bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of negative photoreactive polyimide and its characterization
Authors: Li Zuobang , Zhu Pukun , Wang Lixin
Published: April 2003

In this article, a polyimide precursor was synthesized from oxydianiline and a diacid chloride. This diacid chloride was prepared by the reaction of thionyl chloride with a diacid, which resulted from the reaction of pyromellitic dianhydride with cinnamyl alcohol in N‐methylpyrrolidone (NMP). The photoresist, made from the above polyimide precursor, was spincoated onto silicon wafers, prebaked, and then exposed to UV light with a high pressure Hg lamp. The pattern generation process was also investigated. The appropriate conditions of the photolithographic procedures, involving photoresist compounding, spin coating, prebaking, exposure, development, rinse, postbaking, etc., were determined. The experimental results show that the photoresist exhibited excellent thermal stability and adequate photosensitivity.
Darzen's glycidic ester condensation reaction on poly(N‐vinyl pyrrolidone)
Authors: Devarajan R. , Arunachalam V. , Kumaraswamy M. D. K. , Tajuddin I. , Joghee T.
Published: April 2003

About 38% conversion of carbonyl groups into epoxy functions in the molecular chain of poly(N‐vinyl pyrrolidone) using chloracetamide results in the decreased viscosity of the product. De‐epoxidation of the epoxy groups introduced shows the most contributing factor towards decreased viscosity is epoxy function.
Preparation and properties of rigid polyurethane foams containing modified cornstarches
Authors: Cunningham R. L. , Carr M. E. , Bagley E. B.
Published: April 2003

Rigid polyurethane foams were prepared containing 20% (based on weight of polyol) unmodfied or modified cornstarches. The cornstarches had been modified by breeding or conversion methods and included waxy, acid‐modified waxy, malto‐dextrin, and canary dextrin. Due to its more favorable role as an extender, canary dextrin was added to additional foam formulations at 10–40%. Foams containing dextrins responded to compressive stress as control foams with yield points before 10% deformation. Foams filled with the unmodified or waxy cornstarches did not give clearly defined yield points and were measured at 10% deformation. After 14 days under 70°C and ambient conditions, volume increases for the filled foams were 4.0–7.1% vs. 4.6% for the control. The foams filled with canary dextrin increased in volume 4.3%. With the addition of 40% canary dextrin, the volume increases for the foams were 4.4% under thermal conditions and 4.5% under humid conditions (38°C and 98% relative humidity). Under humid conditions for 14 days, the foams containing canary dextrin increased in weight as dextrin content increased (1.5, 3.2, 3.4, and 7.6% with 10, 20, 30, and 40% dextrin, respectively). with 40% canary dextrin in the foams, thermal conductivity was 0.0235 vs. 0.0242 W/mK (0.163 vs. 0.168 Btu in/ft2h°F) for the control.
Chemical interaction between epoxidized natural rubber and silica: Studies on cure characteristics and low‐temperature dynamic mechanical properties
Authors: Varughese Susy , Tripathy D. K.
Published: April 2003

The unusual reinforcement mechanism exhibited by silica in epoxidized natural rubber (ENR) may be attributed to the specific chemical interaction or the chemical cross‐linking taking place between silica and the epoxy groups while heating the mix. Evidence for the higher interaction is established through rheometric studies conducted at 180°C and changes in the dynamic mechanical characteristics studied over a wide temperature range using a dynamic viscoelastometer for the heated and unheated silica‐filled mixes.
Effect of coupling agents on the mechanical properties of mica/epoxy and glass fiber/mica/epoxy composites
Authors: Bajaj P. , Jha N. K. , Kumar R. Ananda
Published: April 2003

The effect of coupling agents, two silane and one zirconate, on the mechanical properties of mica/epoxy and glass fiber/mica/epoxy composites has been investigated. The results showed that tensile modulus and flexural strength and modulus values were improved by the surface treatment of the coupling agents. The property retention was also found to be better in the case of coupling agent‐treated mica/epoxy samples after boiling in water for 2h. In the case of glass fiber/mica/epoxy composites, the flexural modulus and interlaminar shear strength values improved with increase in mica content, but the effect of coupling agents was not pronounced.
Pyrolysis kinetics of highly crosslinked polymethylsiloxane by TGA
Authors: Li Dong , Hwang Sun‐Tak
Published: April 2003

The pyrolysis kinetics of highly crosslinked polymethylsiloxane (PMS) was investigated by thermogravimetric analysis (TGA) under both isothermal and elevated temperature conditions with several environmental gases, such as oxygen, nitrogen, air, and helium. A non‐chain‐scission mechanism composed of initiation, propagation, and termination was proposed to interpret the thermal degradation of highly crosslinked PMS. The mechanism was verified by the experimental results under isothermal conditions. The activation energy of initiation, Ei, was about 20–30 kcal/mol and the activation energy of propagation, Ep, was about 4–6 kcal/mol. These activation energies were found to be different for different gases. The activation energy of initiation for PMS in an aggressive atmosphere, such as oxygen, was lower than that in an inert atmosphere, such as nitrogen. But the activation energy of propagation for PMS was higher in an active environment than in an inert one. There were no direct conclusions about the thermal degradation of highly crosslinked PMS at elevated temperature. Based on thermogravimetric experiments, it is suggested that a pyrolysis process be conducted with a rate of temperature increase less than 10°C/min for preparing the silicon base inorganic membrane.
Permeation and separation characteristics of alcohol–water mixtures through poly(dimethyl siloxane) membrane by pervaporation and evapomeation
Authors: Uragami Tadashi , Morikawa Takeshi
Published: April 2003

