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artículos
Título:
Rubber Modified Vinyl ester resins of different molecular weights
Autor/es:
M. L. AUAD; M. PROIA; J. BORRAJO; M.I. ARANGUREN
Revista:
JOURNAL OF MATERIALS SCIENCE
Referencias:
Año: 2002 vol. 37 p. 4117 - 4126
ISSN:
0022-2461
Resumen:
The morphology, as well as the related fracture and mechanical behavior of vinyl ester
resins (DVER) of different molecular weights cured with styrene (S) and modified with two
different liquid rubbers are presented and discussed. The liquid rubbers are: carboxyl
terminated poly(butadiene-co-acrylonitrile) (CTBN), a common toughening agent for epoxy
resins, and an almost unreactive rubber with the DVER and S comonomers, and a reactive
rubber (vinyl terminated poly(butadiene-co-acrylonitrile), (VTBN). The initial miscibility of
the modified systems and the reactivity of the rubber determine the final morphology of
the material. This morphology will correspond to a continuous main phase (rich in the
DVER-S copolymer) with simple rubber rich inclusions (as in the epoxy-rubber systems) or
with inclusions with a complex internal structure, where phase separation occurs as in the
low profile modified unsaturated polyester resins. The morphologies developed are
strongly dependent on the resin molecular weight as well as on the elastomer added. In
spite of the initially higher compatibility of the S-DVER-CTBN system with respect to the
S-DVER-VTBN system, the reactivity of the vinyl-ended elastomer leads to a much finer
distribution of the elastomeric phase. In particular, the low molecular weight resin cured
with S and modified with 10% of CTBN leads to a cocontinuous structure with microvoids
that generates a material of low density and poor mechanical and fracture properties. On
the other hand, the use of VTBN as additive leads to a more compact morphology, with
gradual reduction of the mechanical performance of the modified resins and improved
fracture behavior. C 2002 Kluwer Academic Publishers