chain crystals of high-molecular weight trigonal Polyoxymethylene. Some bands assignable to the A2 symmetry species shift towards the high-frequency side, as was found in the folded-chain crystal. The infra-red spectral changes for the extended-chain crystal, folded-chain crystal and low-molecular-weight Polyoxymethylene diacetates that occur on mechanical deformation and melt crystallization are also discussed. A minor shift of Raman bands of the low-molecular-weight Polyoxymethylene diacetates was also found and discussed.
Dang Xiao-fei - One of the best experts on this subject based on the ideXlab platform.
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Advances in the Synthesis of Polyoxymethylene
Polymer Bulletin, 2011Co-Authors: Dang Xiao-feiAbstract:This paper reviewed research achievements of initiator and comonomer in the preparation of Polyoxymethylene,and then summarized their research progress in structure and performance.It was pointed out that we must synthesize high performance Polyoxymethylene such as introducing comonomers with sidegroups in order to improve toughness and thermal stability of Polyoxymethylene.By optimizing molecular structure of comonomer,adjusting the amount of comonomer,we could gain high performance Polyoxymethylene resin to adapt to the high speed,high temperature and high pressure working environment.
Masaki Shimomura - One of the best experts on this subject based on the ideXlab platform.
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Vibrational spectroscopic study on poly(ethylene oxide) crystals
Polymer, 1990Co-Authors: Masaki Shimomura, Yoshikazu Tanabe, Yuka Watanabe, Masamichi KobayashiAbstract:Abstract It has been found for Polyoxymethylene that differences in morphological structure cause remarkable frequency changes for some infra-red-active vibrational modes. In relation to this phenomenon, the vibrational spectra of poly(ethylene oxide) were investigated on two samples with different morphologies, a well drawn film and a solution-grown lamellar crystal. The A2 bands of the solution-grown crystal shifted towards the high-frequency side, while the other bands, A1 and E1, remained at the same positions as those of the drawn film. It was concluded that the spectral change is due to the same mechanism as in Polyoxymethylene.
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Vibrational spectroscopic study on low-molecular-weight Polyoxymethylene diacetate
Polymer, 1990Co-Authors: Masaki Shimomura, Masatoshi Iguchi, Masamichi KobayashiAbstract:Abstract Infra-red and Raman spectra of low-molecular-weight Polyoxymethylene diacetates are investigated and compared with those of the extended- and folded-chain crystals of high-molecular weight trigonal Polyoxymethylene. Some bands assignable to the A2 symmetry species shift towards the high-frequency side, as was found in the folded-chain crystal. The infra-red spectral changes for the extended-chain crystal, folded-chain crystal and low-molecular-weight Polyoxymethylene diacetates that occur on mechanical deformation and melt crystallization are also discussed. A minor shift of Raman bands of the low-molecular-weight Polyoxymethylene diacetates was also found and discussed.
Mu Yan-chun - One of the best experts on this subject based on the ideXlab platform.
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Production,Performance Improvement and Application of Polyoxymethylene
Technology & Development of Chemical Industry, 2012Co-Authors: Mu Yan-chunAbstract:The physical and chemical properties and applications of Polyoxymethylene were briefly introduced.The status quo for modification and research directions of Polyoxymethylene were summarized.The production status,production enterprises and the prospects were brief introduced.And the future development of molyoxymethylene industry was discussed.
