Aging of polymers Flashcards
1
Q
What do amorphous materials below Tg do?
A
They physically age – they are not equilibrium structures
2
Q
What are some techniques used to study aging?
A
- Dilatometry
- Calorimetry
- Creep experiments
3
Q
What is time-temperature superposition?
A
A technique to predict long term mechanical properties of viscoelastic materials from short term experiments
4
Q
What is the stress relaxation modulus dependent on?
A
Temperature and time
5
Q
What does the shift factor (aT) tell you?
A
How much to shift your data along the time axis to account for temperature changes
6
Q
What are some applications of time-temperature superposition?
A
- Predication of viscosity at different temperatures
- Predication of mechanical properties (Youngs modulus, shear modulus)
- Accelerated aging
7
Q
What are some issues with time-temperature superposition?
A
- The WLF parameters C1 and C2 depend slightly on measurement techniques
- WLF equation works better for intrapolation than for extrapolation
