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Effect of melt annealing on the phase structure and rheological behavior of propylene–ethylene copolymers
Author(s) -
De La Torre Vanesa,
Fris Jorge A. Rodríguez,
Failla Marcelo D.,
Quinzani Lidia M.
Publication year - 2007
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.20775
Subject(s) - materials science , viscoelasticity , rheology , dynamic mechanical analysis , dynamic modulus , polymer , copolymer , annealing (glass) , coalescence (physics) , composite material , ethylene propylene rubber , solvent , ethylene , organic chemistry , chemistry , physics , catalysis , astrobiology
The morphological and rheological properties of a commercial propylene‐ethylene copolymer (PEC) and a series of blends with different concentrations of poly (ethylene‐ co ‐propylene) are investigated. The blends are prepared mixing PEC with fractions obtained from it by solvent extraction. The phase structure of samples exposed to different thermal and mechanical histories was analyzed using scanning electron microscopy. The linear viscoelastic properties of the molten polymers were measured using different test sequences that include dynamic frequency and time sweeps. The phase structure of most blends changes dramatically with time when the polymers are kept in the molten state due to the coalescence of the domains. For example, the initial morphology of PEC which presents domains of ∼1 μm diameter changes to regions of more than 10 μm of average diameter after 90 min at 178°C at rest. Coincidentally, the dynamic moduli of the blends change during annealing reaching values that depend on the mechanical history. For example, the elastic modulus of PEC increases ∼32% during a dynamic time sweep of 45 min using a frequency of 0.1 s −1 , while it decreases ∼18% when a frequency of 1 s −1 is applied. Moreover, the modulus measured at 0.1 s −1 of samples annealed at rest during 45 min is ∼58% larger than that of the fresh material. POLYM. ENG. SCI., 47:912–921, 2007. © 2007 Society of Plastics Engineers