Flow-induced crystallization induction time

In general, the induction time for flow-induced crystallization is shorter [47] and the crystallization rate itself is faster [48], as illustrated in Figure 15.1 in Chapter 15. 

The effect of Talc and Montmorillonite (Closite Na+) on the crystallization kinetics of PLA was investigated. The lowest crystallization induction period and maximum crystallization speeds were observed at around 100°C. At this temperature the crystallization half-time of PLA was decreased from a few hours to 8 minutes by addition of 1% Talc. Further addition of Talc did not result in significant half-time reduction. The Montmorillonite Closite Na-i- was shown to be less effective than Talc as a nucleating agent and could not decrease the half-life below 30 min. Flow induced crystallization was observed... 

Well known examples of orientation induced crystallization are the stretching of rubber, fiber orientation in polyamides and polyesters, and the biaxial stretching of polycarbonate filuK. An example of thermal effects during induct crystallization in rubber is shown in Fig. 45, where the heat flow (Q) for successive steps of elongation and retraction is plotted as a function of time. 

Generally speaking, excitation of a medium by short laser pulses can be used to study dynamic properties of the medium over a very wide time range. Here, we have shown that nanosecond-pulse excitation can yield information about the dynamics of molecular reorientation on the -10-sec time scale, and thermal effect on the 10—l(X)-msec time scale. The power of this technique lies in the fact that a single 6-function-like laser pulse may induce a number of fundamental excitation modes of vastly different time constants. Consider, for example, molecular reorientation coupled with flow induct by a picosecond laser pulse in a liquid crystal. It can be shown that, aside from the thermal effect, the transient behavior will manifest itself with three characteristic time constants ... 

---

See also in sourсe #XX -- [ ]

---