The rheological and extrusion behaviour of blends based on phenolphthalein poly(ether-ether-sulfone) and thermotropic liquid crystalline polymer

A novel engineering thermoplastic, phenolphthalein poly (ether-ether-sulfone) (PES-C) was blended with a commercial thermotropic liquid crystalline polymer(TLCP), Vectra A950, up to 30 weight percent of TLCP. A rheometrics dynamic spectrometer (RDS-I) and a CEAST capillary rheometer, a rheoscope 1000 were employed to investigate the melt rheology and extrusion behaviour at both the low and high shearing rates. The morphologies of the blends under different shearing were observed with a scanning electron microscope(SEM) and correlated to the observed rheology. The principal normal stress differences measured with cone-and-plate geometry give a temperature-independent correlation for both blend and PES-C when they are plotted against shear stress. But the extrudate swell of the blends showed a strong temperature dependence at each shear stress. The concentration dependence of extrudate swell shows a contrary behaviour to that of the inorganic filled system. A reasonable hypothesis based on the relaxation and disorientation of TLCP during flowing in the capillary and exiting was given to explain it. The melt fracture was checked after extrusion from capillary and was discussed.

Synthesis and characterization of poly(amide imide)s containing cyclohexylidene moieties with bulky substituents

Novel poly(amide imide)s (PAI) containing alkyl-substituted cyclohexylidene moieties were synthesized by conventional polycondensation of trimellitic anhydride chloride with novel aromatic diamines followed by chemical imidization using acetic anhydride and pyridine. The inherent viscosities of the resulting PAIs are relatively high and range from 71 to 112 mt g(-1). The prepared PAIs show excellent thermal stability and good solubility. The glass transition temperatures (T-g) measured by DSC are observed in the range of 312-342 degrees C. Furthermore, all the polymers are readily soluble in less hygroscopic organic solvents like cyclohexanone, gamma-butyrolactone as well as aprotic polar solvents.

Crystallization and melting behavior of nylon 66 poly(ether imide) blends

Isothermal crystallization and melting behavior of nylon 66 and its blends with poly(ether imide) (PEI) were investigated by differential scanning calorimetry. Crystallization kinetics such as overall rate constant Z and index n were calculated according to Avrami approach. Crystallization in the blend was retarded with respect to that of pure nylon 66 by incorporation of PEI with high glass transition temperature (T-g). The lowest growth rate of the spherulites was observed in the blends containing 10 and 15 wt% fraction of PEI. A transition temperature where positively birefringent spherulites disappear and negative birefringent spherulites develop was measured by thermal analysis. The transition temperature increased with content of PEI in the blends. A suitable range of isothermally crystallization temperatures, 238.5-246 degrees C, is suggested For determining the equilibrium melting points by means of Hoffman-Weeks approach.

Miscibility and specific interactions in poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) and poly(P-vinylphenol) blends

The blends of poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) (P(HB-co-HV)/poly(p-vinylphenol)(PVPh) were investigated by differential scanning calorimetry (DSC), Fourier transform IR (FT-IR) spectroscopy and high-resolution solid-state C-13 NMR techniques. Single glass transition temperatures existing in the whole composition range indicates that these blends are miscible. The presence of hydrogen bonding between the hydroxyl of PVPh and carbonyl of P(HB-co-HV), shown by FT-IR spectra, is the origin of the miscibility. Furthermore, results obtained by high-resolution solid-state C-13 NMR give more information about the structure of the blends. (C) 1998 Elsevier Science Ltd. All rights reserved.

The synthesis and characterization of the novel poly(aryl ether ketone)s with liquid crystallinity

The novel poly(aryl ether ketone)s with liquid crystallinity were synthesized by nucleophilic substitution reactions of 4,4'-biphenol and substituted hydroquinone with 4,4'-difluorobenzophenone and their thermotropic liquid crystalline properties were characterized by DSC, PLM and WAXD, The copolymers containing 70% biphenol formed nematic phase while the copolymer containing 50% biphenol exhibited smectic texture, The banded textures were formed after shearing the sample in the nematic liquid crystalline state. The identification of the structures in each mesogenic phase has been carried out by combining WAXD with PLM and DSC.

Influence of annealing on structure of poly(aryl ether ether ketone ketone) revealed by SAXS

Structural studies of poly(aryl ether ether ketone ketone) (PEEKK) using small-angle X-ray scattering and one-dimensional electron density correlation function methods revealed that its aggregated state structure was significantly influenced by the annealing temperature. The long period L, the average thickness of the lamellae d, the electron density difference between the crystalline and amorphous regions eta(c) - eta(a), and the invariant Q increased with increasing annealing temperature, but it was opposite to the case of the specific inner surfaces O-s. A transition zone existed between the traditional "two phases" with a dimension about 0.5 nm for semicrystalline PEEKK. (C) 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1829-1835, 1998.

Preparation and characterization of phenoxy resin/poly(4-vinylpyridine) interpolymer complexes

The compositions and structures of interpolymer complexes formed by mixing phenoxy resin (PHEB) and poly (4-vinylpyridine) (P4VPy) in chloroform have been studied by means of elemental analysis, DSC, FTIR, UV and XPS, In the meantime, the corresponding blends prepared have been characterized and compared. The results show that compositions of the complexes were identical with the ratio of equimolar interactive units. All blends were miscible and their compositions were related to the feed ratios. Based on the experimental results, process of formation of the complex is depicted.

