Crystallization from a single-phase mixture

A miscible blend of amorphous and crystalline polymers usually means a single phase in the melt and a neat crystalline phase with a mixed amorphous region in the sohd. Because of chain folding during crystallization, the crystal lamellae are formed. Their radical growth usually lead to the formation of spheniUtes [Nadkami and Jog, 1991]. 

It was shown that amorphous polymers certainly reside between crystal lamellae as a single phase mixture in poly(8-caprolactone) (PCL)/poly(vinyl chloride) (PVC) blends [Stein, 1978]. When the content of the amorphous polymer is high, its excess is excluded from interlamellar region to the outside of lamellar stacks in poly(etheretherketone)/ poly(etherimide) blends [Lee et ah, 1997]. 

Another type of morphology development was reported for PP/EPR blends [Inaba et al., 1986]. High molecular weight blends of PP and EPR are immiscible. One-phase blends were prepared by precipitation from a solution. This mixture underwent phase separation via spinodal decomposition (SD), followed by crystallization. However, in this case the spherulites were formed seemingly ignoring the bi-continuous SD-structure. 

Additional interesting information was reported for PCL/SAN blends [Schulze et al.] and PCL/ oligomeric-PS blend [Tanaka et al., 1985 Li and Jungnickel, 1993 Nojima et a/., 1991]. 

It is well-known that the rate of crystallization of a crystalline polymer is often reduced by blending with a miscible amorphous polymer. Some typical examples are blends of PVDF/PMMA [Tanaka et al., 1985], PVDF/PEA [Alfonso and Russel, 1986], PEO/PMMA [Briber and lOioury, 1987] and PCL/SAN (19.2 wt% acrylonitrile) [ICressler et al., 1991]. 

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