Direct Observation of Morphology and Growth Rate of Extended Chain Single Crystals of Polyethylene

Hikosaka, Masamichi; Seto, Tsuneo

doi:10.1143/jjap.21.l332

Cited by 39 publications

(20 citation statements)

References 2 publications

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“…We showed that at the appropriate high pressure crystallization at low degree of supercooling (Δ T ) of PE gives an isolated ECSC, as suggested by Bassett . We successfully observed the lateral growth rate ( V ) of an isolated ECSC by means of optical microscopy under isobaric conditions by constructing a new high pressure cell …”

Section: Introductionmentioning

confidence: 84%

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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Section: Introductionmentioning

confidence: 84%

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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“…Instrumentation. The pressure cell used in this study is similar to the one designed by Hikosaka and Seto …”

Section: Methodsmentioning

confidence: 99%

“…The pressure cell used in this study is similar to the one designed by Hikosaka and Seto. 12 The maximum attainable pressure in the present setup is 5 kbar, and the temperature could be varied between room temperature and 300 °C. The sample of 0.4 mm thickness is placed between two diamond windows, each of 1 mm thickness and surrounded by Teflon spacer rings.…”

Section: Instrumentationmentioning

confidence: 99%

Chain Mobility in Polymer Systems: On the Borderline between Solid and Melt. 2. Crystal Size Influence in Phase Transition and Sintering of Ultrahigh Molecular Weight Polyethylene via the Mobile Hexagonal Phase

1998

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Polymorphism is a well-established phenomenon in crystalline materials and is important for pharmaceutical and polymeric materials. In our study concerning the processability of polymers, we came across an unusual observation related to polymorphism induced by pressure. The experimental observation is that polyethylene crystals transform from the stable orthorhombic crystal into a transient hexagonal phase. The occurrence of a transient hexagonal phase is shown to be dependent on the polymer crystal size; smaller crystals transform into the transient hexagonal phase at temperatures and pressures much below the thermodynamic critical point Qo, which is located at P = 3.6 kbar and T = 230 degreesC. The crystal size dependence in the phase transition was investigated by in situ X-ray studies in the unirradiated and irradiated solution-crystallized films. Since the chain mobility is rather high in the hexagonal phase, sintering has been attempted via this transient phase using ultrahigh molecular weight polyethylene (UHMW-PE) as a model system. UHMW-PE is an intractable polymer due to its high molar mass but possesses excellent abrasion resistance properties. For this reason it is used as an inlay in demanding applications such as artificial hip and knee joints. The service life of UHMW-PE in these artificial joints, however, is limited due to the poor processing characteristics notably during sintering, and often a second operation is needed to replace the UHMW-PE interface. Sintering via the transient hexagonal phase could provide a solution for this important problem which concerns an increasing number of people.

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“…The intrinsic reason can be ascribed to existence of quite a large amount of amorphous fraction in semicrystalline polymers. To minimize the amorphous fraction and improve the mechanical and thermal properties, preparation of high crystallinity extended-chain crystal (ECC) specimen can be an optimal choice. , However, ECCs are most traditionally achieved under very high pressure condition (e.g., >0.3 GPa), − which is rather rigorous and not easy for general application. Therefore, it is desirable and valuable to develop a mild process to obtain ECCs for common polymers under normal pressure.…”

Section: Introductionmentioning

confidence: 99%

Preparation of Poly(butylene succinate) Crystals with Exceptionally High Melting Point and Crystallinity from Its Inclusion Complex

Ye¹,

Chen²,

Liu³

et al. 2017

Macromolecules

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We successfully developed an effective strategy for preparing poly(butylene succinate) (PBS) material with exceptionally high crystallinity (94.4% from density data) and melting point (∼136 °C) from its urea inclusion complex under normal air pressure for the first time. The strategy consists of three steps: co-electrospinning PBS with urea, thermal treatment, and coalescence of PBS in water. Electrospinning provides well physical mixing between PBS and urea. Thermal treatment causes the assembly of PBS and urea and leads to formation of their inclusion complex, in which PBS chains are separately isolated in urea channels. During the coalescing process the isolated and ordered PBS chains formed crystals with lamellar thickness larger than 26 nmlarger than 5-fold of common PBS crystalafter removing host urea frames. PBS crystals obtained with such high crystallinity and melting point are proved to be the extended-chain crystals (ECCs). Comparative study reveals that the electrospinning and thermal treatment process are necessary in this strategy for preparation of ECC although many other methods can be also used to obtain inclusion complex. Further study shows that the strategy is also feasible for obtaining ECCs of other aliphatic polyesters.

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Direct Observation of Morphology and Growth Rate of Extended Chain Single Crystals of Polyethylene

Cited by 39 publications

References 2 publications

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

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

Chain Mobility in Polymer Systems: On the Borderline between Solid and Melt. 2. Crystal Size Influence in Phase Transition and Sintering of Ultrahigh Molecular Weight Polyethylene via the Mobile Hexagonal Phase

Preparation of Poly(butylene succinate) Crystals with Exceptionally High Melting Point and Crystallinity from Its Inclusion Complex

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