Permeation and separation characteristics for aqueous alcoholic solutions such as methanol/water, ethanol/water and 1‐propanol/water were studied using a poly(dimethyl siloxane) membrane by pervaporation and evapomeation. Poly(dimethyl siloxane) membrane preferentially permeated alcohol from aqueous alcoholic solutions in both methods. The concentration of alcohol in the permeate by evapomeation was higher than that by pervaporation. However, the permeation rate for the former method was smaller than that for the latter method. In evapomeation with a temperature difference between the feed solution and the membrane surroundings, when the temperature of the membrane surroundings was kept constant and the temperature of the feed solution was raised, both the permeation rate and the permselectivity for ethanol increased with increasing temperature of the feed solution. On the other hand, as the temperature of the feed solution was kept constant and the temperature of the membrane surroundings was changed, the permeation rate decreased, but the permselectivity for ethanol increased remarkably with dropping temperature in the membrane surrounding. Under permeation conditions of a feed solution of 40°C and a membrane surrounding temperature of −30°C in evapomeation, an aqueous solution of 10 wt % ethanol in the feed was concentrated to about 90 wt % in the permeate. The permselectivity for alcohol was in the order of methanol <ethanol <1‐propanol. The above permeation and separation characteristics are discussed from the viewpoint of the physicochemical properties of the poly(dimethyl siloxane) membrane and the permeating molecules.
Rheology of HTPB propellant. I. Effect of solid loading, oxidizer particle size, and aluminum content
Authors: Muthiah Rm. , Krishnamurthy V. N. , Gupta B. R.
Published: April 2003

Composite solid propellants based on hydroxyl‐terminated polybutadiene (HTPB) have become the workhorse propellants in the present‐day solid rocket motors. The other major ingredients of a composite propellant are the crystalline oxidizer and metallic fuel. As the solid loading of such propellants is as high as 86–90%, their rheological behavior is very complex. The propellant slurry needs to have reasonably low viscosity and a long pot life for better casting and, hence, for a defect‐free rocket motor. The primary factors affecting the solid propellant viscosity are solid content, particle size, shape, and distribution. The present study concerns the variations of solid loading from 80 to 89% at constant aluminum cotent, variation of aluminium from 0 to 22% at constant solid loading, and the coarse‐to‐fine ratio of the oxidizer. The plots of yield stress, consistency index, pseudoplasticity index, and thixotropic index at different time intervals are drawn for all these parametric changes. Based on these rheological studies, the optimum ratio of oxidizer coarse‐to‐fine ratio, aluminum content, and level of solid loading have been determined.
Damage evolution in flexible polyurethane foams
Authors: Kau C. , Huber L. , Hiltner A. , Baer E.
Published: April 2003

Microcrazing in the struts of flexible polyurethane foams was discovered during compressive deformation and observed directly in the scanning electron microscope. Attributed to this phenomena was the decrease in stress at maximum compression and the intensity of acoustic emission during compressive cycling. The higher content of styrene–acrylonitrile (SAN) copolymer in these foams resulted in higher modulus, more severe microcrazing, an increase in acoustic emission activity, and a decrease in the stress at maximum compression as cycling progressed.
Photoconductivity of poly((E,E)‐[6.2]paracyclophane‐1,5‐diene) and its complex with TCNE
Authors: Ulański J. , Kubacki J. , Głowacki I. , Kryszewski M. , Glatzhofer D. T.
Published: April 2003

Steady‐state photoconductivity measurements carried out for poly((E,E)‐[6.2]‐paracyclophane‐1,5‐diene) pure and sensitized with tetracyanoethylene show that doping causes a significant increase of the photoconductivity. This is due to an increase of both the hole mobility and the photogeneration efficiency. The shape of the spectral characteristic is explained by the possible existence of two paths for charge‐carrier photogeneration connected with absorption of the light by the cyclophane unit for shorter wavelengths or by CT complex for longer wavelengths. For an electric field lower than 106 V/m, the photocurrent exhibits an ohmic field dependence, and for higher fields, it becomes proportional to F1.5.
Swelling behavior of hyaluronic acid gels
Authors: Shah Chirag B. , Barnett Stanley M.
Published: April 2003

Hyaluronic acid is a naturally occurring mucopolysaccharide. It is an important component of the intercellular matrix. It controls the permeability of tissues by means of the highly entangled network which can be formed because of its high molecular weight. To be able to use hyaluronic acid for several biomedical applications it is necessary to have an understanding of its swelling properties. Equilibrium swelling properties of hyaluronic acid gels were investigated by varying the temperature, pH, ionic strength, and composition of the surrounding solution. Swelling was found to depend on pH and ionic strength and to be reversible. The gel was highly swollen at high pH, but it shrank continuously as the pH was lowered to 10% of its maximum volume. The gel was comparatively insensitive to temperature. Drying affected the swelling capacity of the gel significantly. Gel swelling was also affected by a high concentration of acetone or propyl alcohol in the aqueous swelling solutions.
Study of curative interactions in cis‐1,4‐polyisoprene (IR). VII. The cis‐1,4‐polyisoprene–tetramethylthiuram disulfide–ZnO system
Authors: Kruger F. W. H. , McGill W. J.
Published: April 2003

