Melt rheological properties of polypropylene-polyarnide6 blends compatibilized with maleic anhydride-grafted polypropylene

The melt rheological properties of binary uncompatibilized polypropylene -polyamide6 (PP-PA6) blends and ternary blends compatibilized with maleic anhydride-grafted PP (PP-PP-g-MAH-PA6) were studied using a capillary rheometer. The experimental shear viscosities of blends were compared with those calculated from Utracki's relation. The deviation value delta between these two series of data was obtained. In binary PP-PA6 blends, when the compatibility between PP and PA6 was poor, the deformation recovery of dispersed PA6 particles played the dominant role during the capillary flow, the experimental values were smaller than those calculated, and delta was negative. The higher the dispersed phase content, the more deformed the droplets were and the lower the apparent shear viscosity. Also, the absolute value of delta increased with the dispersed phase composition. In ternary PP-PP-g-MAH-PA6 systems, when the compatibility between PP and PA6 was enhanced by PP-g-MAH, the elongation and break-up of the dispersed particles played the dominant role, and the experimental values were higher than calculated. It was observed that the higher the dispersion of the PA6 phase, the higher the delta values of the ternary blends and the larger the positive deviation.

Influence of rubber content in ABS in wide range on the mechanical properties and morphology of PC/ABS blends with different composition

A series of acrylonitrile-butadiene-styrene (ABS) with different rubber content were prepared by diluting ABS grafting copolymer containing 60% rubber with a styrene-acrylonitrile copolymer. ABS prepared were blended with bisphenol-A-polycarbonate (PC) at the ratio of 70/30, 50/50, and 30/70 to prepare PC/ABS blends. Influence of rubber content in ABS on the properties of ABS and PC/ABS blends were investigated. PC/ABS blends with different compositions got good toughness when the rubber in ABS increased to the level that ABS itself got good toughness. The tensile properties and processability of PC/ABS blends decreased with the increase of the total rubber content introduced into the blends. ABS with the rubber content of 30 wt% is most suitable to be used to prepare PC/ABS blends. The rubber content in ABS affected the viscosity of ABS, and subsequently the viscosity ratio of PC to ABS. As a result, the morphology of PC/ABS blends varied. The increase of rubber content in ABS results in finer structure of PC/ABS blends.

Rheological properties in blends of poly(aryl ether ether ketone) and liquid crystalline poly(aryl ether ketone)

Rheological properties of the blends of poly(aryl ether ether ketone) (PEEK) with liquid crystalline poly(aryl ether ketone) containing substituted 3-trifluoro-methylbenzene side group (F-PAEK), prepared by solution precipitation, have been investigated by rheometer. Dynamic rheological behaviors of the blends under the oscillatory shear mode are strongly dependent on blend composition. For PEEK-rich blends, the systems show flow curves similar to those of the pure PEEK, i.e., dynamic storage modulus G' is larger than dynamic loss modulus G", showing the feature of elastic fluid. For F-PAEK-rich systems, the rheological behavior of the blends has a resemblance to pure F-PAEK, i.e., G" is greater than G', showing the characteristic of viscous fluid. When the PEEK content is in the range of 50-70%, the blends exhibit an unusual rheological behavior, which is the result of phase inversion between the two components. Moreover, as a whole, the complex viscosity values of the blends are between those of two pure polymers and decrease with increasing F-PAEK content. However, at 50% weight fraction of PEEK, the viscosity-composition curves exhibit a local maximum, which may be mainly attributed to the phase separation of two components at such a composition.

Dispersion copolymerization of acrylamide with acrylic acid in an aqueous solution of ammonium sulfate: Synthesis and characterization

Dispersion copolymerization of acrylamide with acrylic acid in an aqueous solution of ammonium sulfate using poly(2-acrylamido-2-methylpropanesulfonic acid sodium) as the stabilizer and ammonium persulfate (APS) as the initiator was investigated. The influence of initiator concentration, stabilizer concentration, ammonium sulfate concentration, chain-transfer agent concentration, and polymerization temperature on the copolymerization was discussed. The results showed that varying the ammonium sulfate concentration could affect the particle size and the intrinsic viscosity of the copolymer significantly. With increasing the stabilizer concentration, the particle size of the copolymer decreased first, and then increased, meanwhile the intrinsic viscosity of the copolymer decreased. The increase of initiator concentration, chain-transfer agent concentration, and polymerization temperature resulted in the increase in the particle size. Polydisperse spherical particles were formed in the system, and the kinetics for the dispersion copolymerization were discussed.

