Effects of process variables and material properties on melt spinning of pitches have been studied based on simulation using governing equations by Kase and Matsuo. It is shown that the tension
F in a filament depends on spinning conditions as well as viscosity of pitch in the form of
F∝μ
0W1/6ƒ
1(
v0,
vL,
vA)/ƒ
2 (
T0,
Ts,
TA,
E). Here,
W,
v0,
vL and
vA are, mass flow rate, velocity at the spinnerette, winding speed and cross-flow air velocity respectively, and
T0,
Ts and
TA denote temperatures at the spinnerette, at the solidification point and of air. Temperature dependence of viscosity is simplified by an Arrhenius type equation with a pre-exponential factor μ
0 and a flow activation energy
E. To improve spinnability, the maximum tensile stress σ
L should be decreased by increasing
W,
T0 and
TA or by decreasing
vL,
vA,
Ts, μ
0, and
E. In other words, slower cooling of the filament with larger diameter for a pitch with smaller activation energy is preferable to better spinnability. Effects of these factors on diameter, temperature and strain rate of the spinning filament are also discussed.
View full abstract