INVESTIGADORES
GALANTE Maria Jose
artículos
Título:
The Structural and Kinetics Factors Governing the Formation of the Gamma Polymorph of Isotactic Polypropylene
Autor/es:
R. ALAMO; M. H.KIM; M.J .GALANTE; J. R ISASI; L. MANDELKERN
Revista:
MACROMOLECULES
Editorial:
AMER CHEMICAL SOC
Referencias:
Lugar: Washington; Año: 1999 vol. 32 p. 4050 - 4062
ISSN:
0024-9297
Resumen:
The molecular, thermodynamic, and kinetic factors that govern the formation and
concentration of the R and ç polymorphs in metallocene-catalyzed isotactic poly(propylenes) have been
studied with a set of polymers that have a wide range in molecular weight and defect contents. With
these polymers it was possible to investigate the influence of molecular weight on ç formation at a fixed
defect concentration, as well as the role of the defect concentration at constant molecular weight. The
major experimental techniques used were wide-angle X-ray scattering and differential scanning
calorimetry complemented by microscopy. From these studies the role of chain microstructure, the
crystallization temperature, and the thermodynamic and kinetic requirement for the formation of the ç
form could be established in more quantitative detail than heretofore. A particular important finding
was the fact that at fixed defect concentration the fractional content of the ç polymorph goes through a
maximum with crystallization temperature. The results that were obtained establish a quantitative
framework within which the underlying bases that lead to formation of the ç form, and its unique
crystalline structure, are discussed.