Effect of Crystallization on Viscosity

The effect of crystallization on the measured viscosity, which is not equal to the true viscosity of the melt, depends upon the details of the crystallization process. If a sample crystallizes via growth of crystals from the surface, the sample is essentially encapsulated in a shell of crystals which prevent deformation, and the viscosity appears to 

The shape of the crystals has some effect on the behavior considered here. Spherical crystals will have less effect on deformation than platelike or needle-like crystals. The minimum volume fraction of crystals which significantly affect the viscosity will thus be a function of the shape and size of the crystals, as well as their composition and location within the sample. Since very little information regarding these effects has been published, details of the effects of crystallization on viscous deformation of melts remain largely a mystery. 

If the relaxation time for viscosity is 1 minute, how long will it take a glass to relax to 95% of its final state  

The viscosity of a glass decreases from 2 x 10 to 1 x lO Pa s if held for a very long time at 550 °C, where the equilibrium viscosity is 10 Pa s. If the viscosity is found to be 1.5 x 10 Pa s after 28 seconds, (a) what is the relaxation time at this temperature and (b) how long will it take for the viscosity to reach 1.2 x 10 Pa s  

If the relaxation time is 47 seconds, how long will it take for a property to relax to 1/3 of the difference between the initial and final states  

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