Viscosity Flashcards
1
Q
What’s the Vogel-Eulcher eqn?
A
lnN = A = B/(T - Td)
2
Q
What happens when T = Td in the Vogel eqn?
A
~ N (viscosity) = infinity, elastic solid
3
Q
What are the demarcation temperatures?
A
- working point: 1E3 (Pa*s), viscosity where glass is easily shaped
- softening point: 4E6 (Pa*s), viscosity at which a glass fiber will elongate under its own weight at 1 mm/min
- annealing point: 1E12 (Pa*s), viscosity where stresses in the glass can be relieved in 15 in
- strain point: 3.2E13 (Pa*s), viscosity at wich stresses in glass can be relieved in 6 hours
4
Q
What are long and short glasses?
A
~ long: broad temp range w/ which the glass can be worked (lead silicate)
~ short: solidifies quickly, good for high-speed automated manufacturing (e-glass)