Thermodynamics of blends of poly(ethylene oxide) with poly(methyl methacrylate) and poly(vinyl acetate): prediction of miscibility based on Flory solution theory modified by Hamada

Flory solution theory modified by Hamada et al. (Macromolecules, 1980, 13, 729) was used to predict the miscibility of blends of poly(ethylene oxide) with poly(methyl methacrylate) (PEO-aPMMA) and with poly(vinyl acetate) (PEO-PVAc). Interaction parameters of a PEO-aPMMA blend with the weight ratio of PEO/aPMMA = 50/50 at the temperature range of 393-433 K and PEO-PVAc blends with different compositions and temperatures were calculated from the determined equation-of-state parameters based on Flory solution theory modified by Hamada ed al. Results show that interaction parameters of the PEO-aPMMA blend are negative and can be comparable with values obtained from neutron-scattering measurements by Ito et al. (Macromolecules, 1987, 20, 2213). Also, interaction parameters and excess volumes of PEO-PVAc blends are negative and increase with enhancing the content of PEO and the temperature. (C) 1998 Elsevier Science Ltd. All rights reserved.

Blue-light emitting diodes and flat display based on poly(p-phenylenevinylene) copolymers

Copolymers containing alternating flexible aliphatic blocks and rigid poly(p-phenylenevinylene) (PPV) blocks were synthesized and characterized. It was found that the fluorescent intensity increases with increasing length of the flexible blocks. Bright blue-light emitting diodes were fabricated using PPV copolymers as electroluminescent layers. The devices show 190 cd/m(2) light-emitting brightness at 460 nm and 15 V rum-on voltage. The effects of oxadiazole derivative PBD and tris(8-hydroxyquinoline) aluminum Alq(3) electron-transporting layers on the luminance and stability of the devices are discussed.

Synthesis and characterization of diblock copolymer of butadiene and 2-ethyl-2-oxazoline

By mechanism-transformation (anionic --> cationic) polymerization, diblock copolymer of butadiene and 2-ethyl-2-oxazoline (PBd-b-PEOx) was synthesized in two steps. The first step is the polymerization of butadiene block capped with ethylene oxide and its tosylation; the second step is the cationic ring-opening polymerization of 2-ethyl-2-oxazoline. The products were characterized by various methods, such as IR, (HNMR)-H-1, DMA, TEM and SAXS. The results show that the obtained copolymers possess high molecular weight and narrow molecular weighs distribution, and that the content of 1,4-structure was controllable.

Novel morphology in ring-banded spherulites from single-phase mixtures of poly(epsilon-caprolactone) with poly(styrene-co-acrylonitrile)

Novel morphology of ring-banded spherulites in the surface of poly(epsilon-caprolactone)/poly(styrene-co-acrylonitrile) (PCL/SAN) blends was discovered and studied by SEM and TEM. The ring-banded spherulites separate into those exhibiting a very dark contrast, of relatively regular bundles of lamellae and others appearing with a much brighter intensity, of a coarse and irregular aggregates of lamellae. The origin of the novel morphology is not due to different crystalline structures as in the case of isotactic polypropylene because only one crystal structure exists in PCL/SAN blends. The formation may reflect whether spherulites in PCL/SAN blends are nucleated at the bottom surface or at the top (free) surface.

Nonisothermal crystallization kinetics of poly(beta-hydroxybutyrate)

Kinetics of nonisothermal crystallization of poly( beta-hydroxybutyrate) from melt and glassy states were performed by differential scanning calorimetry under various heating and cooling rates. Several different analysis methods were used to describe the process of nonisothermal crystallization. The results showed that both Avrami treatment and a new method developed by combining the Avrami equation and Ozawa equation could describe this system very well. However, Ozawa analysis failed. By using an evaluation method, proposed by Kissinger, activation energies have been evaluated to be 92.6 kJ/mol and 64.6 kJ/mol for crystallization from the glassy and melt state, respectively. (C) 1998 John Wiley & Sons, Inc.

Several new phenomena in the formation of ring-banded spherulites of poly(epsilon-caprolactone) and poly(styrene-random-acrylonitrile) blends

Ring-banded spherulites in crystallization of poly(epsilon-caprolactone) and poly (styrene-random-acrylonitrile) blends were observed with polarizing optical microscopy and digital image analysis technique was applied directly to the image obtained by polarizing microscope, Several new interesting phenomena were found. One is that the ring-banded structure is still clearly seen after the analyzer was removed and this astonished phenomenon couldn't result from the general concept about formation mechanism of ring-banded spherulite - lamellae twisting, Another one is that there is a slight, dark line in the bright band when cross polars were added, which may be related to the formation process and mechanism of ring-banded spherulites in the blends of poly (epsilon-caprolactone) and poly (styrene-random-acrylonitrile).

Novel poly(aryl ether ketone)s exhibiting liquid crystallinity

Novel poly(aryl ether ketone)s were synthesized by nucleophilic substitution reactions of difluoromonomer with 4,4'-biphenol and substituted hydroquinone. The results showed that the novel polymers exhibited multiple phase transitions and formed optical birefringence textures above their melting transitions.