Viscosity Flashcards

1
Q

What’s the Vogel-Eulcher eqn?

A

lnN = A = B/(T - Td)

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2
Q

What happens when T = Td in the Vogel eqn?

A

~ N (viscosity) = infinity, elastic solid

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3
Q

What are the demarcation temperatures?

A
  1. working point: 1E3 (Pa*s), viscosity where glass is easily shaped
  2. softening point: 4E6 (Pa*s), viscosity at which a glass fiber will elongate under its own weight at 1 mm/min
  3. annealing point: 1E12 (Pa*s), viscosity where stresses in the glass can be relieved in 15 in
  4. strain point: 3.2E13 (Pa*s), viscosity at wich stresses in glass can be relieved in 6 hours
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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)

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