bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of extraction procedures for arsenic speciation in environmental solid reference materials by high‐performance liquid chromatography–hydride generation‐atomic fluorescence spectroscopy
Authors: Montperrus M. , Bohari Y. , Bueno M. , Astruc A. , Astruc M. 
Published: August 2002

AbstractWater and ‘soft’ extractions (hydroxylammonium hydrochloride, ammonium oxalate and orthophosphoric acid) have been studied and applied to the determination of arsenic species (arsenite, arsenate, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA)) in three environmental solid reference materials (river sediment, agricultural soil, sewage sludge) certified for their total arsenic content. The analytical method used was ion exchange liquid chromatography coupled on‐line to atomic fluorescence spectroscopy through hydride generation. Very low detection limits for arsenic were obtained, ranging from 0.02 to 0.04 mg kg−1 for all species in all matrices studied. Orthophosphoric acid is the best extractant for sediment (mixed origin) and sludge samples (recent origin) but not for the old formation soil sample, from which arsenic is extracted well only by oxalate. Both inorganic forms (As(III) and As(V)) are significant in all samples, As(V) species being predominant. Moreover, organic forms are found in water extracts of all samples and are more important in the sludge sample. These organic forms are also present in the ‘soft’ extracts of sludge. Microwave‐assisted extraction appears to minimize the risk of a redox interconversion of inorganic arsenic forms. This study points out the necessity of combining direct and sequential extraction procedures to allow for initial arsenic speciation and to elucidate the different mineralogical phases–species associations. Copyright © 2002 John Wiley & Sons, Ltd.
Ion aggregation in the polysiloxane ionomers bearing pendant quaternary ammonium groups
Authors: Huang Zuoxin , Yu Yunzhao , Huang Ying 
Published: August 2002

AbstractPolysiloxane ionomers bearing pendant quaternary ammonium groups were synthesized through the Menshutkin reaction of poly(γ‐chloropropylmethylsiloxane‐co‐dimethylsiloxane) with N,N‐dimethylbenzylamine. Ion aggregation in the ionomers with different contents of the quaternary ammonium groups was investigated by torsion braid analysis, transmission electron microscopy, and rheological measurements. It was found that the incorporation of the quaternary ammonium groups did not make a significant effect on the glass transition temperature of the polysiloxane matrix. The glass transition of the cluster phase was found in the range of −20–40°C, depending on the concentration of the ion pair. The cluster phase was visualized under TEM when the concentration of the quaternary ammonium group exceeded a critical value. It was indicated by rheological data that the movement of polymer chains in the cluster phase of the polysiloxane ionomers was not restricted at the room temperature, which might be related to the weaker interaction between the bulky quaternary ammonium ion pairs. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3099–3104, 2002; DOI 10.1002/app.10009
Application of a linear synthetic polymer to improve the properties of cellulose fibers made by the NMMO process
Authors: Lewandowski Z. 
Published: August 2002

AbstractLow‐molecular polyethylene (LMPE) as an internal flexibilizer was selected to improve the spinnability of cellulose solution in N‐methylmorpholine‐N‐oxide (NMMO). It is compatible with the conditions of cellulose dissolution and fiber spinning because of its chemical stability and melting point. In the course of rheological investigations, it was proven that this modification has a physical characteristic. Cross sections of the fibers reveal that cellulose–LMPE forms a two‐phase system with randomly distributed LMPE domains and a dominant skin‐core structure. The addition of 5% LMPE is enough to improve significantly the mechanical properties of the fibers. An increase of LMPE above 5% worsens these properties, because LMPE is not a fiber‐forming polymer. With the use of spinnerets with suitable dimensions, it is possible to obtain cellulose fibers with mechanical properties similar to those of synthetic fibers. The retention of water is lowered by the hydrophobic polyethylene polymer; however, it is high enough to retain the hydrophilic character of cellulose fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2762–2773, 2002; DOI 10.1002/app.10227
Thermal degradation of flax: The determination of kinetic parameters with thermogravimetric analysis
Authors: Van De Velde K. , Kiekens P. 
Published: August 2002