A detailed account of the mechanism of crosslinking in the cis‐1,4‐polyisoprene (IR)‐tetramethylthluram disulfide (TMTD)–ZnO system is given. Many experimental observations were harmonized in terms of a radical mechanism, rather than an ionic mechanism. Electron spin resonance (ESR) spectra on the IR–TMTD–ZnO system, recorded at 120°C, inter alia revealed resonance lines in the vicinity of g = 2.02. These were related to the rapid formation of thiuram persulphenyl radicals XS, on the homolytic splitting of tetramethylthiuram polysulfides. The Moore–Trego efficiency E dropped from 11.5 (at 140.0°C) to 3.5 (at 146.9°C), indicating that a substantial part of the sulfur atoms was initially to be associated with pendent groups. The formation of these pendent groups could be viewed as an irreversible, concerted reaction without the formation of a true alkenyl radical intermediate. Crosslinks would form by either a disproportionation reaction between two α‐methylic or α‐methylenic pendent groups RSxX or a reaction between a pendent groups RSxX (R = polyisoprenyl, x ≥ 2, X = Me2NC(S)) and the unsaturated polymer chain. The latter crosslink formation reactions were regarded as rate determining in the vulcanization sequence. A mechanism is proposed that does not require the participation of ZnO in the formation of the active sulfurating agent.
Coconut husk lignin. I. Extraction and characterization
Authors: Váquez‐Torres H. , Canché‐Escamilla G. , Cruz‐Ramos C. A.
Published: April 2003

Recently lignin has been the object of a renewed interest because of the need to use raw materials from renewable resources. One such resource is coconut husk, a material usually discarded during the copra extraction process. Due to its high lignin content, coconut husk has been recognized as having a variety of applications. Therefore, it is important to know the approximate structure of coconut husk lignin and those variations introduced by different isolation methods. This work reports a general characterization of coconut husk lignin. Results are given of the contents of hydroxyl and noncondensed guaiacyl units, the extractability of the lignin in alkaline and “organosolv” media along with thermal properties of the extracted lignins. The extraction system of NaOH–anthraquinone at 150°C was most conveniently based on the relatively low amount of condensed lignin generated.
The molecular weight distribution and oligomers of sodium hydroxide hydrolyzed poly(ethylene terephthalate)
Authors: Collins M. J. , Zeronian S. H.
Published: April 2003

Methanolic sodium hydroxide reacted more quickly than aqueous sodium hydroxide with poly(ethylene terephthalate) (PET). Larger amounts of low molecular weight deposits were formed at the product surface after the former treatment, also indicating the severity of this attack. The molecular weight distribution, obtained by gel permeation chromatography for the product of methanolic NaOH hydrolysis, had a population with 2400 peak molecular weight, which was not present on the chromatograph of the aqueous sodium hydroxide hydrolyzed product. This population is hypothesized to have been crystalline material. Extraction and analysis by high performance liquid chromatography of the low molecular weight products on the surface and in the bulk of the hydrolyzed PET samples, in comparison to controls, revealed the presence of more oligomeric species after hydrolysis. Also, more oligomeric species were present in the bulk extract of the methanolic sodium hydroxide hydrolyzed sample than in the aqueous NaOH hydrolyzed product.
On the mechanism of the formation of porous structure in filled polyethylene film by thermomechanical deformation
Authors: Islam M. A. , Dimov A.
Published: April 2003

The pore‐formation mechanism in filled polyethylene film during the process of thermomechanical deformation has been studied. The film material consists of a high density polyethylene and SiO2. The rate of deformation as well as the initial thickness of the polyethylene film play a vital role in the formation of the porous structure. With an increase in the deformation rate, the contribution of crazes in the film decreases. Keeping all the parameters constant, with the increase in the initial film thickness, the porosity of the membranes decreases. The mechanism of pore formation is observed by scanning electron microscopy. It is established that the formation of crazes in the deformation process starts from the zones with lower adhesion of the filler with polymer and in the course of the process propagates throughout the mass. The final pore‐size distributions as well as the permeability data provide additional indirect evidence in favor of the observed mechanism.
Structure formation in stretched sheets of poly(butylene terephthalate)
Authors: Kaito A. , Nakayama K. , Zubaidi
Published: April 2003

Crystalline and amorphous sheets of poly(butylene terephthalate) (PBT) were drawn in the temperature range of 20–150°C. The molecular orientation and the relative amount of α‐ and β‐form crystals in the stretched sheets were studied by wide‐angle X‐ray diffraction (WAXD) and density measurements. When crystalline PBT sheets are drawn at lower temperatures, α‐form crystals are partially transformed into β‐form crystals. Both α‐ and β‐form crystals are formed by drawing amorphous PBT sheets. The relative amount of α‐ and β‐form crystals is much more sensitive to drawing temperature than to draw ratio. The α‐form crystallinity is higher at higher drawing temperature and increases slightly with increasing draw ratio. The second moments of orientation functions of α‐ and β‐form crystals increase with increasing draw ratio, and the increase of the orientation function is suppressed at higher draw ratio. The orientation function of α‐form crystals is higher than that of β‐form crystals in a same sample.
Following of the relaxations in a polymer's behavior part I: “Correlation diagram” and creep at linearly increasing temperature
Authors: Genevaux J. M. , Guerrin G. M.
Published: April 2003

The correlation diagram is introduced here in order to follow the different relaxations of polymers. Two examples will be presented: PMMA and wood at several moisture contents between 20 and 100°C. For the two materials, an experiment of creep at linearly increasing temperature is proposed, so as to point out the relaxations of the different components for low frequencies. In this experiment, a relaxation induces a maximum of creep kinetic. The movement of the temperatures of relaxation with the moisture content will be observed. For wood at high moisture content (near the fiber saturation point), the cellulose's relaxation of the reinforcements will be observed at high temperature.
Physical aging deep in the glassy state of a fully cured polyimide
Authors: Venditti R. A. , Gillham J. K.
Published: April 2003

