2001 |
In situ Compatibilization of
Polystyrene and Polyurethane Blends by Using Poly (Styrene-co-Maleic Anhydride)
as Reactive Compatibilizer
Cassu SN, Felisberti MI
JOURNAL OF APPLIED POLYMER SCIENCE
82 (10): 2514-2524 DEC 5 2001
Abstract:
Blends of polystyrene (PS) and polyurethane (PU) elastomer were obtained by melt
mixing, using poly(styrene-co-maleic anhydride) (SMA) containing 7 wt % of
maleic anhydride groups as a reactive compatibilizer. Polyurethanes containing
polyester flexible segments, PU-et, and polyether flexible segments, PU-et, were
used. These polyurethanes were crosslinked with dicumyl peroxide or sulfur to
improve their mechanical properties. The anhydride groups of SMA can react with
the PU groups and form an in situ graft copolymer at the interface of the blends
during their preparation. The rheological behavior was accompanied by torque
versus time curves and an increase in the torque during the melt mixing was
observed for all the reactive blends, indicating the occurrence of a reaction.
Solubility tests, gel permeation chromatography, and scanning electronic
microscopy confirmed the formation of a graft copolymer generated in situ during
the melt blending. These results also indicate that this graft copolymer
contains C-C bond between SMA and PU chains.
Unsaturated Polyester Resin Modified
with Poly(Organosiloxanes). I. Preparation, Dynamic Mechanical Properties, and
Impact Resistance
Rosa VM, Felisberti MI
JOURNAL OF APPLIED POLYMER SCIENCE
81 (13): 3272-3279 SEP 23 2001
Abstract:
Unsaturated polyester resins (UP) display a wide range of applications depending
on the proper choice of raw materials and cure conditions. However, some
applications are limited to their low-impact resistance, which can be enhanced
by the incorporation of modifiers that increase the flexibility of the network.
This work aims to incorporate flexible poly(organosiloxane) segments in the UP
network as a graft copolymer, as a way of minimizing the low adhesion between
the resin and the modifier and enhance its flexibility. Because polyester and
poly(organosiloxanes) are immiscible mixtures, the grafting copolymerization
during the cure can promote compatibilization between both polymers. Hence,
glycidyl methacrylate (GMA) is added to the resin network by radical reaction,
as well as 1,3-aminopropyltriethoxysilane (APTS), amino groups of which react
with GMA. The addition of a siloxane
(1,1,3,3-tetramcthyl-1,3-diethoxydisiloxane) allows the poly(organosiloxane)
network to grow and the addition of water guarantees the hydrolysis and
polycondensation during the cure. In this way it is possible to increase its
flexibility. The grafting copolymerization is evaluated by dynamic mechanical
analysis and the impact resistance of pure and modified polyester resins is
evaluated by the Izod test. The grafting of a flexible segment in the UP chains
enhances the impact resistance of the polyester resin at low-modifier
concentration.
Unsaturated Polyester Resin Modified
with Poly(Organosiloxanes). II. Acoustic Emission Study on
Glass-Fiber-Reinforced Resin
Rosa VM, Karger-Kocsis J, Felisberti MI
JOURNAL OF APPLIED POLYMER SCIENCE
81 (13): 3280-3289 SEP 23 2001
Abstract:
This work aims to study the adhesion of an isophthalic acid based unsaturated
polyester resin chemically modified by grafting copolymerization of a poly(organosiloxane)
to the glass fiber. The failure mode of the single-edge notched tensile specimen,
cut from pressed plates containing 50 wt % of nontreated and silane-treated
milled glass fiber, was studied by acoustic emission (AE) technique. It was
found that the aforementioned resin modification enhanced the adhesion between
the fiber and the resin. This was suggested by a shift in the AE amplitude and
energy toward higher values. On the other hand, the matrix modification had no
significant effect if glass fiber with suitable unsaturated polyester resin (UP)
sizing was incorporated.
Miscibility, Crystallinity and
Morphological Behavior of Binary Blends of Poly(Ethylene Oxide) and Poly(Methyl
Vinyl Ether-Maleic Acid)
Rocco AM, Pereira RP, Felisberti MI
POLYMER
42 (12): 5199-5205 JUN 2001
Abstract:
DSC and optical microscopy were used to determine the miscibility and
crystallinity of blends of poly(ethylene oxide) (PEO) with poly(methyl vinyl
ether-co-maleic acid) (PMVE-MAc). Single T-g was observed for all blends,
indicating miscibility. The dependence of T-g on the weight per cent of PEO
presents a negative deviation from linearity at high PEO content, associated to
a greater blend free volume, mobility and flexibility than in pure PEG. A
progressive decrease in the degree of crystallinity and in the size of the PEO
spherullites as the PMVE-MAc is added is observed. FTIR provided evidence of
specific interaction between the polymers.