Melting-recrystallization thickening

Tc, is increased the temperature of peak L is found to increase in direct proportion while that of peak H increases only slightly. As Tc is further increased, the L endotherm Increases in size while the H endotherm diminishes and eventually disappears. These trends generally confirm those reported previously (2 ). and suggest that the multiple peaks are most likely the result of lamellar thickening processes, perhaps requiring melting and recrystallization (23). 

In the following figures, further experiments are linked to the annealing and recrystallization of a number of additional polymers. In Fig. 6.81 the increase of lamellar thickness is illustrated on the example of solution-grown polyethylene. The crystals were collected in dried mats. The graph on the right side allows a comparison with data on melt-crystallized and annealed polyethylene (see also Sect. 5.2). Sufficiently mobile and flexible molecules, such as polyethylene, can thicken by chain... 

The extent to which the thickening process occurs by solid-state reorganization of the parent crystals or by melting and recrystallization into thicker crystals is stiU a matter of discussion and probably depends on the poly-... 

In one case, each of the multiple melting peaks can be attributed to the various crystalline substructures, such as unit cells, lamellae, or spherulites, present in the polymer. In the alternative interpretation, multiple melting was attributed to the melting of thinner lameUae/crystals, recrystallization to thicker ones, and remelting of the thickened lamellae during DSC scanning. 

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