Physical aging of a fully cured polyimide/glass fiber specimen has been investigated deep in the glassy state using a freely oscillating torsion pendulum (TBA). A single specimen, the physical aging effects of which could be erased by heating to above Tg = 304°C (0.8 Hz), could be used for all experiments. Data were obtained during isothermal aging at different aging temperatures, Tα, (from 10°C to Tg) and during subsequent temperature scans (Tα to 5 to 315°C). The aging rate depended upon the value of Tα relative to both Tg and the β‐relaxation temperature, Tβ = 139°C (1.3 Hz). Changes in thermomechanical behavior due to aging were localized about Tα. This suggests that only an intermediate portion of the relaxation spectrum participates in, and is affected by, isothermal physical aging. It follows, and is observed, that the intensity of the β‐relaxation mechanical loss peak is perturbed most significantly by aging at Tα near Tβ. The effect of isothermal aging deep in the glassy state could be essentially eliminated by heating to below Tg. © 1992 John Wiley & Sons, Inc.
Synthesis of chiral polymers containing the acetoxybornyl group and their applications on the asymmetric induction
Authors: Liu Jui‐Hsiang , Kuo Jue‐Cheng , Fang Mau‐Ching
Published: April 2003

Optically active 2‐endo‐actoxy‐5‐endo‐bornyl methacrylate (ABMA) was prepared from (+)‐camphor. The homopolymerization of ABMA and copolymerization of ABMA with achiral methyl methacrylate (MMA) or styrene (St) were carried out with 2,2′‐azobisisobutyronitrile (AIBN) in benzene. Effects of temperature, solvents, and reaction time on the copolymerization were discussed. The monomer reactivity ratios(r1, r2) for poly(ABMA‐co‐MMA) and poly(ABMA‐co‐St) and Q and e values for the chiral ABMA in the copolymerization systems were evaluated by the Fineman—Ross method. The absolute value of the specific rotation of poly(ABMA‐co‐MMA) increased with increasing ABMA unit content. A small deviation from linearity was observed, which suggests that asymmetry is not introduced into the copolymer main chain. Temperature and solvent effects on the specific rotation of the chiral homopolymer and copolymers were investigated. The results suggest that the chiral polymers synthesized in this investigation did not show a strong preference for a particular helical conformation. Applications of the chiral polymers on the asymmetric addition of n‐butyllithium to aldehydes were also discussed.
Chlorination and bromination of epoxidized natural rubber (ENR)
Authors: Cataldo Franco
Published: April 2003

Epoxidized natural rubber (ENR) with a 25 mol % epoxide content has been chlorinated or brominated in halogenated solvents. The structures of the resulting polymers have been studied by infrared spectrophotometry, and their thermal behavior, by TGA and DSC, and compared with that of chlorinated and brominated natural rubber. For halogenated ENR, a structure of halogenated blocks separated by furanized blocks and products of ring‐opening epoxide groups has been proposed. © 1992 John Wiley & Sons, Inc.
Miscibility of polymethyl methacrylate with poly(hydroxy ether) of bisphenol A
Authors: Soh Young Soo
Published: April 2003

The miscibility of polymethyl methacrylate (PMMA) with the poly(hydroxy ether) of bisphenol A (phenoxy resin) was studied and PMMA has been found to be miscible with phenoxy resin. PMMA/phenoxy blends were found to be clear and showed a single, composition‐dependent glass transition temperature. The k parameter of the Gordon‐Taylor equation can be taken as a measure of the strength of the specific interaction between the two polymers, and a low value of k = 0.3 is found for the PMMA/Phenoxy blends. Fourier transform infrared (FTIR) showed the presence and nature of intermolecular interactions between the two polymers.
Shape memorizing properties of a hydrogel of poly(vinyl alcohol)
Authors: Hirai Toshihiro , Maruyama Hidetoshi , Suzuki Takashi , Hayashi Sadao
Published: April 2003

Hydrogel prepared by repetitive freezing and thawing of poly(vinyl alcohol) aqueous solution was chemically crosslinked with glutaraldehyde. The chemically crosslinked hydrogel hardly changed its physical appearance, and showed good elasticity and strength as original gel. However, after treating in boiling water, it swelled a little, depending on the condition of the chemical treatment. The melted gel thus obtained showed shape memorizing property, that is, it could firmly hold nearly 200% of strain, keeping its original high elasticity. The strain could be released very quickly (< 1 s) in boiling water, and the gel was suggested to be applied to a new type of gel actuator. X‐ray diffraction study revealed that the melted gel does not necessarily reform the physical crosslinks in exactly the same manner as the original gel in the process of shape restoring, but the distribution of the physical crosslinks can be restored as they were. It was suggested that the chemical crosslinks which remember the distribution of the physical crosslinks plays a critical roll in the shape restoring process.
Radiation‐induced sol–gel transition of protein: Effects of metal ions on flow and melting properties
Authors: Nisizawa Mizuho
Published: April 2003

Solid protein was irradiated with 60Co gamma rays, and the effects of metal ions (Cu2+ and Fe2+) on irradiated protein molecules were studied by measuring the viscosity of the protein hydrosol and the melting point of the protein hydrogel at different radiation doses and different concentrations of the metal ions. The effects of metal ions on the flow and thermal properties of irradiated protein molecules were discussed.
A mathematical model for a continuous esterification process with recycle between terephthalic acid and ethylene glycol
Authors: Yamada Toshiro
Published: April 2003