Morphology and melt rheology of nylon 11/clay nanocomposites

Nylon 11 (PA11)/clay nanocomposites have been prepared by melt-blending, followed by melt-extrusion through a capillary. Transmission electron n-Licroscopy shows that the exfoliated clay morphology is dominant for low nanofiller content, while the intercalated one is prevailing for high filler loading. Melt rheological properties of PA11 nanocomposites have been studied in both linear and nonlinear viscoelastic response regions. In the linear regime, the nanocomposites exhibit much higher storage modulus (G') and loss modulus (G") values than neat PAIL The values of G' and G" increase steadily with clay loading at low concentrations, while the G' and G" for the sample with 5 wt % clay show an inverse dependence and lie between the modulus values of the samples with 1 and 2 wt % of clay. This is attributed to the alignment/orientation of nanoclay platelets in the intercalated nanocomposite induced by capillary extrusion. In the nonlinear regime, the nanocomposites show increased shear viscosities when compared with the neat resin. The dependence of the shear viscosity on clay loading has analogous trend to that of G' and G".

New neutral nickel(II) complexes bearing pyrrole-imine chelate ligands: synthesis, structure and norbornene polymerization behavior

New neutral nickel(II) complexes bearing nonsymmetric bidentate pyrrole-imine chelate ligands (4a-d), [2-(ArNCH)C4H3N]Ni(PPh3)Ph [Ar=2,6-diisopropylphenyl (a), 2-methyl-6-isopropylphenyl (b), 2,6-diethylphenyl (c), 2-tert-butylphenyl (d)], have been prepared in good yields from the sodium salts of the corresponding ligands and trans-Ni(PPh3)(2)(Ph)Cl, and the structure of complex 4a has been confirmed by X-ray crystallographic analysis. These neutral Ni(II) complexes were investigated as catalysts for the vinylic polymerization of norbornene. Using modified methylaluminoxane (MMAO) as a cocatalyst, these complexes display very high activities and produce great mass polymers. Catalyst activity of up to 4.2 x 10(7) g (mol Ni h)(-1) and the viscosity-average molecular weight of polymer of up to 9.2 x 10(5) g mol(-1) were observed. Catalyst activity, polymer yield, and polymer molecular weight can be controlled over a wide range by the variation of reaction parameters such as Al-Ni ratio, norbornene-catalyst ratio, monomer concentration, polymerization reaction temperature and time.

A polytetrafluoroethylene capillary viscometer

A polytetrafluoroethylene(PTFE) capillary Ubbelohde viscometer was designed and constructed. The relative viscosities of aqueous solutions of a polyethylene oxide and a polyvinylpyrrolidone sample were carefully determined down to an extremely dilute concentration region. In comparison with the data obtained from the common glass capillary viscometer, slippage is believed to occur in the PTFE capillary due to its hydrophobic nature. While for the glass capillary viscometer, conventional viscous flow is operative and adsorption phenomena occur since both the solvent water and aqueous solution are wet and/or adsorbed onto the glass capillary surface due to the existence of hydroxyl groups on glass surface. The data were analyzed with a recently developed wall-effect theory and satisfactory results were obtained.