AbstractThe thermal degradation of flax was investigated with thermogravimetric analysis. The flax used for these experiments underwent different stages of retting or, in one case, boiling. The most retted type of flax was also chemically treated to obtain elementary fibers. These samples were all tested in dynamic and isothermal runs after careful sample preparation. The resulting thermograms were analyzed and later used to calculate the kinetic parameters of cellulose degradation. These kinetic parameters included reaction constants and activation energies. A clear difference in the various tested types of flax was observed through a comparison of these values, and an explanation for these differences was suggested. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2634–2643, 2002
Structure and properties of injection‐molded polypropylenes with different molecular weight distribution and tacticity characteristics
Authors: Fujiyama Mitsuyoshi , Kitajima Yoshiyuki , Inata Hitoshi 
Published: August 2002

AbstractTwo series of polypropylenes with different molecular weight distribution and tacticity characteristics were injection molded into flexural test specimens by varying cylinder temperature and the effects of the molecular weight distribution and tacticity on the structure and properties of the moldings were studied. Measured propertied were flexural modulus, flexural strength, heat distortion temperature, Izod impact strength, and mold shrinkage and structures studied were crystallinity, the thickness of skin layer, a*‐axis‐oriented component fraction and crystalline orientation functions. The relations between the structures and properties were also studied. It was found that the molecular weight distribution and tacticity characteristics affect the properties mainly through the molecular orientation and crystallinity, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2142–2156, 2002
Cure reaction for modified diallylbisphenol A/diaminodiphenylsulfone/bismaleimide
Authors: Boey F. Y. C. , Song X. L. , Rath S. K. , Yue C. Y. 
Published: August 2002

AbstractThe glass‐transition temperature as a function of curing conversion for a modified diallylbisphenol A/diaminodiphenylsulfone/bismaleimide (BMI) resin was investigated at different temperature regimes and modeled using a modified Di Benedetto equation. Although the relationship between the glass‐transition temperature and conversion of the BMI system conforms to the Di Benedetto equation for α < 0.6 and at lower cure temperatures, at higher cure temperatures the results deviated significantly from the equation; thus, it was an inadequate model for the system. Fourier transform IR analysis showed that the major crosslinking reactions did not occur during cure for the modified BMI at and below 150°C. However, as the cure temperature was increased, the crosslinking reactions responsible for 3‐dimensional network structures became more dominant. At 190°C the CNCstretch vibration of the uncured maleimide ring converted into succinimide rings in the curing process. Simultaneously, a decrease was observed for the absorbance bands of  CHbending (maleimide). The higher cure temperatures induced a significantly faster initial crosslinking rate and also resulted in a shorter period of time after which further crosslinking was retarded, because the increase in the crosslinks also physically slowed further crosslinking activity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 227–235, 2002
Chemical modification of hemp, sisal, jute, and kapok fibers by alkalization
Authors: Mwaikambo Leonard Y. , Ansell Martin P. 
Published: August 2002

AbstractPlant fibers are rich in cellulose and they are a cheap, easily renewable source of fibers with the potential for polymer reinforcement. The presence of surface impurities and the large amount of hydroxyl groups make plant fibers less attractive for reinforcement of polymeric materials. Hemp, sisal, jute, and kapok fibers were subjected to alkalization by using sodium hydroxide. The thermal characteristics, crystallinity index, reactivity, and surface morphology of untreated and chemically modified fibers have been studied using differential scanning calorimetry (DSC), X‐ray diffraction (WAXRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), respectively. Following alkalization the DSC showed a rapid degradation of the cellulose between 0.8 and 8% NaOH, beyond which degradation was found to be marginal. There was a marginal drop in the crystallinity index of hemp fiber while sisal, jute, and kapok fibers showed a slight increase in crystallinity at caustic soda concentration of 0.8–30%. FTIR showed that kapok fiber was found to be the most reactive followed by jute, sisal, and then hemp fiber. SEM showed a relatively smooth surface for all the untreated fibers; however, after alkalization, all the fibers showed uneven surfaces. These results show that alkalization modifies plant fibers promoting the development of fiber–resin adhesion, which then will result in increased interfacial energy and, hence, improvement in the mechanical and thermal stability of the composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2222–2234, 2002
Fine polystyrene latexes with reactive poly(ethylene oxide) –poly(propylene oxide)–poly(ethylene oxide) triblock macrosurfactants in modified miniemulsion polymerization
Authors: Kim Jin‐Woong , Ko Ji‐Young , Park Jin‐Gyu , Jun Jung‐Bae , Chang Ih‐Seop , Suh Kyung‐Do 
Published: August 2002