A new mathematical model for a continuous recycle esterification process has been derived by basically the same procedure as the continuous process of a cascade type, reported earlier, which includes material and heat balances. Such a model can give extensive information about the optimum design of a new plant through the predictions of oligomer characteristics (concentrations of carboxyl and hydroxyl end groups, number average molecular weight, number average degree of polymerization, esterification and saponification degree, DEG content, melting point of oligomer, etc.), distillate properties (concentrations of EG and water in the vapor phase), heat transfer area, mass flow rate of heating medium, amount of heat supplied by heating medium, enthalpy moving with recycle, and amount of heat removed from each reactor. © 1992 John Wiley & Sons, Inc.
The structure and morphology of the skin of polyethersulfone ultrafiltration membranes: A comparative atomic force microscope and scanning electron microscope study
Authors: Fritzsche A. K. , Arevalo A. R. , Connolly A. F. , Moore M. D. , Elings V. , Wu C. M.
Published: April 2003

Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) were used to investigate the surface structure and morphology of 10,000, 30,000, and 100,000 dalton molecular weight cutoff (MWCO) polyethersulfone (PES) ultrafiltration membranes, and the results are compared. Although both approaches reveal the pore structure in the 30,000 and 100,000 MWCO membranes, the pore diameters derived from SEM are smaller than those measured by AFM. This discrepancy is a result of the diminution in pore dimensions during the sample preparation for SEM, that is, the solvent exchange procedure needed to remove the water from the membrane prior to the high vacuum gold coating deposition step. In contrast to SEM, which requires a high vacuum both during heavy metal coating and during examination, AFM can be performed on wet ultrafiltration membranes. Consequently, the potential of altering the membranes' pore structures during sample preparation is eliminated. Therefore, the pore diameters obtained from AFM are more accurate than those derived from SEM.
Water‐superabsorbent polymers through gamma radiation‐induced graft‐copolymerization of acrylonitrile on guargum
Authors: Lokhande H. T. , Varadarajan P. V. , Iyer Vatsala
Published: April 2003

Superabsorbent polymers based on guargum have been prepared through a graft‐copolymerization reaction using acrylonitrile as the monomer by a gamma ray‐induced irradiation technique. Various grafting parameters have been studied. The grafted products have been characterized using infrared spectroscopy, thermogravimetric, and differential thermal analysis. The thermograms reveal the superior thermal stability of the grafted product over the control at all stages of its degradative cycle. The maximum absorbency obtained of the superabsorbent product was around 300 g/g.
Surface behavior of blends of siloxane and siloxane‐containing copolymers in poly(vinyl chloride)
Authors: Gorelova M. M. , Pertsin A. J. , Levin V. Yu. , Makarova L. I. , Filimonova L. V.
Published: April 2003

X‐ray photoelectron spectroscopy is used to reveal surface/bulk compositional relationships in blends of polydimethylsiloxane (PDMS) and PDMS/polycarbonate block copolymers in poly(vinyl chloride) (PVC). It is shown that the surface of PVC can be enriched in siloxane up to 60 at. % PDMS without visible indications of phase separation.
Separation of carbon dioxide by asymmetric hollow fiber membrane of cellulose triacetate
Authors: Sada E. , Kumazawa H. , Wang J.‐S. , Koizumi M.
Published: April 2003

Permeation behavior of pure CO2, O2, and N2 and separation characteristics of CO2–air mixtures were examined using hollow fiber modules of asymmetric cellulose triacetate membrane at 30°C. The ideal separation factor for CO2 relative to N2 ranged from 21 to 24. Permeation behavior for pure CO2 was interpreted in terms of the total immobilization model, i.e., a limiting case of the dual‐mode mobility model for glassy polymer, where the diffusion coefficient for Henry's law mode is not assumed to be constant and depends on gas pressure via a modified free‐volume model. Based on pure gas permeabilities to CO2, O2, and N2, simulation for the separation of CO2–air mixtures was made using a counter‐current plug flow model, and the result fitted the corresponding experimental data fairly well. Membrane plasticization induced by CO2 had negligible effect on permeation to mixture of CO2 and air in the range of CO2 composition up to 50% and upstream total pressure up to 1.5 MPa.
Aqueous dispersions of polyurethane anionomers: Effects of countercation
Authors: Chen Yun , Chen Yueh‐Liang
Published: April 2003

The influence of counterions on the properties of aqueous dispersions of polyurethane (PU) anionomer have been investigated. The PU anionomers were prepared by polyaddition reaction of 4,4′‐methylenebis(phenylisocyanate) with poly(propylene glycol) (PPG), dimethylolpropionic acid (DMPA), and 1,4‐butanediol, followed by neutralization of pendant COOH groups by various bases. Stable dispersions are obtained for PU anionomers containing 0.8–1.1 wt % COOH groups (17.8–24.4 mmol/100 g polymer) that have been neutralized by ammonia, trimethylamine, triethylamine, LiOH, NaOH, and KOH, respectively. It is found that average particle size is determined mainly by the zeta potential of the dispersions. The number‐average diameter of the dispersions containing metal cations (Li‐, Na‐, and K‐0.9) is between 60–73 nm (zetal potential −65 to −70 mV), while that of the dispersions containing ammonium cations (AMM‐, TMA‐, and TEA‐0.9) is between 104–251 nm (zeta potential −47 to −64 mV). The surface tension of the dispersions decreases with concentration rapidly and levels off at concentrations higher than 20 mmol/L. The decreased decomposition temperature of the PU anionomers, compared to unionized PUs, can be attributed to the disordering of hard domains after ionization or decomposition reaction catalyzed by alkali metal carboxylates. The thermal decomposition proceeds mainly via cyclic elimination.
Surface‐modified polysulfone hollow fibers. IV. Chloromethylated fibers and their derivatives
Authors: Higuchi Akon , Koga Hiroyuki , Nakagawa Tsutomu
Published: April 2003

