State diagram and the glass transition - The glass transition - Viscosity and temperature dependence of the glass transition
3 important questions on State diagram and the glass transition - The glass transition - Viscosity and temperature dependence of the glass transition
The rate of the jumping process of water molecules depends on two things
- The amount of motion of the molecules
- The number of holes that happen to be present
What is the effect of the reduction of temperature on the viscosity of a solution?
- Number of sufficiently energetic jumps is reduced --> The molecules have less thermal (Brownian) motion, so that means jumps will be less frequent
- The amount of space to accommodate molecules that have jumped, has become less --> The lower amount of thermal motion will also mean that the molecules will move closer together, there is simply less space needed to accommodate all the motion. Therefore, the density will increase and the molar volume will decrease. Since the molecules themselves will not occupy any less space, this means that the free volume is reduced.
Which equations for temperatures that are not too far away/far away from the glass transition temperature?
Not too far away --> WLF
Far away (thin viscous liquids, such as water or ethanol), below 30% w/w in sugar solutions --> Arrhenius
Far away (thin viscous liquids, such as water or ethanol), below 30% w/w in sugar solutions --> Arrhenius
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