bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology development of polymeric microparticles in aqueous dispersions. I. Thermodynamic considerations
Authors: Sundberg Donald C. , Casassa Anthony P. , Pantazopoulos John , Muscato Mark R. , Kronberg Bengt , Berg Johan 
Published: April 2003

AbstractA thermodynamic analysis of polymer particle morphology highlights the role of interfacial tensions in controlling particle structure. The influence of the surfactant and the nature of the incompatible polymers is seen through their individual and collective effects upon these interfacial tensions. It has been found that by simply changing the type of surfactant used in the emulsion the particle morphology can change from core‐shell to hemispherical, in agreement with thermodynamic predictions. Several apparently different morphologies (hemispherical, sandwich, multiple lobes) have been found to coexist at the same time within a single emulsion, suggesting that they may be simply different states of phase separation and not thermodynamically stable, unique morphologies. The thermodynamic analyses are independent of particle size and method of emulsion processing. Experimental evidence shows that the morphology of particles formed via in situ polymerization (as in a synthetic latex) is controlled by interfacial tensions in the same manner as those particles formed via solvent evaporation from a solution of an incompatible polymer pair (as in an artificial latex or microencapsulation).
Effects of surface cleaning and X‐ray irradiation in XPS study of polymers
Authors: Takahagi T. , Nakayama Y. , Soeda F. , Ishitani A. 
Published: April 2003

AbstractWe have examined effects of surface cleaning and X‐ray irradiation in XPS study of polymers. Contamination‐free surfaces of polymer samples for XPS study were successfully prepared by ultrasonic washing in organic solvents. Polymers were revealed to have lower surface chemical activity than metal and semiconductor crystals. The degradation behavior of polymers induced by X‐ray irradiation was found to be different from thermal degradation processes. Polymers like PET, polyimide, and PAN have high stability against X‐ray irradiation in XPS measurement. On the other hand, we must take degradation into consideration in XPS measurement for polymers such as PTFE and nylon because of their low stability against X‐ray irradiation. For an extremely X‐ray‐sensitive polymer like nitrocellulose, a quantitative XPS study cannot be carried out.
Effect of moisture sorption on ac properties of glass–epoxy composites
Authors: Doukkali K. , Segui Y. 
Published: April 2003

AbstractAlternating current responses of fiberglass‐reinforced epoxy composites have been studied as a function of frequency (10 Hz to 100 kHz) and temperature (−30 to 100°C). At higher water content, permanent defects are created presumably at the fiber—matrix interfaces as the temperature goes down to 0°C. These defects increase significantly the dielectric losses. A recovery of the initial state is possible under thermal annealing above the glass transition temperature of the epoxy resin.
The diffusion of oxygen through uniaxially and biaxially drawn polypropylene
Authors: Taraiya A. K. , Orchard G. A. J. , Ward I. M. 
Published: April 2003

AbstractThe oxygen permeability of uniaxially and biaxially drawn polypropylene has been studied for both film and tube samples. With few exceptions the permeability coefficient decreases on drawing, but effects are small, particularly for biaxially drawn material where the coefficient does not fall below about 60% of the isotropic value. Molecular orientation as indicated by refractive index measurements appears as a major cause of the reduction in permeability.
Numerical examination of the dual‐mode sorption model for sorption rate experiments with an extension for a mobile langmuir component
Authors: Riedl Carl M. , Spencer H. Garth 
Published: April 2003

AbstractNumerical methods were applied to the dual‐mode sorption model for sorption rate experiments with an immobilized Langmuir component over broad ranges of polymer characteristics and experimental conditions. The variation of the diffusion coefficient evaluated using a single scaling procedure was examined. The numerical procedure was also applied to the model for infinite volume sorption and to sorption allowing for mobility of the Langmuir component of the penetrant.
Synthesis and physical properties of poly(fluoroalkylether)urethanes
Authors: Yu X‐H. , Okkema A. Z. , Cooper S. L. 
Published: April 2003

