1995 Fiscal Year Final Research Report Summary
Studies on Control of Higher Oder Structures of Ferrelectric Polymer Crystals and Their Applications
| Project/Area Number |
06452342
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
高分子構造・物性(含繊維)
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| Research Institution | Yamagata University |
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Principal Investigator |
OHIGASHI Hiroji Yamagata University, Faculty of Engineering, Department of Materals Science & Technology, Professor, 工学部, 教授 (90185372)
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| Co-Investigator(Kenkyū-buntansha) |
KOGA Keiko Kyusyu Sangyo University, Faculty of Engineering, Research Associate, 工学部, 助手 (90234723)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Piezoelectric Polymer / Ferroelectric Polymer / Molecular motion / PVDF / High Pressure / Crystallization / Ultrasonic Transducer / Copolymer of VDF |
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| Research Abstract |
This research project was performed for further understanding on dielectric, mechanical, and electromechanical properties of ferroelectric polymers, for development of piezoelectric polymers with high sensuitivity stable at high temperatures by controling micro-structures of ferroelectric polymer crystals, and for applications of newly developed piezoelectric polymer materials. The meterials mainly studied were vinylidene fluoride trifluoroethylene copolymers [P(VDF/TrFE)] and poly (vinylidene fluoride) (PVDF). The followings are the main results :
1. P (VDF/TrFE) single crystaline films comprising fully extended chain crystals having highly preferential orientattion in three principal axs were found to be formed by crystallizing a uniaxilly stretched film in the hexagonal (paraelectric) phase.
2. P (VDF/TrFE)/PMMA blend films composed of fully extended chain crystals were sucessfully obtained by the crystallization in the hexagonal phase of P (VDF/TrFE). Highly crystallized, single-crys
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tal-like films of polyethylene were also found to be formed by crystallization of uniaxially strethe film under high pressure where the hexagonal phase is thermodynamically stable state. The resulting film is optically transparent and includes no lamellar crystal.
3. The elastic, dielectric, and piezoelectric properties of the single crystalline film of P (VDF/TrFE) were studied in a wide temperature range. The film has the highest piezoelectric activities ever found. These measurements and X-ray diffraction study revealed orecise information about the motions of chain molecules in crystal lattices both in ferroelect (R)^<^>c phase and paraelectric phaswe. The paraelectric phase is found to be a liquid crystalline state.
4. High-pressure crystallization of PVDF and P (VDF/TrFE) with high molar content of VDF under the hexagonal phase yielded beta-form extended chain crystals which exhibit strong piezoelectric effects stable up to the melting points (205ﾟC for PVDF).
5. Novel ultrasonic transducers for transverse ultrasonic waves were developed using thiekness shear piezoelectric vibration mode of P (VDF/TrFE). The sensitivity of these transducers were found very high comparable to that of ceramic transducers. Less
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