A chloromethylated reaction was performed on the surfaces of polysulfone ultrafiltration hollow fibers and their derivative membranes, i.e., triethylaminated, ethylenediaminated, and acethylated fibers, were prepared. The modified fibers have a 30–60% insoluble region in chloroform, whereas nonmodified fibers can be dissolved in the chloroform. It is suggested that the insoluble parts of the fibers are highly cross‐linked due to the high degree of chloromethylation. The modified fibers showed a 50–98% rejection of polyethylene glycol 6000 at a feed concentration of 0.5 wt %, except for the triethylaminated fibers, which gave a negative rejection from −91 to −96%. It was found that the modified segments significantly influenced the rejection behavior of the solutes. Absorption of bovine serum albumin on the ethylenediaminated fibers at pH 7.1 was estimated from permeation measurements to be less than that of the other modified and nonmodified fibers. This effect is attributed to the hydrophilic surface of the ethylenediaminated fibers.
Poly(ethylene terephthalate) melt spinning via controlled threadline dynamics
Authors: Lin Chon‐Yie , Tucker Paul A. , Cuculo John A.
Published: April 2003

Fiber melt spinning of poly(ethylene terephthalate) (PET) was studied via modification of threadline dynamics. Several techniques were implemented in the high‐speed spinning process for the judicious control of threadline dynamics. This included a thermal conditioning zone (TCZ) for controlling the threadline temperature profile and a dydraulic drag bath (HDB) for controlling the threadline spinning stress. Through controlled threadline dynamics, key factors affecting the structure development—namely, temperature, tensile stress, and crystallization time—were manipulated to favor formation of a highly oriented and transversely uniform structure in the spun fibers. This carries the implication that optimum or near‐optimum processing conditions are being applied during the structure development period. More specifically, tensile stress in the threadline, independent of temperature, is substantially increased to many orders higher than that ordinarily attained in the normal high‐speed spinning process. Concurrently, the temperature crucial to the structure development is being independently optimized and its duration extended to attain a highly oriented structural order. Properties of the spun fibers were found to be correlated with the threadline parameters including cooling profile, tension profile, and strain rate. PET fibers spun via the one‐step process with the introduction of the TCZ and HDB possess superior mechanical performance. Structural characterization suggests that the spun fibers have a high amorphous orientation factor and a uniform radial structure distribution. Further on‐line studies indicate that structure development in the threadline is completely different from that of the traditional high‐speed spinning process. The attenuation profile of the threadline is observed to be dependent of TCZ temperature, residence time in the HDB, temperature of the HDB, and take‐up speed. It is believed that for the melt spinning process with the TCZ and the HDB, the threadline dynamics is changed from one controlled by inertia and air drag forces to one controlled by the imposed hydraulic drag.
The chemistry of Pd in cellulose acetate
Authors: Hwang Soon‐Taik , Shim Il‐Wun
Published: April 2003

Pd(OAc)2 complex has been incorporated in cellulose acetate (CA) as a dispersion medium using cosolvent (THF). The interactions Pd(II) complexes and cellulose acetate are examined by infrared spectroscopy and thermal analysis (DSC). The chemical reactivities of Pd–CA films have been investigated by reacting Pd sites with CO, H2, O2, and C2H4 in the temperature range 25–150°C and at the pressure of less than 1 atm. Two different Pd‐carbonyls and a Pd(O)‐hydride species formed in CA are characterized by their infrared spectra. Treatment of 10 wt % Pd–CA films with hydrogen (600 torr) at 70°C produces small Pd metal particles of ca. 30–60 Å in diameter in CA, which show catalytic activities under mild conditions in the reactions such as hydrogenation of C2H4 and oxidation of CO.
Percolation transition in heterogeneous ion exchange membranes
Authors: Šumberová V. , Bleha M. , Wodzki R.
Published: April 2003

Electrical conductivity and permeability for NaCl and glucose of heterogeneous cation and anion exchange membranes was studied as a function of the type of ion exchanger and swelling water content. Using membrane composition and the character of data obtained, it was proved that the percolation theory is suitable for the interpretation of experimental results. It was found for both the cationic and anionic type of membranes that the “insulator to conductor” and “nonpermeable to permeable material” percolation transition proceeds at a critical water fraction approximately 0.25. The exponent τ of the scaling equation is approximately 1.6, thus lying in the vicinity of the theoretical value for three‐dimensional systems.
Secondary relaxation, brittle–ductile transition temperature, and chain structure
Authors: Wu Souheng
Published: April 2003

We show that the subglass secondary relaxation temperature at which a polymer changes from brittle (crazing) to ductile (yielding) behavior is a function of the characteristic ratio C∞ (which is a measure of the intrinsic flexibility and rigidity of a coiled chain). At 1 Hz frequency, the correlation is given by {Tβ}/{Tα} = Tb/Tg = 0.135 + 0.082C∞, where {Tβ} is the secondary relaxation temperature, which corresponds to Tb the brittle—ductile transition temperature, and {Tα} is the primary relaxation temperature, which corresponds to the glass transition temperature Tg at the given frequency. The ratio {Tβ}/{Tα} or Tb/Tg can be predicted from chemical structure alone.
Synthetic resins. XX. Chelation ion exchange properties of resins derived from semicarbazone of 2‐hydroxy acetophenone‐substituted benzoic acid–formaldehyde
Authors: Bastia T. K. , Lenka S. , Nayak P. L.
Published: April 2003

