X-Ray Studies of Polyethylene under High Pressure

Yasuniwa, Munehisa; Enoshita, Ryosuke; Takemura, Tetuo

doi:10.1143/jjap.15.1421

Cited by 94 publications

(38 citation statements)

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“…For HDPE, the sharp scattering maxima, centered at q ~ 15 and 16.7 nm -1 in the WAXS spectra, are associated with the (110) and (200) planes of the orthorhombic unit cell. [54][55][56][57][58] The corresponding scattering maxima observed for HP3 and P3 are centered at lower q values, which indicates an increased lattice constant and, as expected, a lower degree of crystallinity. In the case of P3, only the first scattering peak is evident.…”

Section: Figuresupporting

confidence: 62%

Synthesis of poly(sulfonate ester)s by ADMET polymerization

et al. 2014

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Many hydrocarbon polymers containing heteroatom defects in the main chain have been investigated as degradable polyethylene-like materials, including aliphatic polyesters. Here, acyclic diene metathesis (ADMET) polymerization was used for the synthesis of aliphatic poly(sulfonate ester)s. The requisite sulfonate ester containing α,ω-diene monomers with varying numbers of methylene groups were synthesized, and their polymerization in the presence of ruthenium-N-heterocyclic (Ru-NHC) alkylidene catalysts was studied. A clear negative neighboring group effect (NNGE) was observed for shorter dienes , either inhibiting polymerization or resulting in low-molecular-weight oligomers. The effect was absent when undec-10-en-1-yl undec-10-ene-1-sulfonate was employed as the monomer, and its ADMET polymerization afforded polymers with appreciable number-average molecular weights of up to 37,000 g/mol and a dispersity Đ of 1.8. These polymers were hydrogenated to afford the desired polyethylene-like systems. The thermal and morphological properties of both saturated and unsaturated polymers were investigated. The incorporation of sulfonate ester groups in the polymer backbone offers an interesting alternative to other heteroatoms and helps further the understanding of the effects of these defects on the overall polymer properties.

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Section: Figuresupporting

confidence: 62%

Synthesis of poly(sulfonate ester)s by ADMET polymerization

et al. 2014

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“…As to the origin of ECCs of polyethylene (PE), Uhlmann 9 and Takemura et al 10 maintained that ECCs are formed directly from the melt, while Wunderlich et al 11 and Bassett et al 12 insisted that ECCs are formed from FCCs through lamellar thickening. Note that they studied a stacked lamellar system, i.e., the secondary crystallization process.…”

Section: Introductionmentioning

confidence: 99%

Lamellar Thickening Growth of an Extended Chain Single Crystal of Polyethylene. 1. Pointers to a New Crystallization Mechanism of Polymers

et al. 1997

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Crystallization and growth of an isolated extended chain single crystal (ECSC) of polyethylene (PE) under high pressure from the melt into the mobile phase, such as hexagonal phase, was studied by in-situ optical microscopy and transmission electron microscopy. Direct evidence is obtained that an isolated ECSC was formed from a folded chain single crystal through the combination of newly recognized "lamellar thickening growth" and the long familiar lateral growth. This confirmed the prediction of chain sliding diffusion theory that the lamellar thickening growth takes place the important role in the origin of folded chain and extended chain crystals (FCCs and ECCs) presented by one of authors (M.H.) previously. The lamellar thickness (l) inceased linearly with time (t), indicating that the lamellar thickening growth rate is constant as long as the crystal is in isolation, i.e., it does not impinge on others, directly reflected also by the straightened taper of the cross-sectional shape. This is quite different from the well-known lamellar thickening of stacked-lamellar system where l increases linearly with logarithm of time (log t). It is shown that the difference is due to the difference between the primary and the secondary crystallization processes. The lamellar thickening growth rate (U), defined by (dl/dt)/2, was measured for the first time by developing two methods, "direct method" and "mapping method".

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“…Then the precise temperature change of lattice parameters in orthorhombic phase and HPP were obtained. 9 Takemura et a/. 10 · 11 studied the physical properties of HPP by various experimental methods and characterized HPP to be like a liquid crystal.…”

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confidence: 99%

“…These changes of the lattice parameters are similar to those in the case of the transition from the orthorhombic phase to HPP in a bulk sample under high pressure. 9 From this fact, it is suggested that both ortho.-hexa. transition in the constrained UDPF and transition to HPP in the bulk sample occur with the same structural change.…”

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Hexagonal Phase of Polyethylene Fibers under High Pressure

Tsubakihara

Nakamura

Yasuniwa

1991

Polym J

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ABSTRACT:The hexagonal phase of a constrained ultra-drawn polyethylene (PE) fiber (UDPF) was studied in detail. The melting process of the constrained UDPF was examined at atmospheric pressure by DSC and X-ray measurement. The hexagonal phase appears prior to melting in the constrained UDPF. The phase diagram showing the pressure change of the hexagonal phase was determined by high pressure DT A up to about 600 MPa. The temperature range of the hexagonal phase increases with pressure and coincides with that of so-called "high pressure phase" (HPP) of it above about 300 MPa. That is, the hexagonal phase of the constrained UDPF is the same as HPP. The phase diagrams of three kinds of PE samples, two constrained UDPFs and a bulk sample composed of extended-chain crystals, determined by high pressure DT A, were compared with one another. The constraining force applied to these PE samples considerably raises the melting temperature of HPP, while it has almost no effect on the transition temperature from orthorhombic phase to HPP. By constraining force, HPP of UDPF appears even in the low pressure region that includes atmospheric pressure.

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X-Ray Studies of Polyethylene under High Pressure

Cited by 94 publications

References 0 publications

Synthesis of poly(sulfonate ester)s by ADMET polymerization

Synthesis of poly(sulfonate ester)s by ADMET polymerization

Lamellar Thickening Growth of an Extended Chain Single Crystal of Polyethylene. 1. Pointers to a New Crystallization Mechanism of Polymers

Hexagonal Phase of Polyethylene Fibers under High Pressure

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