What is free volume theory?
The free-volume theory extends the above ideas and also allows a quantitative assessment of the plasticization process. The free volume is a measure of the internal space available within a polymer matrix. When the free volume increases, so does the freedom of movement of polymer chains.
How do you calculate free volume?
Free volume is the space present inside the polymer, and it can be measured by positron annihilation method. Free volume changes as the molecules oscillate. If the intermolecular cohesion increases the free volume decreases.
What is TG in volume?
The transition point is the glass transition. The glass transition is sensitive to the rate of cooling as show in the second figure below. From L. H. The extrapolated differences in volume between a glass and the extrapolation of the melt curve is called the free volume.
What is a shift factor?
A shift factor to a particular line is the effect of this injection and withdrawal on the flow on the line. That is, the shift factor is the ratio of the change in the flow on a line to a change in the injection and a corresponding change in the withdrawal.
Who won WLF vs scars?
The invasion ultimately goes sour, as Abby later hears a radio message confirming that the Scars won the upper hand and there were hundreds of casualties on the WLF side, leaving the group weaker than ever at the end of the game. Interestingly, however, the invasion also reveals peculiar details about WLF’s biases.
Did the WLF lose?
In retaliation, the WLF unleashed the military’s weapons on the Seraphites, reigniting the war. It was their first significant defeat in the war and caused many to question their loyalty to the group.
How is the WLF shift factor related to viscosity?
Williams, Landel and Ferry (1955) have suggested that the viscosity η at a temperature T may be related to the viscosity ηg at the glass transition temperature: 2 where aT is the so called WLF shift factor. Using the universal values of fg and αf yields two new constants: The two constants are not universal at all.
Is the WLF equation applicable to temperatures above T G?
However, when the constants are obtained with data at temperatures above the glass transition temperature (T g ), the WLF equation is applicable to temperatures at or above T g only; the constants are positive and represent Arrhenius behavior. Extrapolation to temperatures below T g is erroneous.
How is the viscosity of air related to temperature?
The value of the dynamic viscosity coefficient is found to be a constant with pressure but the value depends on the temperature of the gas. For air, D. M. Sutherland provides an equation for the dependence on temperature T: where mu0 and T0 are reference values given at sea level stanfard conditions.
What is the empirical equation for the WLF equation?
The empirical WLF equation describing shift factor, a T, is: where ε 0=strain at reference temperature, T 0 =reference temperature, t=time, ε=strain at an arbitrary temperature, T=arbitrary temperature and a T =shift factor. For amorphous polymers, the WLF equation applies to temperature range varying from Tg to about T g +100°C.