AbstractPolystyrene latexes were produced via a newly accessible miniemulsion polymerization where reactive poly(ethylene oxide)–poly(propylene oxide) –poly(ethylene oxide) triblock macrosurfactants were used to impart the interfacial activity during the emulsification and the reactivity in the polymerization. Through atomic force microscopy studies, it was found that the polystyrene latexes produced were extremely small to about 50 nm in a proper experimental condition, and covered richly with poly(ethylene oxide) groups. The polystyrene latexes were expected to have great applicability in the production of structured latex films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 328–332, 2002
Influence of die angles on pressure drop during extrusion of rubber compound
Authors: Liang Ji‐Zhao 
Published: August 2002

AbstractThe factors affecting pressure losses during extrusion of polymer melts are discussed in the present article. The rheological properties of an unvulcanized rubber compound were examined by using a Monsanto processability tester (MPT) under experimental conditions of temperatures varied 90 to 120°C and shear rates from 102 to 103 s−1. Furthermore, a set of dies with different entry angle (2α) was selected to identify the effects of die angles on pressure losses in capillary extrusion of the sample fluid. It was found that the total pressure drop (ΔP) decreased when 2α < 75 degrees, and then increased with increasing 2α. The ΔP reached the minimum value when 2α is around 75°. It suggests that the natural converging angle of the sample fluid be about 75° under the experimental conditions, according to the research results presented in previous work. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1150–1154, 2001
Poly(lactide‐co‐glycolide) solution behavior in supercritical CO2, CHF3, and CHClF2
Authors: Conway S. E. , Byun H.‐S. , McHugh M. A. , Wang J. D. , Mandel F. S. 
Published: August 2002

AbstractCloud point and solution density data between 20 and 100°C and pressures to 3000 bar are presented for poly(lactide) (PLA) and poly(lactide‐co‐glycolide) (PLGAx, where the molar concentration of glycolide in the backbone x ranges from 0 to 50 mol %) in supercritical CO2, CHClF2, and CHF3. PLA dissolves in CO2 at pressures near 1400 bar, in CHF3 at pressures of 500 to 750 bar, and in CHClF2 at pressures of 20–100 bar. As glycolide (GA) is added to the backbone of PLGA, the cloud point pressure increases by 50 bar/(mol GA) in CO2, 25 bar/(mol GA) in CHF3, and by only 2.5 bar/(mol GA) in CHClF2. PLGA50 does not dissolve in CO2 to pressures of 3000 bar whereas it is readily soluble in CHClF2 at pressures as low as 100 bar at 50°C. In comparison, the increases in cloud point pressure with increasing weight average molecular weight (Mw) are only approximately 2.3 bar/(1000 Mw) for PLGA copolymers in CO2. The solution densities with all three SCF solvents range from 1.1 to 1.5 g/cm3 and they vary only by a small amount over the 80°C range used to obtain cloud point data. More than likely, the ability of the acidic hydrogen in CHF3 and CHClF2 to complex with the ester linkage in PLGA makes these better solvents than CO2 especially since any change in favorable energetic interactions is magnified due to the liquid‐like densities exhibited by these SCF solvents. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1155–1161, 2001
Curing and toughening of a styrene‐modified epoxy resin
Authors: Yoon Tae‐Ho , Mcgrath James E. 
Published: August 2002

AbstractA commercially available epoxy resin (E907) formulated with a viscosity‐reducing styrene monomer and several additives was subjected to thermal cure studies and mechanical property measurements. Thermoplastic poly(arylene ether sulfone) (PES) and poly(arylene ether phosphine oxide) (PEPO) with reactive amine or hydroxyl end groups were utilized to toughen and co‐cure with the system. The cure cycle was optimized and the networks were analyzed via differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analyzer, scanning electron microscopy, sol–gel extractions, and fracture toughness. A model epoxy resin was prepared from a tetrafunctional epoxy, e.g., MY722, difunctional EPON828, styrene monomer, and benzoyl peroxide initiator (BPO), and was evaluated as a control to assess the possible role of the styrene monomer. The optimized cure cycle for E907 was 6 h at 93°C, followed by a postcure of 2 h at 204°C. The fracture toughness of E907 was increased only marginally with PES and PEPO. In contrast, the model epoxy resin demonstrated a positive effect due to the styrene monomer and BPO and exhibited significantly increased fracture toughness with PES modification. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1504–1513, 2001
Study of fusion percolation thresholds of rigid PVC compounds
Authors: Chen Cheng‐Ho , Mao Ching‐Feng , Lo Yu‐Wen 
Published: August 2002

