In situ compatibilization of polystyrene and polyurethane blends by using poly (styrene-co-maleic anhydride) as reactive compatibilizer

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. (C) 2001 John Wiley & Sons, Inc.82102514252

Poly(vinyl alcohol) and poly(vinyl pyrrolidone) blends: Miscibility, microheterogeneity and free volume change

Blends of crystallizable poly(vinyl alcohol) (PVA) with poly(vinyl pyrrolidone) (PVP) were studied by differential scanning calorimetry (d.s.c.). PVA with different degrees of hydrolysis (88 and 99 wt%) and PVP with different molecular weights (10 000 and 360 000 g mol(-1)) were used. The blends exhibited a single glass transition, as determined by d.s.c., suggesting the miscibility of the system over the whole composition range studied. The enthalpy of fusion (Delta H-f), as well as the glass transition temperature (T-g), heat capacity (Delta C-p) and glass transition width (Delta w), were also determined by d.s.c. These parameters changed with the degree of hydrolysis of PVA, PVP molecular weight and blend composition. The behaviour of Delta C-p vs blend composition was complex for the different pairs of blends, suggesting strong interaction between PVA and PVP. From the analysis of Delta w dependence on blend composition we concluded that blends containing PVP of 10 000 g mol(-1) exhibit a larger number of relaxations than blends containing high molecular weight PVP, indicating that the density of interactions is larger in the former. (C) 1997 Elsevier Science Ltd.38153907391

Poly(vinyl alcohol) and poly(vinylpyrrolidone) blends: 2. Study of relaxations by dynamic mechanical analysis

Blends of poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) were studied by dynamic-mechanical analysis (DMA). PVA with different degrees of hydrolysis (88 and 99 wt%) and PVP with different molecular weights (10.000 and 360.000 g/mol) were used to prepare the blends. DMA results showed that blends were miscible over the whole composition range studied. However, the E' modulus curves exhibit relaxations at the same temperature range below Tg for all blends, suggesting the presence of microenvironments in the blends. These microenvironments are associated to the hydrogen bonding between PVA-PVA in the crystalline and amorphous phase and PVP-PVA in the amorphous phase and in the amorphous-crystalline interface. The stiffness and the flexibility of these blends at 200 degrees C depend strongly on the blends composition, the molecular weight of PVP and the hydrolysis degree of the PVA as determined by the E' modulus curves. (C) 1999 Elsevier Science Ltd. All rights reserved.40174845485

Polystyrene and polyether polyurethane elastomer blends compatibilized by SMA: Morphology and mechanical properties

Blends of polystyrene (PS) and the polyether polyurethane elastomer (PU-et) were prepared by melt mixing using poly(styrene-co-maleic anhydride) (SMA) containing 7 wt % of maleic anhydride as a compatibilizer. The polyurethane in the blends was crosslinked using dicumyl peroxide or sulfur, The content of maleic anhydride was varied in the blends through the addition of different SMA amounts. The morphology of the blends was analyzed by SEM and a drastic reduction of both the domain size and its distribution was observed with increase of the anhydride content in the blends. The morphology of the PU-et blends also showed dependence on the crosslinker agent used for the elastomer, and larger domains were obtained for the clastomer phase crosslinked with dicumyl peroxide. The mechanical properties of the blends were evaluated by flexural and impact strength tests. The blend containing 0.5 wt % of maleic anhydride and 20 wt % of PU-et crosslinked with sulfur showed the highest strength impact, which was three times superior to the PS strength impact, and the blends containing 20 wt % of PU-et crosslinked with dicumyl peroxide showed the highest deflection at break independent of the anhydride content. (C) 2002 John Wiley & Sons, Inc. J Appl Polym Sci 83: 830-837, 2002.83483083