A number of resins have been synthesized by reacting orthohydroxy acetophenone‐semicarbazone with substituted benzoic acid and formaldehyde in the presence of some acid and basic catalyst. The physicochemical properties of the resins have been reported. The ion exchange properties of the resins have been investigated. Influence of electrolytes on the metal uptake of Cu2+, Ni2+, Zn2+, Mg2+, and Mn2+ has been studied. The distribution of metal ions at different pH has also been reported. © 1992 John Wiley & Sons, Inc.
Measurement of the extent of reaction of an epoxy–cycloaliphatic amine system and influence of the extent of reaction on its dynamic and static mechanical properties
Authors: Jordan Catherine , Galy Jocelyne , Pascault Jean‐Pierre
Published: April 2003

An investigation was carried out into the effect of the extent of reaction on the mechanical properties, in a mixture of an epoxy prepolymer and a cycloaliphatic diamine, above the gel point. First, the most adequate technique to approach the extent of reaction was chosen between differential scanning calorimetry, Fourier transformation infrared, and size exclusion chromatography. It was found that the differential scanning calorimetry gave a good estimate of the extent of reaction, measuring the glass transition temperature and using a modified DiBenedetto equation. Dynamic mechanical properties and static mechanical properties are shown to be highly dependent upon the extent of reaction. The β relaxation was found to be responsible for the fracture properties at room temperature through the changes in extent of reaction. © 1992 John Wiley & Sons, Inc.
Removal of bacteria from water by systems based on insoluble polystyrene–polyethyelnimine
Authors: Tashiro Tatsuo
Published: April 2003

A study was made of the removal of viable bacterial cells from sterilized physiological saline (saline) by insoluble polymer beads. The polymers (CMPS–PEI300 and CMPS–PEI600) were prepared by reactions of chloromethylated, divinylbenzene crosslinked polystyrene (CMPS) beads with polyethyleneimines (PEI) (MW = about 300 and 600). The bacterial strain cells used were Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Pseudomonas aeruginosa (P. aeruginosa). Decrease coefficients (D, which corresponds to adsorption rate constant) for the viable cell numbers of E. coli by CPMS–PEI300 and CMPS–PEI600 were 28 and 120 (mL/gh) in saline, respectively. These D's were less than those (72 and 270 mL/gh) in sterilized, distilled, and deionized water (sterilized water). The D's for S. aureus and P. aeruginosa by CMPS–PEI600 were 46 and 76 (mL/g h), respectively. The D for E. coli by CMPS–PEI600 was compared with R (removal coefficient) for that by pyridinium type polymers. Bactericidal activity of PEI600 was examined on E. coli and P. aeruginosa in saline. Also, that of poly(ethylene glycol) 600 was done on E. coli in saline.
The adsorption of mercuric ions by chitosan
Authors: Peniche‐Covas C. , Alvarez L. W. , Argüelles‐Monal W.
Published: April 2003

The adsorption of mercuric ions by chitosan was investigated. The study of the adsorption kinetics shows that the rate of adsorption of mercuric ions on chitosan can be interpreted in terms of intraparticle diffusion as the rate‐limiting step. The experimental data of adsorption equilibrium from mercuric chloride solutions correlate well with the Langmuir isotherm equation, although at high‐solute concentrations, a multilayer type of adsorption with the subsequent increase in the uptake is observed. Column experiment confirms the ability of chitosan for the removal of mercuric ions from solutions in the absence of a high concentration of chlorides.
A new concentrated emulsion polymerization pathway
Authors: Ruckenstein E. , Sun F.
Published: April 2003

To ensure the stability of the concentrated emulsions that are employed as precursors for polymerization, a two‐step concentrated emulsion polymerization pathway is described. In the first step, the monomer is partially polymerized by heating at 50°C until a certain conversion is reached. Subsequently, the partially polymerized monomer is used as the dispersed phase to prepare a concentrated emulsion in which water constitutes the continuous phase. The concentrated emulsion has a large volume fraction of the dispersed phase (0.74–0.99) and the appearance of a gel. Several typical monomers are employed to correlate the stability of the concentrated emulsion and the extent of partial polymerization of the dispersed phase. It was found that monomers, which cannot lead to stable concentrated emulsions, can generate them after partial polymerization. Subsequent polymerization of the concentrated emulsion leads to latex particles. Copolymers and polymer composites were also prepared by the two‐step procedure. In the latter case, water was replaced with a solution of a hydrophilic monomer in water as the continuous phase. © 1992 John Wiley & Sons, Inc.
Thickness–direction thermal‐expansion measurements
Authors: Saraf Ravi F. , Tong Ho‐Ming , Poon Tze W. , Silverman B. David , Ho Paul S. , Rossi Angelo R.
Published: April 2003

