1993 Fiscal Year Final Research Report Summary
Analysis for Phase Transitions and Critical Phenomena in Even-Even Nylon Crystals
| Project/Area Number |
04452041
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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 |
固体物性
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| Research Institution | Kyoto Institute of Technology |
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Principal Investigator |
ITOH Takashi Kyoto Inst. Tech. Polym. Sci. & Tech. associate Professor, 繊維学部, 助教授 (60107159)
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| Co-Investigator(Kenkyū-buntansha) |
KONISHI Takashi Kyoto Inst. Tech. Polym. Sci. & Tech. Professor, 繊維学部, 教授 (70027861)
KONISHI Takashi Kyoto Inst. Tech. Polym. Sci. & Tech. Professor (70027861)
KONISHI Takashi Kyoto Inst. Tech. Polym. Sci. & Tech. Professor (70027861)
KONISHI Takashi Kyoto Inst. Tech. Polym. Sci. & Tech. Professor (70027861)
KONISHI Takashi Kyoto Inst. Tech. Polym. Sci. & Tech. Professor (70027861)
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| Project Period (FY) |
1992 – 1993
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| Keywords | Nylon 66 Single Crystal / First-Order Phase Transition / Second-Order Phase Transition / Critical Phenomena / Mean-Field Approximation / Specific Heat Anomaly |
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| Research Abstract |
Fifty years have passed since Brill discovered the characteristic change in the crystal structure of nylon 66 at elevated temperatures. Nevertheless, there are still serious unanswered questions about the temperature dependence of the crystal structure and associated molecular motion of the polyamide.
Electron diffraction patterns and specific heat at constant pressure (C_p) are recorded in a temperature range between approximately 300 K and 500 K for a nylon 66 crystal precipitated at 418 K from 0.05-wt% 1,4-butanediol solution. The C_p is found to take a maximum value at 468 K (T_t) under 0.1 MPa (atmospheric pressure). Three reflections of 100, 010 and 110 can be observed independently in an electron diffraction pattern, all of which show symmetrical single-peak profiles at temperatures lower than T_t, while 010 and 110 profiles are found to be asymmetric or to have shoulders in the smaller-diffraction-angle region at T_t. These results give the first evidence that two crystalline ph
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ases coexist or that first-order phase transition occurs at T_t in the nylon 66 crystal.
X-ray diffraction patterns from nylon 66 crystal precipitated at 418 K from the 0.5 wt% solution are obtained at elevated temperatures and pressures. High- and Low-tem-perature phases are confirmed to coexist at transition temperature under pressures higher than 100 MPa, while the structural change is continuous at 0.1 MPa. It gives the first evidence for homopolymer crystals that second-order phase transition occurs in nylon 66 crystal betreen 0.1 and 100 MPa. Devergence of the isothermal compressibility (K_T) near 0 Pa suggests that the critical point may exist around atmospheric pressure.
Theoretical and experimental comparisons are performed between nylon 66 and 46, the latter of which does not show any specific heat anomaly. It shows that differences in the intra- and intermol-ecular interaction energies between nylon 66 and nylon 46 play an important role in causing such themodynamical behaviors of even-even polyamide crystals. Less
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