Abstract

Abstract

Abstract

Amphiphilic graft copolymers consisting of poly(phthalazinone ether sulfone ketone) (PPESK) backbones and poly(ethylene glycol) (PEG) side chains were synthesized via reaction of chloromethylated PPESK (CMPPESK) with a sodium alkoxide of methoxyl PEG (PEG- ONa). The reactive precursor, CMPPESK, was prepared by the chloromethylation of PPESK with chloromethylether (CME) using concentrated H₂SO₄ as reaction medium. FTIR spectroscopy, ¹H-NMR and Solid-state ¹³C CP-MAS NMR analysis confirmed the covalent linking of PEG with PPESK backbones. The PEG content in the graft copolymers from ¹H-NMR analysis varied from 21.0 to 37.2 wt %, which was approximately in agreement with that calculated from TGA tests. The graft products have good solubility in many aprotic polar solvents and can be slightly swelled by water and ethanol, but water insoluble. Contact angle measurements revealed that the hydrophilicity of PPESK was significantly improved by the introduction of PEG graft chains, indicating the graft copolymer is a potential hydrophilic additive for PPESK membranes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007.

In this study, a novel and environmentally friendly extracting method, supercritical carbon dioxide (SC-CO₂) extraction, was investigated in the thermally induced phase separation (TIPS) process for making microporous membranes. In the SC-CO₂ extraction, the effects of extraction time, pressure, and temperature on the extraction fraction, membrane morphology, and membrane performance were investigated. It was concluded that with extraction conditions of 18 MPa, 35°C and 2 h, the porous membrane had the highest extraction fraction. There was a close relationship between membrane performance and the extraction conditions of SC-CO₂, and it is possible to tailor membrane performance through the choice of extraction conditions. Compared with traditional solvent extraction, a dry membrane treated by SC-CO₂ extraction has much less shrinkage and greater water permeability, whereas the degree of crystallization of a membrane extracted by SC-CO₂ is slightly greater than that extracted by ethanol. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1632–1639, 2007

The phase characteristics and morphology of stretched hard elastic poly(vinylidene fluoride) (PVDF) fibers were investigated by X-ray diffraction (XRD) and wide-angle and small-angel X-ray scattering (WAXS and SAXS). It was indicated that α and β phases coexisted in stretched PVDF fibers, stretching assisted in α to β phase transformation. The β/α ratios of stretched PVDF fibers were affected by stretching temperature, rate, and ratio. The β phase content of stretched PVDF fibers had an abrupt increase when stretched near 70°C, and then it decreased with increasing stretching temperature. Besides, the β/α ratio of PVDF fibers increased with stretching rate and ratio. The total crystallinity of PVDF fibers did not change much even on different stretching conditions. WAXS results indicated that the unstretched and stretched PVDF fibers all exhibited three strong equatorial streaks, with d-spacing (0.964, 0.488, and 0.439 nm) and (0.946, 0.494, and 0.480 nm), which suggested that PVDF fibers still remained the crystalline reflections of c-axis orientation even after being stretched. The long periods of stretched PVDF fibers, calculated from SAXS curves, increased from 19.04 to 39.75nm. On the basis of these results, the β transformation mechanism of stretched PVDF fibers was also discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2254–2259, 2007

Poly(vinyl chloride) (PVC) was irradiated by electron beam in vacuum at 20 KGy to produce living free radicals, and then reacted with acrylic acid (AA) in solution to obtain the PVC-g-AA copolymers. The copolymers were characterized by Fourier transform infrared spectroscopy. Porous membranes were prepared from copolymers by the phase inversion technique. The morphology of PVC-g-AA membranes was studied by field emission scanning electron microscopy. The mean pore size and pore size distribution were determined by a mercury porosimeter. The mean pore size was 0.19 μm, and the bulk porosity was 56.02%. The apparent static water contact angle was 89.0°. The water drop penetration rate was 2.35 times to the original membrane. The maximum stress was 4.10 MPa. Filtration experiments were carried out to evaluate the fouling resistance of the PVC-g-AA membrane. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Composite membranes of sulfonated poly (phthalazinone ether ketone)s (SPPEK)s and Zirconium hy drogen phosphate (ZrP) or 12-phosphotungstic acid (PWA) were prepared by direct blending method. The physicochemical properties of these composite membranes were studied through Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy, field-emission scan ning electron microscope (FSEM), X-ray diffraction (XRD) and thermogravimetry analysis (TGA). The SPPEK/PWA composite membranes showed better properties, whose highest proton conductivity could reach 0.17 S/cm at 80°C under 100% relative humidity (R.H.). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3972–3977, 2006

The nonisothermal crystallization kinetics for ultra–high molecular weight polyethylene (UHMWPE) in liquid paraffin (LP) systems was investigated through differential scanning calorimetry (DSC) measurement. The influence of UHMWPE concentration and cooling rate on crystallization mechanism and spherulitc structure as implied by the modified Avrami equation and Mo's analysis was determined, whereas the Ozawa's approach fails to describe the crystallization behaviors of these UHMWPE-diluent systems. As a result, in the modified Avrami analysis, it was found that the Avrami exponent is constant around five at various concentrations of UHMWPE and cooling rates. Further, the value of F(T) in the Mo's approach increases with the increasing of relative crystallinity and UHMWPE content in the blends. The nonisothermal crystallization kinetics presented here are the first for UHMWPE-diluent systems. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006