AbstractPolyurethane block copolymers were synthesized containing between 33 and 50 wt % hard segments based on 4,4'‐diphenylmethane diissocyanate (MDI) and either 1,4‐butanediol (BD), or N‐methyldiethanolamine (MDEA) as the chain extender. The soft segments were composed of poly(tetramethylene oxide) (PTMO) and fluoropolyether glycol (FPEG) oligomers (Mn = 1000 and 1899, respectively), copolymerized to produce polyurethanes containing 5–100 wt % FPEG soft segment. The PTMO polyol in one sample was substituted with a tetrahydrofuran/ethylene oxide polyol (75 : 25 mole ratio) (Mn = 1140). The MDEA‐extended polymer was ionized using 1,3‐propane sultone. The bulk and surface properties of these polymers were evaluated by a variety of techniques. Differential scanning calorimetry (DSC) and dynamic mechanical analysis showed that the incorporation of 5–14 wt % FPEG into the soft segment had essentially no effect on the polymer's multiphase structure. The ultimate tensile strength and elongation was reduced by the addition of FPEG. Chain extending with BD as opposed to MDEA improved phase separation and the ultimate tensile strength. In vacuum, surface enrichment of the low surface energy FPEG was observed for all the polymers, using X‐ray photoelectron spectroscopy (XPS). The dynamic contact angle results indicate that the polymer surfaces rearranged in an aqueous environment to minimize their interfacial free energy.
Structure—property relationships of polyurethane ionomers with star chain architecture
Authors: Thompson Patrick A. , Yu Xuehai , Cooper Stuart L. 
Published: April 2003

AbstractThe effects of chain architecture, polyol chemistry and polyol molecular weight on the properties of elastomeric polyurethane ionomers were investigated. The type of polyol and its molecular weight had a strong influence on the rubbery modulus and tensile properties. Variations in chain architecture showed little impact on mechanical and thermal properties. Linear ionomers, threearm ionomers, and six‐arm ionomers had similar mechanical and thermal behavior.
Preparation and cationic electrodeposition of amine—functional epoxy resins
Authors: Yang Chin‐Ping , Lee Lung‐Ta 
Published: April 2003

Abstract2‐Ethylhexanol‐blocked toluene diisocyanate (2‐EH‐blocked TDI) modified resin was first prepared from epoxy resin and 2‐EH partially blocked TDI and subsequently reacted with di(2‐methylisobutylketiminoethyl)amine to obtain ketimine‐terminated resins. These ketimine‐terminated resins were hydrolyzed and partially neutralized with acetic acid to give macrocations. The resulting cationic resins were dissolved in suitable solvents and mixed with deionized water to form various emulsions. The formation of a stable emulsion is strongly dependent on the pH value of the emulsion and the amount of solvent added. Electrodeposition of the emulsion produced films of amine‐terminated and 2‐EH‐blocked TDI modified epoxy resins on the surface of a cathode. Factors such as the pH value of the emulsion, the content of organic solvents, the amount of 2‐EH‐blocked TDI, applied voltage, and electrodeposition time on the electrodeposition properties (such as deposition yield and throwing power of the resins) were investigated. Moreover, the deposited film could be thermally cured to have a crosslinked structure. It was found that a temperature above 160°C is required to crosslink the deposited resins.
Studies on flame retardancy of polyacrylonitrile fiber treated by flame‐retardant monomers in cold plasma
Authors: Akovali G. , Gundogan G. 
Published: April 2003

AbstractPlasma polymer hexamethyldisiloxane, ethyldichlorophosphate and tris(butoxyethyl)phosphate modified polyacrylonitrile fibers were examined by FTIR, XRF, and SEM and the extend of flame retardancy introduced were checked. Certain levels of concentrations of flame‐retardant elements grafted or coated at the fiber surface during plasma treatment are believed to overcome some negative effects of a number of reactions that usually are concurrent with plasma polymerization, such as crosslinking.
Optical anisotropy of polyimide
Authors: Nakagawa Koichi 
Published: April 2003

