| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2000: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1999: ¥2,200,000 (Direct Cost: ¥2,200,000)
|
|---|
| Research Abstract |
Dielectric spectroscopy is widely used to study molecular dynamics in dispersed systems. With increasing frequency, the dielectric constant, ε', often decreases, and the dielectric loss, ε", shows a peak due to the delay in dipole moments, this phenomenon being the so-called dielectric relaxation. In this study, the glass transition of gelatin was analyzed by dielectric relaxation.
The dielectric properties of gelatin in the glassy state were measured from 100Hz to 1MHz over a temperature range of -20℃〜60℃. Samples with different water content were prepared by varying the drying time for gelatin solution ; the glass transition temperature, T_g, was determined by DSC.The maximum of ε" , i.e. the dielectric relaxation was observed for glassy gelatin ; the relaxation time τwas evaluated from the peak of ε". The activation energy E_<ax>obtained from an Arrhenius plot of τdecreased with increasing water content Based on the order of magnitude of E, the dielectric relaxation observed was considered be β relaxation reflecting the local motion of molecules. τand E, are considered to be suitable parameters for the characterization of the plasticizing effect of water on a glassy material
On the other hand, in the low frequencies and at temperatures around or above T_g, the electrical properties of materials containing electrolytes and/or water, the peak of ε"was masked due to large dc conductivity. For analyzing such systems, ε"and ε"were transformed into M^* formalism (M^*=1/(ε'-iε") =M'+iM", i, the imaginary unit) the peak of M", e.g., the relaxation was observed and the relaxation time, τ_N was evaluated from the peak of M". The value of the activation energy, E_τ was evaluated from an Arrhenius plot of 1/τ_N, . The value of E_τ in the glassy state was larger than that in the rubbery state.
|
