Dynamic Mechanical Properties of Polyoxymethylene I

Miki, Kyosuke; Yokokawa, Yukimoto; Hikichi, Kunio; Furuichi, Jiro

doi:10.1143/jjap.5.818

Cited by 10 publications

(3 citation statements)

References 10 publications

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“…23 The intensity of the mechanical a relaxation of melt-crystallized polyoxymethylene also increases with increasing thickness of lamella. 24 This relationship is in qualitative agreement with the requirements of Okano's theory. However the relaxation intensity was found to increase by gamma-ray irradiation on the melt-crystallized polyoxymethylene without increasing the lamella thickness.…”

Section: To~7o°csupporting

confidence: 79%

Dynamic Mechanical Properties of Polyoxymethylene, IV

Miki

1970

Polym J

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Dynamic mechanical measurements are made with a torsion pendulum apparatus over about three decades of frequency in the a relaxation region of the single crystals of polyoxymethylene. Real and imaginary parts of complex rigidity are measured in each of the three specimens, that is, a mat of single crystals prepared by gradual cooling; a rod of isothermally crystallized single crystals and a heat-treated sample of the single crystal mat. The composite relaxation curves are made by superposing the dispersion curves of real and imaginary parts of complex rigidity on each of the specimens. The composite relaxation curve of loss tangent is also made by superposing the loss tangent curves for the single crystal mat. The activation energies of the a relaxation evaluated from the temperature dependence of the horizontal shift factor are 37 kcal/mol (T < 40°C), 25 kcal/mol (40°C < T < 90°C) and 38 kcal/mol (T > 90°C) respectively. The magnitude of vertical shift along the logarithmic rigidity axis is independent of temperature above about 100°C and 115°C for the single crystal mat and the piled rod of the single crystals, but the magnitude varies linearly with increasing temperature above about 50°C for the heat-treated sample of the mat.

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Section: To~7o°csupporting

confidence: 79%

Dynamic Mechanical Properties of Polyoxymethylene, IV

Miki

1970

Polym J

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“…13 It was shown that the r-ray irradiation degrades the covalent bond of main chains. Miki, eta/., 14 have found from dynamic mechanical measurements that the real part of complex rigidity decreases with increasing irradiation dosages. They expected lattice defects to have been produced by irradiation in the crystalline region.…”

Section: Discussionmentioning

confidence: 99%

X-Ray Determination of the Disorder in Poly(oxymethylene) Crystals

Aoki

Chiba

Kaneko

1971

Polym J

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S:Ruland's concept of the isotropic disorder function is used to estimate the disorder parameter and degree of crystallinity in r-ray irradiated and solution-grown poly(oxymethylene)s. The degree of crystallinity increases with increasing irradiation dosage, but the disorder parameter remains constant. The disorder is attributed to thermal motions, the root mean squared amplitude being about 0.2 A at room temperature. The increase in crystallinity is mainly caused by degraded molecular chains in the disordered region. The disorder parameter of the solution-grown crystal is larger than that of r-ray irradiated samples and decreases with annealing. Increase in the disorder parameter in the solution-grown crystal may be caused by the lattice imperfections in the crystal. In both samples the degree of crystallinity decreases above 70°C, and at 120°C it is 5% less than the value at room temperature. In this temperature range, partial melting at the surface layer of the crystal may take place.KEY WORDS X-Ray I Crystallinity I Lattice Disorder I Thermal Motion I Irradiation I Solution-Grown Crystal 1 Annealing I Partial Melting I Poly(oxymethylene) I Ruland 1 ' 2 has developed an X-ray method of crystallinity determination which takes into account the diffuse scattering due to thermal motions and lattice imperfections in a crystal. Using his method, the degree of crystallinity and the disorder parameter in polyethylene/· 3 • 4 polypropylene, 1 and other crystalline polymers 2 • 5 • 6 have been measured. It has been found that the disorder parameter is predominantly determined by the thermal motions in linear polymers in which the interchain attraction is due to van der Waals force only. 1 The influences of crystallization conditions and the effect of r-ray irradiation on the disorder in a crystal and on the degree of crystallinity are investigated. The disorder parameter and degree of crystallinity vary with the r-ray irradiation, crystallization conditions and the annealing. The temperature dependence on the disorder parameter and on the degree of crystallinity is also shown. The mechanism of those variations is discussed in terms of thermal motions and lattice imperfections.Recently, Davis, et al.,7 reported that a unit ·cell dimension of polyethylene is not unique but varies systematically with crystallization ·conditions, annealing and deformation. It is interesting to investigate whether the disorder parameter also varies with such treatment.In the present study, r-ray irradiated and solution-grown poly(oxymethylene)s (POM) were used. It would be useful to measure the disorder parameter of the solution-grown crystal, since the disorder parameter has not previously been discussed in respect of samples crystallized from solution. x., =K"-"-0 ----

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“…Most of the corresponding experiments were performed in the 1960s by mechanical and dielectric measurements, resulting in a wide range of reported activation energies from E a =88 kJ/mol to 328 kJ/mol [22][23][24][25][26][27] . Schmidt-Rohr and Spiess reported the first NMR-based value of E a = (83 ± 8) kJ/mol for a not further specified POM-homopolymer 28 .…”

Section: Characteristic Timescalesmentioning

confidence: 99%

Lamellar thickness in semicrystalline polymers as a result of the competition between crystal growth and intracrystalline chain dynamics

Schulz¹,

Schäfer²,

Saalwächter³

et al. 2021

Preprint

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The non-equilibrium thickness of lamellar crystals in semicrystalline polymers varies largely between different polymer systems and depends on the crystallization temperature Tc. There is currently no consensus on the mechanism of thickness selection. Previous work has highlighted the decisive role of intracrystalline chain dynamics (ICD) in special cases, but a systematic dependence of lamellar thickness on relevant timescales such as that of ICD and stem attachment has not yet been established. Studying the morphology by small-angle X-ray scattering and the two timescales by NMR methods and polarization microscopy, we here present data on poly(oxymethylene), a case with comparably slow ICD. It fills the gap between previously studied cases of absent and fast ICD, enabling us to establish for the first time a quantitative dependence of lamellar thickness on the competition between the noted timescales.

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Dynamic Mechanical Properties of Polyoxymethylene I

Cited by 10 publications

References 10 publications

Dynamic Mechanical Properties of Polyoxymethylene, IV

Dynamic Mechanical Properties of Polyoxymethylene, IV

X-Ray Determination of the Disorder in Poly(oxymethylene) Crystals

Lamellar thickness in semicrystalline polymers as a result of the competition between crystal growth and intracrystalline chain dynamics

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