AbstractOptical anisotropy of polyimide films prepared from polyamic acid solutions was investigated by conoscopic observation and refractive index measurements. The conoscopic figure (crossed pattern) characteristic of a negative uniaxial crystal with its optic axis perpendicular to the film plane was observed for samples imidized on substrates. Uniaxial drawing of a polyamic acid cast film with 40 wt % solvent gave a highly oriented sample with an elongation of more than 80%. This sample had a conoscopic figure characteristic of a positive uniaxial crystal with its optic axis equivalent to the molecular c axis (parallel to the film plane). A large optical anisotropy (bire‐fringence 0.18) was observed in the film plane. The TE‐mode refractive index (parallel to the film plane) ranged from 1.64 to 1.82 at a wavelength of 633 nm according to the sample rotation. These values corresponded to the refractive indices perpendicular and parallel to the c axis, respectively. The optical system change of the polyimide film was explained in terms of the uniaxial orientation of the in‐plane oriented molecular c axis.
Pervaporation separation of ethanol–water mixtures using crosslinked blended polyacrylic acid (PAA)–nylon 66 membranes
Authors: Zhao X. P. , Huang R. Y. M. 
Published: April 2003

AbstractThe pervaporation separation of ethanol–water mixtures was carried out through a series of ionically crosslinked polyacrylic acid (PAA)–nylon 66 blended membranes crosslinked to varying degrees in aluminum nitrate solution. Optimum pervaporation results were obtained from crosslinked blends containing 75 wt % nylon 66 and 25 wt % PAA. The optimum crosslinking time was found to be between 30 and 40 h. The optimum operating temperatures of the pervaporation runs were found to be 2–3°C below the boiling points when the highest permeation flux reached 857.6 (g/m2 h) and the best separation factors (water/ethanol) were 10.1.
Kinetic effects on the impurities in epoxy‐resin/m‐xylylenediamine reaction
Authors: Abuín Senén Paz , Pellín Mercedes Pazos , Núñez Lisardo 
Published: April 2003

AbstractDifferent isolated or competitive mechanisms have been experimentally observed in order to predict the kinetics of an epoxy—amine reaction in terms of various mathematical models based on different possibilities of reaction. Impurities such as water, glycols, and in general all donors of active hydrogen even at low concentrations significantly change the course of the reaction. We therefore decided to study the curing reaction of the epoxy resin, first as a commercial product and later purified, with m‐xylylenediamine of known purity. The extent of cure has been followed and determined by differential scanning calorimetry (DSC) and infrared spectroscopy (FT‐IR). Purity, epoxy content and OH content were measured by liquid chromatography HPLC and wet analysis.
Study of critical phenomena of polystyrene—poly(vinyl methyl ether) blends by solid state NMR
Authors: Chu C. W. , Dickinson L. C. , Chien James C. W. 
Published: April 2003

AbstractThermally induced phase separation in PS/PVME blends was studied by solid state NMR. The proton spin—lattice relaxation in both the laboratory and the rotating frame were measured for the entire range of blend composition. Under conditions in which the blends are said to be compatible by other techniques T results obtained at −5°C showed microheterogeneity at a 10−°A scale. T1pH values at room temperature are closer to the longer relaxation time of PS than that expected from simple weighted average of the relaxation times of the constituent homopolymers. This indicates incomplete averaging by spin diffusion and a restraining effect of PS on segmental motions of PVME. The blends were heated to cause phase separation and quenched. From the biphasic decay of 13C magnetization, the compositions of the separated phases were estimated to give a lower critical solution temperature phase diagram. NMR relaxation in PVME blends with PS molecular weights of 9, 100, and 900 K were compared.
Transport of a gas through asymmetric polysulfone membranes with deposited plasma‐polymerized thin layer
Authors: Sada E. , Kumazawa H. , Xu P. , Inoue H. 
Published: April 2003

AbstractA plasma‐polymerized thin layer was deposited on the top surface of the skin layer of the asymmetric polysulfone (PSF) membrane to plug ultrafine pores passing through it. