Crystallization in the Quiescent State

Because polymers are only semicrystalline, which means both crystalline and amorphous phases exist, we must define the degree of crystallinity, c. The degree of crystallinity is the volume fraction of crystallinity and is given by 

SPINNING FROM SOLUTION WITHOUT SPECIAL CONDITIONS 

FIGURE 5.18 Morphology of crystaUites in polymers. (Reprinted with permission of the pubhsher 

FIGURE 5.20 Plot of dimensionless linear growth rate of crystallization versus dimensionless temperature. (Reprinted with permission of the publisher from Gandica and Magill, 1972.) 

Free crystallization (i.e., no strain or stress) starts from a number of point nuclei and progresses in all directions at equal linear rates (i.e., the rate of increase of the radius of a spherulite, G, is linear with time). The rate of growth is very dependent on the temperature of crystallization. In particular, G = 0 at 7g and and passes through a maximum at some intermediate temperature, Tk. According to Gandica and Magill (1972) the crystallization process of all the normal polymers follows a master curve. This master curve is a plot of G/Gmax versus a dimensionless temperature, 6  

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A continuous highly oriented fiber can also be produced with the apparatus illustrated in Figure 11 [71]. A solution of ultrahigh molecular weight polyethylene is maintained in the reservoir at a temperature just above that at which it crystallizes in the quiescent state. A stream of this solution is allowed to flow... 

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