Resonant frequency mode, dynamic mechanical

Test pieces 25 x 12 x 3 mm were subjected to dynamic mechanical analysis in a Du Pont 983 instrument, operating in resonant frequency mode. Samples were heated from -150 to 150°C at 20 C min. The oscillation displacement amplitude used was 0.05 mm. Data was processed using TA 2100 software. 

In the hydrate lattice structure, the water molecules are largely restricted from translation or rotation, but they do vibrate anharmonically about a fixed position. This anharmonicity provides a mechanism for the scattering of phonons (which normally transmit energy) providing a lower thermal conductivity. Tse et al. (1983, 1984) and Tse and Klein (1987) used molecular dynamics to show that frequencies of the guest molecule translational and rotational energies are similar to those of the low-frequency lattice (acoustic) modes. Tse and White (1988) indicate that a resonant coupling explains the low thermal conductivity. 

On the other hand certain elastic protein-based polymers can exhibit good elastic moduli and yet contain dynamic structural regularities that exhibit mechanical modes. In fact elastic protein-based polymers can be designed to exhibit mechanical resonances with high loss factors over interesting frequency ranges. 

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