The polymorphism of poly(vinylidene fluoride). II. The effect of hydrostatic pressure

Doll, W. W.; Lando, J. B.

doi:10.1080/00222346808212450

Cited by 92 publications

(17 citation statements)

References 11 publications

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“…Therefore, the crystal transformation will be induced in PVDF by application of pressure due to changes in the molecular environment, such as interchain distances. Actually, Doll and Lando (1968) reported that the highpressure crystallized sample has a crystal form different from the Form I1 structure, which is obtained by melt-crystallization at atmospheric pressure. On the other hand, direct observation of the crystal transformation process at high pressures and detailed structural analysis on the PVDF samples heat-treated under high pressure were performed by the present author and his group (Matsushige, Nagata and Takemura, 1978; Matsushige, Nagata, Imada and Takemura, 1980).…”

Section: Phase Transformation During Heatingmentioning

confidence: 98%

Pressure effect on phase transition in ferroelectic polymers

Matsushige

1989

Phase Transitions

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Pressure effects of phase transition behaviour in two kinds of ferroelectric polymers of poly(viny1idene fluoride), PVDF, and copolymers of vinylidene fluoride and trifluoroethylene, (VDFFrFE), are discussed.In the case of PVDF, several high-pressure treatments including a high-pressure annealing and a uniaxial compression were shown to induce a crystal transformation from a non-polar Form I1 crystal to a polar Form I crystal, which has ferroelectric characteristics and high piezoelectric activity. In addition, substantial pressure effects on ferroelectric phase transition points as well as crystal structures were observed for (VDFDrFE) copolymers with different VDF contents. The most significant pressure effects were observed for copolymer samples with unstable ferroelectric structures at atmospheric pressure. From high-pressure X-ray and Raman scattering studies, these pressure effects were suggested to originate from the pressure-induced conformational transition from gauche to trans in the molecular chains.

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Section: Phase Transformation During Heatingmentioning

confidence: 98%

Pressure effect on phase transition in ferroelectic polymers

Matsushige

1989

Phase Transitions

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“…N o observable long-period spacings have been obtained from small-angle photographs for the low-pressure-crystallized o r the high-pressure crystallized PVF,. However, electron microscopy of fracture surfaces of high-pressure crystallized PVF, revealed step heights on the order of 680 A [3].…”

Section: Resultsmentioning

confidence: 98%

“…With this experimental arrangement, samples crystallized at high p r e s s u r e could be drawn t o a ratio of 2.5 to 1. Figure 1 depicts the Debye-Scherrer powder photographs for the three polymorphic phases of PVF, as originally presented by Doll and Lando [3]. As can be seen in Fig.…”

Section: Methodsmentioning

confidence: 98%

“…The samples were pressure-crystallized in a highp r e s s u r e dilatometer which has been previously described [3,4]. In a previous paper [3], the effect of p r e s s u r e on the melting behavior of PVF, has been discussed. By knowing the melting point under a given hydrostatic pressure, it was possible to determine the degree of supercooling of a sample.…”

Section: Methodsmentioning

confidence: 99%

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The polymorphism of poly(vinylidene fluoride) IV. The structure of high-pressure-crystallized poly(vinylidene fluoride)

Doll

Lando

1970

Journal of Macromolecular Science, Part B

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A detailed study of high-pressure-crystallized poly(viny1idene fluoride) has indicated that a mixture of low-melting phase II and high-melting phase I is present, rather than a new crystalline phase (phase 111) as originally suggested.The relative amounts of phase I and phase I1 resulting from crystallization under pressure a r e a function of pressure and the degree of supercooling. Pressure crystallization at 285°C and 5500 atm results in samples which were pure phase I with an increased melting point of 187°C.

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“…Other forms can be produced by the application of electrical fields. 5,6 Some studies on the development of structure in PVDF fibers and tapes during melt spinning and deformation have been conducted using simultaneous synchrotron radiation as well as X-ray from laboratory generators for wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). [7][8][9][10] Cakmak and co-workers 7 have shown that the appearance of the b-phase is stress dependent, first occurring at a spinline stress of 3 MPa and increasing in concentration as stress is increased.…”

Section: Introductionmentioning

confidence: 99%

Development of a fiber structure in poly(vinylidene fluoride) by a CO2 laser-heated drawing process

Kang

Kim

Ikehata

et al. 2010

Polym J

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Rapid and uniform heating by CO 2 laser radiation can fix the position where necking occurs. Therefore, this study investigated the development of a fiber structure in poly(vinylidene fluoride) in continuous drawing by in situ measurement using synchrotron X-ray radiation with a time resolution of several hundred microseconds. Two neck-deformation behaviors were observed in the laser drawing: a moderate neck deformation under low drawing stress and a steep neck deformation under high drawing stress. The low drawing stress resulted in a mixture of a-and b-crystals in which the b-crystal was formed within 1 ms after the necking, earlier than the a-crystal. The development of the fiber structure under high drawing stress was almost complete in less than 1 ms, and the developed structure contained only b-crystals. Small-angle X-ray scattering images showed meridional streaks at low drawing stress, whereas a four-pointed pattern occurred under high drawing stress. Low drawing stress generated a long periodic structure that was defective in the periodic regularity of crystalline and amorphous regions, although the molecular chains were nearly oriented along the fiber axis. The high drawing stress resulted in a well-packed structure of adjacent fibrils with alternating amorphous and crystalline regions.

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The polymorphism of poly(vinylidene fluoride). II. The effect of hydrostatic pressure

Cited by 92 publications

References 11 publications

Pressure effect on phase transition in ferroelectic polymers

Pressure effect on phase transition in ferroelectic polymers

The polymorphism of poly(vinylidene fluoride) IV. The structure of high-pressure-crystallized poly(vinylidene fluoride)

Development of a fiber structure in poly(vinylidene fluoride) by a CO2 laser-heated drawing process

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