Reactive compatibilization of polyamide 6 with isocyanate functionalized ethylene-propylene copolymer

Reactive compatibilization of ethylene-propylene copolymer functionalized with allyl (3-isocyanato-4-tolyl) carbamate (TAI) isocyanate (EPM-g-TAI) and polyamide 6 (PA6) was investigated in this paper, FTIR analysis revealed the evidence of a chemical reaction between the end groups of PA6 and EPM-g-TAI. Thermal, rheological, morphological, and mechanical properties of the resultant system were examined, DSC analysis indicated that the crystallization of PA6 in Pa6/EPM-g-TAI blends was inhibited, due to the chemical reaction that occurs at the interface of PA6 and EPM-g-TAI. Rheological measurement showed that complex viscosity and storage modulus of PA6/EPM-g-TAI were both dramatically enhanced compared to those of PA6/EPM at the same blending composition. After examining the morphology of both blending systems, smaller particile sizes, more homogeneous distribution of domains and improved interfacial adhesion between matrix and domains were observed in the compatibilized system. Mechanical properties such as tensile strength. Young's modulus, flexural strength and modulus, as well as notched and un-notched impact strength of PA6/EPM-g-TAI blends were also found to improve gradually with increasing the content of grafted TAI.

Functionalization of an ethylene-propylene copolymer with allyl (3-isocyanate-4-tolyl) carbamate

An ethylene-propylene copolymer (EPM) was functionalized with an iso cyanate-bearing unsaturated monomer, allyl(3-isocyanate-4-tolyl) carbamate (TAI), with dicumyl peroxide as an initiator in a xylene solution. Fourier transform infrared (FTIR) was used to confirm the formation of EPM-g-TAI. The peak at 2273 cm(-1), characteristic of -NCO groups in EPM-g-TAI, revealed evidence of grafting. The grafting degree was determined with both chemical titration and FTIR. The grafting degree could be adjusted, and the maximum was over 6 wt % without any gelation. The molar mass distribution of EPM-g-TAI was narrower than that of EPM. The rheological behavior of both EPM-g-TAI and EPM was investigated with a rotational rheometer. The apparent viscosity of EPM-g-TAI was higher than that of EPM and increased with an increasing grafting degree of TAI. Surface analysis by contact-angle measurements showed that contact angles of EPM-g-TAI samples to a given polar liquid decreased with an increasing grafting degree of TAI. We also obtained the dispersion component of the surface free energy (gamma(S)(d)), the polar component of the surface free energy (gamma(S)(d)), and the total surface free energy (gamma(S) = gamma(S)(d) + gamma(S)(p)) of the grafted EPM. These parameters increased with the enhancement of the grafting degree, which gave us a quantitative estimation of the polar contribution of the grafted TAI to the total surface free energy of EPM-g-TAI.

Novel polyimides derived from 2,3,3 ',4 '-benzophenonetetracarboxylic dianhydride

A series of polyimides (PIs) based on 2,3,3',4'-benzophenonetetracarboxylic dianhydride (2,3,3',4'-BTDA) and 3,3',4,4'-BTDA were prepared by the conventional two-step process. The properties of the 2,3,3',4'-BTDA based polyimides were compared with those of polyimides prepared from 3,3',4,4'-BTDA. It was found that PIs from 2,3,3,4'-BTDA have higher glass transition temperature and better solubility without sacrificing their thermal properties. Furthermore the theological properties of PMR-15 type polyimide resins based on 2,3,3',4'-BTDA showed lower melt viscosity and wider melt flow region (flow window) compared with those from 3,3',4,4'-BTDA. The structure-property relations resulted from isomerism were discussed.

Polyimides from isomeric oxydiphthalic anhydrides

2,2',3,3'-Oxydiphthalic dianhydride (2,2',3,3'-ODPA) and 2,3,3',4'-ODPA were synthesized from 3-chlorophthalic anhydride with 2,3-xylenol and 3,4-xylenol, respectively. Their structures were determined via single-crystal X-ray diffraction. A series of polyimides derived from isomeric ODPAs with several diamines were prepared in dimethylacetamide (DMAc) with the conventional two-step method. Matrix-assisted laser desorption/ionization time-of-flight spectra showed that the polymerization of 2,2',3,3'-ODPA with 4,4'-oxydianiline (ODA) has a greater trend to form cyclic oligomers than that of 2,3,3',4'-ODPA. Both 2,2',3,3'-ODPA and 2,3,3',4'-ODPA based polyimides have good solubility in polar aprotic solvents such as DMAc, dimethylformamide, and N-methylpyrrolidone. The 5% weight-loss temperatures of all polyimides were obtained near 500 degreesC in air. Their glass-transition temperatures measured by dynamic mechanical thermal analysis or differential scanning calorimetry decreased according to the order of polyimides on the basis of 2,2',3,3'-ODPA, 2,3,3',4'-ODPA, and 3,3',4,4'-ODPA. The wide-angle X-ray diffraction of all polyimide films from isomeric ODPAs and ODA showed some certain extent of crystallization after stretching. Rheological properties revealed that polyimide (2,3,3',4'-ODPA/ODA) has a comparatively lower melt viscosity than its isomers, which indicated its better melt processability.

