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artículos
Título:
Epoxy-Urethane Copolymers: Relation Morphology -Properties
Autor/es:
P.M. STEFANI; S. M. MOSCHIAR; M. I. ARANGUREN
Revista:
JOURNAL OF APPLIED POLYMER SCIENCE
Referencias:
Año: 2001 vol. 82 p. 2544 - 2552
ISSN:
0021-8995
Resumen:
ABSTRACT: The modification of an amine-cured epoxy resin by the addition of polyurethanes
(PU) was investigated, and their mechanical and impact properties were related
to their microstructure and morphology. For the study, two different PUwere selected:
a commercial sample, D12, with a NCO : OH ratio equal to 2 and end blocked by
reaction with an alkylphenol; and a synthesized sample, with NCO : OH ratio equal to
1 and equally end blocked in our laboratory. The usual trend of improved toughening
and reduced modulus, EF, and compression yield stress, sYC, was observed in all
samples. However, the toughening of the D12-modified samples was larger for the same
initial rubber content. This result correlates with a finer rubber particle separation, but
also the ductilization effect that this rubber has on the epoxy-rich phase. D12 co-reacts
with the epoxyamine, leading to a lower glass transition temperature (Tg) of the
modified system and incomplete phase separation, as observed by scanning electron
microscopy. The practically unreactive PU1 rubber leads to the usual spherical inclusion
morphology observed in modified epoxies, except at 20% rubber content. The
particular morphology generated in this case, co-continuous epoxy-rich and rubber-rich
regions, leads to a material with the largest toughening in this study, but also with an
impressive reduction in mechanical properties.©2001 John Wiley&Sons, Inc. J Appl Polym
Sci 82: 25442552, 2001
Key words: blocked urethane prepolymer; urethaneepoxy copolymers; modified
epoxy; phase separation