A novel approach to study self-nucleation in semicrystalline polymers is presented. Self-nucleation, i.e., the peculiar increase of recrystallization kinetics associated with a range of melting temperatures above or below the melting point, is investigated in parallel with differential scanning calorimetry (DSC) and rheological measurements, for a series of metallocene propene/ethylene random copolymers of varying comonomer content. DSC experiments revealed the exact temperature region where self-nucleation effects are detected in the various samples, while with dynamic viscoelastic results the obedience to the time-temperature superposition principle (TTS) is tested, for both self-nucleated and homogeneous melts. Self-nucleated melts do not obey to the TTS principle, contrary to fully isotropic copolymer melts. Such rheological thermocomplexity constitutes the first physical experimental evidence of the presence of melt heterogeneities, which act as self-nuclei when the melt is cooled and recrystallizes. The degree of thermorheological complexity of the different copolymers is quantified and correlated with the original crystalline content of the copolymer.

Thermorheologically complex self-seeded melts of propylene-ethylene copolymers

CAVALLO, DARIO;
2017-01-01

Abstract

A novel approach to study self-nucleation in semicrystalline polymers is presented. Self-nucleation, i.e., the peculiar increase of recrystallization kinetics associated with a range of melting temperatures above or below the melting point, is investigated in parallel with differential scanning calorimetry (DSC) and rheological measurements, for a series of metallocene propene/ethylene random copolymers of varying comonomer content. DSC experiments revealed the exact temperature region where self-nucleation effects are detected in the various samples, while with dynamic viscoelastic results the obedience to the time-temperature superposition principle (TTS) is tested, for both self-nucleated and homogeneous melts. Self-nucleated melts do not obey to the TTS principle, contrary to fully isotropic copolymer melts. Such rheological thermocomplexity constitutes the first physical experimental evidence of the presence of melt heterogeneities, which act as self-nuclei when the melt is cooled and recrystallizes. The degree of thermorheological complexity of the different copolymers is quantified and correlated with the original crystalline content of the copolymer.
File in questo prodotto:
File Dimensione Formato  
Sangroniz_Rheology_self_nucl_propeth_copo_Macromolecules_2017.pdf

accesso chiuso

Tipologia: Documento in versione editoriale
Dimensione 1.5 MB
Formato Adobe PDF
1.5 MB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11567/863089
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 50
  • ???jsp.display-item.citation.isi??? 49
social impact