Polystyrene and polyester polyurethane elastomer blends compatibilized by SMA

Blends of polystyrene (PS) with polyester polyurethane elastomer (PU-es) were compatibilized by addition of poly(styrene-co-maleic anhydride) (SMA) containing 7 wt % of maleic anhydride. Binary nonreactive (PS/PU-es) blends, binary reactive (SMA/PU-es) blends, and ternary reactive blends (PS/SMA/PU-es) were prepared with 10 and 20 wt % of PU-es. The maleic anhydride content in the ternary reactive blends was varied through addition of different SMA amounts from 0.5 to 5 wt %. Polyurethane in the blends' vas crosslinked by using dicumyl peroxide or sulfur to improve its mechanical properties. The experimental processing conditions, such as temperature and rotor speed in an internal mixer, were analyzed before blend preparation by processing the individual polymers, PS and SMA, and the PS/PU-es nonreactive blend (90/10), to prevent the degradation of the polymer during melt mixing and to assure macroscopic homogeneity. The torque behavior during the mixture indicated a grafting copolymerization, which was responsible for the significant drop of the PU-es domain size in the glassy matrix, as observed by scanning electronic microscopy (SEM). The miscibility of the glassy matrix, which was shown to be dependent on the composition and the phase behavior of ternary blends, became very complex as the SMA concentration increased, as concluded from dynamical-mechanical analysis. Blends containing 20 wt % of PU-es presented an increase up to a factor of 2 in the deflection at break in relation to PS. (C) 2004 Wiley Periodicals, Inc.9352297230

Thermal stability of polycaprolactone/Nafion blends prepared in the presence of 3-aminopropyltriethoxysilane

Polycaprolactone (PCL) and Nafion blends were prepared in the presence of 3-aminopropyltriethoxysilane (3-APTEOS) by a sol-gel reaction. The presence of 3-APTEOS allowed the preparation of macroscopically homogeneous self-supported films of PCL/Nafion blends in a wider composition range. The thermal properties of the blends were evaluated by thermogravimetric analysis and differential scanning calorimetry. The thermal stability of the blends decreased as the Nafion content increased. The reduction of the thermal stability of PCL in the presence of Nafion was confirmed with Fourier transform infrared/photoacoustic spectroscopy, and it was attributed to the possible hydrolysis of PCL caused by the reaction with the SO3H acid groups of Nafion. An opposite effect on the thermal stability of the blends was caused by the addition of 3-APTEOS. The increase in the thermal stability of the blends with the increase in the 3-APTEOS content was assigned to the neutralization of the acid groups of Nafion by the formation of an ionic complex. The differential scanning calorimetry results showed that PCL and Nafion were immiscible. The degree of crystallinity of PCL slightly increased with an increase in the Nafion content, whereas the melting temperature remained basically unchanged. (C) 2004 Wiley Periodicals, Inc.9263701370

Structure and morphology of poly(epsilon-caprolactone)/chlorinated polyethylene (PCL/PECl) blends investigated by DSC, simultaneous SAXS/WAXD, and elemental mapping by ESI-TEM

In this work, the structure and morphology of miscible blends of poly(epsilon-caprolactone) and chlorinated polyethylene with 48% chlorine weight content (PCL/PECl) were studied by differential scanning calorimetry (DSC), simultaneous small and wide-angle X-ray scattering (SAXS/WAXD), and electron spectroscopy imaging in the transmission electron microscope (ESI-TEM). A unique glass transition temperature was obtained in each blend. In addition to this, the heat capacity and the width of the glass transition did not have a linear behavior with blend compositions. These facts correlate with the presence of microheterogeneities originated from different local compositions and densities of interactions in each blend. A consistent picture of the mode of segregation of PECl in the blend was obtained. For higher concentration of PCL, the volume fraction of lamellar stacks in the samples decreased as a function of the PECl content, indicating preferential interfibrillar localization of the amorphous component. For lower PCL concentration, interespherulitic segregation was the dominant mode. Elemental maps of chlorine confirmed these results and also revealed changes in the concentration of this element depending on its localization in the microstructure of the system. Gradients of chlorine concentration were measured in larger amorphous regions of the 40/60 and 20/80 PCL/PECl blends. Calculations of the one-dimensional correlation function probed the reduction of the lamellar thickness of PCL when the quantity of PECl in the blend was increased. Such a tendency could be rationalized if the reduction of the fold surface free energy was a dominant factor in terms of the reduction of the degree of supercooling in the final crystal thickness.40225326