Thermal expansivity in the thickness direction for three commercially synthesized and processed polyimide films, PMDA–ODA, BPDA–ODA, and BPDA–PDA, have been measured. The expansivity in the thickness direction is significantly higher than that in the in‐plane direction. The observed anisotropy is explained by the orientation texture of the films. The differences in the expansivity is explained by the molecular conformation of the chain. The latter is calculated by energy minimization excluding the entropic effects. The conformation analysis reveals a helical‐like conformation for ether‐linkage‐containing chains, which explains, which explains the higher expansivity in PMDA–ODA as opposed to BPDA–PDA. The possibility of helical conformation in PMDA–ODA and BPDA–ODA is novel. © 1992 John Wiley & Sons, Inc.
Effects of higher‐order structure of poly(3‐hydroxybutyrate) on its biodegradation. I. Effects of heat treatment on microbial degradation
Authors: Nishida Haruo , Tokiwa Yutaka
Published: April 2003

To clarify how the biodegradation of plastic is affected by physical properties based on the plastic's higher‐order structure, the microbial degradability of heat‐treated poly(3‐hydroxybutyrate) (PHB) samples was studied. Cast‐film samples and fibrous samples prepared with heat treatment were degraded by an isolated degrading bacterium: strain SC‐17. Consequently, it was found that the higher‐order structure properties such as crystallinity and modulus of elasticity of PHB acted as suppression factors. SEM observations of the degraded PHB films showed unique degradation patterns such as spherical and tubular holes on the surfaces and cells of SC‐17 in process of degrading the PHB surface. These patterns are thought to result from colonization of SC‐17 on the surfaces. From the results, it was suggested that the surface of the PHB was important as a growing field for the degrading bacterium and that the higher‐order structure properties of the PHB affected not only the degradation reaction but also the colonization of the degrading bacterium on the surface. © 1992 John Wiley & Sons, Inc.
Synthesis, characterization, and degradation of block polyesteramides containing poly(L‐lactide) segments
Authors: De Simone Vincenza , Maglio Giovanni , Palumbo Rosario , Scardi Vincenzo
Published: April 2003

Random multiblock polyesteramides (PEAs) having polyester (PE) content of 20–50 wt % have been prepared by low‐temperature polycondensation using sebacoyl chloride, 1,6‐diaminohexane, and telechelic oligomers of L‐lactide with Mn = 600–1500. The PEAs were characterized by IR and 1H‐NMR spectroscopy, wide‐angle X‐ray diffraction, and thermal analysis. Only the polyamide segments are able to crystallize, and the crystallinity depends on the composition and architecture of the PEAs. From viscosity and IR measurements it was established that the chain degradation of PEA powders or films suspended in buffer solutions occurs by hydrolysis of the ester linkages. The degradation rate is influenced by pH, PE content, and, to a lesser extent, by crystallinity. © 1992 John Wiley & Sons, Inc.
Structural changes of silk fibers induced by heat treatment
Authors: Tsukada Masuhiro , Freddi Giuliano , Nagura Masanobu , Ishikawa Hiroshi , Kasai Nobutami
Published: April 2003

The structural changes of silk fibers induced by heat treatment were investigated by thermomechanical analysis, dynamic mechanical measurements, X‐ray diffraction analysis, and refractive indices measurements. Bombyx mori silk fibers exhibited only a slight contraction, while tussah silk fibers showed a prominent two‐step contraction during the heating process. The dynamic storage modulus of B. mori fibers remained unchanged until the final decrease at about 170°C. The E' value of tussah fibers showed a slight increase ranging from 30 to 70°C and a final abrupt decrease at about 190°C. The broad peak of dynamic loss modulus showed a maximum at 220 and 230°C for B. mori and tussah silk fibers, respectively. The crystalline structure of silk fibers did not show any significant change regardless of heat treatment. The birefringence value of B. mori silk remained unchanged in the range from 25 to 240°C and then decreased, while that of tussah fibers decreased linearly. The isotropic refractive index increased for both silk fibers, even though with a different rate with increasing temperature. We proposed a schematic representation showing the structural changes of silk fibers induced by heat treatment, taking into account the changes in molecular orientation in the amorphous, laterally ordered and crystalline regions. © 1992 John Wiley & Sons, Inc.
Interactions of polymer model surfaces with cold plasmas: Hexatriacontane as a model molecule of high‐density polyethylene and octadecyl octadecanoate as a model of polyester. I. Degradation rate versus time and power
Authors: Clouet F. , Shi M. K.
Published: April 2003

To gain a better understanding of the evolution of polymer surfaces under cold plasmas, model polymer surfaces were studied. The degradation products and the gas phase were investigated by mass and optical emission spectrometry. Their evolution versus time and power enable us to propose a mechanism that involves atomic oxygen, OH* and H* radicals. © 1992 John Wiley & Sons, Inc.
Empirical prediction method of intrinsic light scattering loss of transparent amorphous polymers
Authors: Takezawa Yoshitaka , Taketani Noriaki , Tanno Seikichi , Ohara Shuichi
Published: April 2003

We studied simple empirical equations to estimate the values of intrinsic light scattering loss αR of various polymers applicable for plastic optical fibers, especially for aromatic amorphous polymers. The αR is divided into two losses, that is, αiso and αaniso. Here, αiso means the isotropic scattering loss; αaniso, the anisotropic scattering loss. The αiso is mainly a function of refractive index, and the αaniso is a function of refractive index, density, and the number of benzene rings in the polymer repeating unit. Therefore, when the polymer density and the structure of its repeating unit are known, the values of αR can be estimated. We derived new empirical equations for predicting the values of each intrinsic light scattering loss, αiso and αaniso. The estimated values were approximately equal to the experimental ones. The values of αR of aromatic amorphous polymers were not so large inherently, and they were a few hundred decibels per kilometer at the highest. © 1992 John Wiley & Sons, Inc.