Time-dependent measurements polymer crystal nucleation, crystallization

Table 8.1 shows the dependence of K and n on the mechanism of nucleation and growth. Measurements of n have shown that it decreases as crystallization proceeds. Mandelkem [28)] has considered the case of sporadic nucleation on predetermined nuclei that cause a decrease in as crystallization proceeds. However, n may also decrease when A cs is not constant but varies with time. A comparison of degree of crystallinity measurements with spherulitic growth rate measurements on the same polymer [29] shows this. The polymer continues to crystallize after the volume fills with spherulites. The value of n for this secondary crystallization is usually less than for the primary crystallization process. This difference gives rise to a change of n with time. Reference 30 treats this problem theoretically as do Hilliar [31] and Price [32]. 

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