AbstractRigid poly(vinyl chloride) (PVC), PVC/chlorinated polyethylene (CPE), and PVC/CPE/oxidized polyethylene (OPE) compounds were prepared in a Haake torque rheometer. The fusion percolation thresholds (FPTs) of these compounds were defined and compared. Moreover, the fusion curves of these compounds were illustrated and compared. A higher processing temperature resulted in a shorter fusion time and a lower FPT. For PVC/CPE compounds, a higher concentration of CPE could decrease the FPT and promote PVC particles to fuse together easily. Meanwhile, in the beginning of the fusion process, the interaction between a higher concentration of OPE and calcium stearate in PVC/OPE compounds could also promote an easy fusion of the PVC particles. For PVC/CPE/OPE compounds, the synergistic interaction among CPE, OPE, and calcium stearate resulted in the shortest fusion time and the lowest FPT. The FPTs of rigid PVC samples were strongly dependent on not only the processing conditions but also the formulations of the samples. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3022–3029, 2001
Fabrication of 6FDA‐durene polyimide asymmetric hollow fibers for gas separation
Authors: Wang Rong , Cao Yiming , Vora Rohit , Tucker Robert J. 
Published: August 2002

AbstractWe have developed defect‐free asymmetric hexafluoro propane diandydride (6FDA) durene polyimide (6FDA‐durene) hollow fibers with a selectivity of 4.2 for O2/N2 and a permeance of 33.1 ×10−6 cm3 (STP)/cm2‐s‐cmHg for O2. These fibers were spun from a high viscosity in situ imidization dope consisting of 14.7% 6FDA‐durene in a NMP solvent and the inherent viscosities (IV) of this 6FDA‐durene polymer was 0.84 dL/g. Low IV dopes cannot produce defect‐free hollow fibers, indicating a 6FDA‐durene spinning dope with a viscosity in the region of chain entanglement seems to be essential to yield hollow fibers with minimum defects. The effects of spinning parameters such as shear rates within a spinneret and bore fluids as well as air gap on gas separation performance were investigated. Experimental data demonstrate that hollow fibers spun with NMP/H2O as the bore liquid have higher permeances and selectivities than those spun with glycerol as the bore liquid because the former has a relatively looser inner skin structure than the latter. In addition, the selectivity of hollow fibers spun with NMP/H2O as the bore liquid changes moderately with shear rate, while the selectivity of hollow fibers spun with glycerol are less sensitive to the change of shear rate. These distinct behaviors are mainly attributed to the different morphologies generated by different bore fluids. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2166–2173, 2001
Graft copolymerization ofN‐isopropylacrylamide on styrene‐butadiene‐styrene block copolymer
Authors: Lee Wen‐Fu , Chen Ying‐Jou 
Published: August 2002

AbstractGraft polymerization ofN‐isopropylacrylamide (NIPAAm) onto styrene‐butadiene‐styrene (SBS) block copolymer using benzoyl peroxide was studied to improve the water absorptivity and thermosensitivity of SBS. The influence of various grafting reaction factors on the conversion of NIPAAm and the grafting percentage of SBS‐g‐NIPAAm were also investigated in the study. The experimental results showed that the conversion of SBS‐g‐NIPAAm was enhanced as the monomers of NIPAAm were increased. The maximum conversion of SBS‐g‐NIPAAm was observed when the molar ratio of NIPAAm to butadiene was 1.25. In addition, increasing the reaction time enhanced the conversion of SBS‐g‐NIPAAm; the maximum grafting percentage was obtained with a 4‐h reaction. The optimal concentration of the initiator was 3 × 10−4mol/20 mL of toluene, and the grafting reaction occurred at over 65°C. The test results of the hydrophilicity of the grafted membranes showed that the hydrophilicity and thermosensitivity were significantly enhanced by grafting NIPAAm onto SBS. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2641–2650, 2001
Sorption, diffusion, and pervaporation separation of water–acetic acid mixtures through the blend membranes of sodium alginate and guar gum‐grafted‐polyacrylamide
Authors: Toti Udaya S. , Kariduraganavar Mahadevappa Y. , Soppimath Kumaresh S. , Aminabhavi Tejraj M. 
Published: August 2002