Cationic cyclization of neoprene with a diethylaluminum chloride and organic chloride catalyst system

The cyclization of neoprene was achieved with the aid of a cationic catalyst system based on diethylaluminum chloride (Et2AlCl) and an organic chloride, allyl chloride (CH2=CHCH2Cl) or benzyl chloride (C6H5CH2Cl). The main parameters of the cyclization process were investigated. Elastomers with low intrinsic viscosity, ready solubility and some gelling were obtained. Xylene was a good solvent for the cyclization process, which took place in a very short time (less than or equal to5 min). The products were characterized with IR, H-1-NMR, differential scanning calorimetry, and gel permeation chromatography. The polycyclic structure was determined. The degree of cyctization and the incorporated solvent content were estimated with a H-1-NMR method.

Vinylic polymerization of norbornene by neutral nickel(II)-based catalysts

Neutral Ni(II) salicylaldiminato complexes activated with modified methylaluminoxane as catalysts were used for the vinylic polymerization of norbornene. Catalyst activities of up to 7.08 x 10(4) kg(pol)/(mol(Ni) (.) h) and viscosity-average molecular weights of polymer up to 1.5 x 10(6) g/mol were observed at optimum conditions. Polynorbornenes are amorphous, soluble in organic solvents, highly stable, and show glass-transition temperatures around 390 degreesC. Catalyst activity, polymer yield, and polymer molecular weight can be controlled over a wide range by the variation of the reaction parameters such as the Al/Ni ratio, monomer/catalyst ratio, monomer concentration, polymerization reaction temperature, and time.

Silane bridged polymerized metallocene catalyst for ethylene polymerization

The polymerized metallocene catalyst 4 was prepared by the co-polymerization of ansa-zirconocene complex [CH3Si(2)]ZrCl2 (3) containing vinyl substituted silane bridge with styrene in the presence of radical initiator. Catalyst 4 was found to display high ethylene polymerization activity of 2.28 x 10(6) g PE/(mol . h) with a viscosity average molecular weight (M-eta) value of 61.6 x 10(3) using methylalumoxane (MAO) as a co-catalyst. The ethylene polymerization has been investigated under different conditions.

Oriented crystallization process of polypropylene fractions

Melting recrystallization processes of melt-sheared films of polypropylene (S28C) fractions have been investigated in situ by polarized optical microscope equipped with CCD camera and hot-stage. Actually, the morphological developments in the melting recrystallization are partially reappearance of oriented crystallization processes during melt-shearing the fractions, which is due to a memory effect of oriented structure of polymer. For low molecular weight fraction, only incomplete spherulites with some orientation along shear direction are observed in the melting recrystallization processes of the sheared films. For middle molecular weight fractions, extended chain fiber crystals(or bands) are formed first at higher temperatures, and the bands can act as self-nuclei (i. e., row nuclei), resulting in epitaxial growth of chain-folded lamellae(or fibril), i. e., the formation of cylindrites, with further decrease of the crystallization temperature. For high molecular weight fraction, however, it is not possible to shear the melt film because of its high melt viscosity. When the low molecular weight fraction in which no fiber crystals or cylindrites are observed, are mixed with small amount(about 1%-2%) of the high molecular weight fraction, quite large number of cylindrites are formed during the melting recrystallization process of its sheared film, which implies that the component of high molecular weight plays an important role in the formation of cylindrites during the shear process of polypropylene.