Resumen:
The precipitation of polypropylene (PP) and of high-density polyethylene (HDPE) from decalin solutions, under stirring, yields two polymer-rich phases, one of which is globular and the other is fibrous. Infrared spectra, X-ray diffractograms, optical microscopy and DSC curves showed that the fibrous PP precipitate is richer in stereoregular polymer and yields films more resistant to recrystallization than the globular precipitate. The fibrous HDPE precipitate has a higher methylene/methyl ratio and a higher crystallinity than the globular precipitate. These results are consistent with the predictions of reduced flexibility and stored free-energy formalisms.