AbstractNonporous homogeneous dense membranes were prepared from the blends of sodium alginate (Na–Alg) with guar gum‐grafted polyacrylamide (GG‐g‐PAAm) in the ratios of 3 : 1 and 1 : 1 and these were tested for the pervaporation separation of water–acetic acid mixtures at 30°C. Blend compatibility was studied in solution by measuring the viscosity and the speed of sound. Membranes were crosslinked by glutaraldehyde. The GG‐g‐PAAm polymer and the crosslinked blend membranes were characterized by Fourier transform infrared spectra. High separation selectivity was exhibited by the pure Na–Alg membrane for water–acetic acid (HAc) mixtures containing 20 mass % of water. The permeation flux increased with increasing mass percent of water in the feed as well as with an increase in the amount of GG‐g‐PAAm in the blend, but separation selectivity decreased. Sorption selectivity was higher for the Na–Alg membrane than for the blend membranes, but it decreased with increasing mass percent of GG‐g‐PAAm in the blends. Diffusion selectivity values vary systematically with the blend composition, but not with the amount of water in the feed. Diffusion coefficients of the water–HAc mixtures were calculated from Fick's equation using sorption data and compared with those calculated from flux values obtained in pervaporation experiments. The Arrhenius activation parameters were calculated for the 20 mass % of water in the feed using flux and diffusion data obtained at 30, 40, and 50°C. The diffusion and pervaporation results are explained in terms of solution–diffusion concepts. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 259–272, 2002
Influence of casting substrate on the surface free energy of various polyesters
Authors: Smith R. , Pitrola R. 
Published: August 2002

AbstractThe surface free energies of various polyester surfaces have been determined from contact angle measurements using several liquid types. The geometric mean, the harmonic mean, and Fowkes' methods for obtaining the components of surface free energy have been compared for poly(L‐lactic acid) (PLLA), poly(DL‐lactic acid) (PDLLA), poly(hydroxybutyrate) (PHB), and poly(hydroxybutyrate‐hydroxyvalerate) (PHB–HV) copolymers. Polymer films were obtained by solution casting onto a number of smooth substrates, ranging from high‐energy surfaces (aluminum, mercury, glass, and freshly cleaved mica) to low‐energy surfaces [poly(ethyleneterephthalate) (PET), polytetrafluoroethylene (PTFE), and air]. Results show that the dispersion and polar surface free energy components of polyester surfaces cast against high surface energy (hydrophilic) substrates decrease with aging time toward a stable value. However, when cast against low surface energy substrates, the surface free energy of the resulting polymer/substrate‐contacting surface was independent of aging time. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 997–1008, 2002
The use of biomarkers in aquatic biomonitoring: the example of esterases
Authors: Pretti Carlo , Cognetti‐Varriale Anna Maria 
Published: August 2002

Abstract1. The term biomarker refers to the physiological, biochemical, and histological changes used as indicators of exposure to chemical contaminants and/or of its effects at the suborganismal or organismal level. Recently the development of sensitive biochemical markers for monitoring environmental quality in aquatic ecosystems has raised a great deal of interest.2. Selected biochemical markers measured in feral organisms can provide sensitive indexes, or early warning signals, of potential ecosystem degradation caused by contaminants. Compared with chemical residue analysis, biomarkers have the advantage of measuring the stress on the organism, thus being more biologically relevant.3. Some of the most frequently used biomarkers in aquatic biomonitoring in different countries are briefly described.4. The use of cholinesterase activity as a biomarker of pesticide exposure for biomonitoring in estuarine areas is also given as an example. Copyright © 2001 John Wiley & Sons, Ltd.