The cloud points of PPESK/NMP/H₂O ternary system at different temperatures were measured by titrimetric method. The binodal lines in the ternary phase diagram of the poly(phthalazinone ether sulfone ketone (PPESK) dope system was determined, on the basis of the cloud point experimental data being linearly fitted with the semiempirical linear cloud point correlation. Furthermore, phase separation behavior during the phase inversion of PPESK membrane-forming system was discussed in terms of the phase diagram. Then, dry–wet spinning technique was employed in manufacturing PPESK hollow fiber membranes by immersion precipitation method. The cross-section morphologies of hollow fibers were observed by scanning electronic microscopy. Also, the effects of dope solution composition and spinning parameters, including the coagulant composition and the spinning temperature on the separation performances of fibers, were evaluated by permeability measurements. The thermotolerance of the PPESK hollow fiber membranes prepared in the work was examined for the permeation operation at different temperatures and pressure differences. The experimental results showed that pure water flux increases several fold along with the temperature increases from 20 to 80°C at different operation pressures, while the solute rejection only decreases slightly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 878–884, 2006

Summary: Poly(vinylidene fluoride) (PVDF) fibers were prepared by melt-spinning process. The crystal structure of annealed PVDF fibers was characterized by wide- and small-angle X-ray diffraction (WAXD and SAXD) and scanning electron microscopy (SEM). Crystalline reflections of c-axis orientation of annealed PVDF fibers were illustrated by WAXD pattern. The stacked lamellar structure aligned in the direction normal to the fiber axis was found in SAXD pattern and the d-spacing of the lamellae was 13.4 nm. Such lamellar structure was supported by SEM micrographs as well. The elastic recovery of annealed PVDF fibers was above 80% from 50% extension, which was much higher than that of unannealed fibers on the first cycle. The initial elastic modulus of annealed fibers reached to a value of 3.5 GPa. The morphological and mechanical properties, all indicated that the annealed PVDF fibers had the characteristic of hard elasticity. A typical stress-strain curve at a very low strain rate indicated the deformation of crystal lamellae in the fibers and a suggested structural deformation mechanism detailed the characteristics of hard elasticity.

Fe₃O₄/poly(styrene-co-maleic anhydride) core–shell composite microspheres, suitable for binding enzymes, were prepared using magnetite particles as seeds by copolymerization of styrene and maleic anhydride. The magnetite particles were encapsulated by polyethylene glycol, which improved the affinity between the magnetite particles and the monomers, thus showing that the size of the microspheres, the amount of the surface anhydrides, and the magnetite content in the composite are highly dependent on magnetite particles, comonomer ratio, and dispersion medium used in the polymerization. The composite microspheres, having 0.08–0.8 μm diameter and containing 100–800 μg magnetite/g microspheres and 0–18 mmol surface-anhydride groups/g microsphere, were obtained. Free α-amylase was immobilized on the microspheres containing reactive surface-anhydride groups by covalent binding. The effects of immobilization on the properties of the immobilized α-amylase [magnetic immobilized enzyme (MIE)] were studied. The activity of MIE and protein binding capacity reached 113,800 U and 544.3 mg/g dry microspheres, respectively. The activity recovery was 47.2%. The MIE had higher optimum temperature and pH compared with those of free α-amylase and showed excellent thermal, storage, pH, and operational stability. Furthermore, it can be easily separated in a magnetic field and reused repeatedly. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 328–335, 2005

The membrane extraction of copper ions was carried out using hydrophobic poly(propylene) (PP) hollow fiber membrane modules and kerosene solutions containing organic extractant. The influences of different extractant on the extraction yield, mass transfer performance and mass transfer mechanism were studied. Compared with 2-ethylhexyl phosphoric acid (2EHPA) and 2-methyl-5-sulpho benzaldoxime (2M5SB), di-(2-ethylhexyl)phosphoric acid (D2EHPA) extractant system with high distribution coefficient exhibited higher extraction yield of 99.7%. The extraction equilibrium time, the final extraction yield and the total mass transfer coefficient were independent of the flow rates of two phases. The extraction equilibrium time and the final extraction yield at different flow rates of two phases were 80 min and near 99.5%, respectively. A mass transfer model of a complexation reaction describing the overall mass transfer resistance was controlled by interfacial reactions rather than the aqueous and organic boundary layer which could explain the effect of flow rate on the final extraction yield and the total mass transfer coefficient. This model showed that the mass transfer resistance and mass transfer coefficient were independent of Cu²⁺ when copper ion concentration was more than 0.06 g/L. However, when copper concentration was less than 0.06 g/l, the mass transfer resistance increased as Cu²⁺ concentration decreased, and the mass transfer coefficient decreased as Cu²⁺ concentration decreased. Extractant entrainment in the aqueous phase and membrane fouling were investigated primarily. It was found that the solvent entrainment could reduce to 10 ppm much lower than 200 ppm of the classic liquid–liquid extraction, and that the cleaning of contaminated membranes was not complete. However, it can be still concluded from this research that the membrane extraction in PP hollow fibre with D2EHPA extractant would be an effective and promising processing means for Cu²⁺ separation from aqueous solution. Copyright © 2005 John Wiley & Sons, Ltd.