Glassy state relaxations

The Metravib Micromecanalyser is an inverted torsional pendulum, but unlike the torsional pendulums described eadier, it can be operated as a forced-vibration instmment. It is fully computerized and automatically determines G, and tan 5 as a function of temperature at low frequencies (10 1 Hz). Stress relaxation and creep measurements are also possible. The temperature range is —170 to 400°C. The Micromecanalyser probably has been used more for the characterization of glasses and metals than for polymers, but has proved useful for determining glassy-state relaxations and microstmctures of polymer blends (285) and latex films (286). 

Chow, T S. Glassy State Relaxation and Deformation in Polymers. Vol. 103, pp. 149-190. 

In the glassy state relaxation times become very large, making the continuation of the polymerization reaction difficult. Moreover, once in the glassy state, small advances in the conversion of functional groups produce a further increase in the already large relaxation times. Thus, the reaction becomes autoretarded and rapidly ceases for practical purposes. Only an increase in the cure temperature can restart the polymerization reaction. 

Different paths of time integration describe different thermal history behavior of the glassy state relaxation and recovery kinetics. Some typical examples of thermal history paths for Eq. (15) were illustrated in Ref. [5J. In this review, we consider mainly that the polymer is cooled from liquid to glass, and is then followed by isothermal annealing. 

By looking at Eqs. (27) and (28), Eq. (32) confirms the customary way of relating P of the stretched exponential function, Eq. (19), to the relaxation time spectrum. The glassy state relaxation is dominated by the part of the spectrum having longer relaxation times. The fractal dynamics of holes are diffusive, and the diffusivity depends strongly on the tenuous structure in fractal lattices, v is the exponent in the power-law relationship between local diffusivity and diffusion length ... 

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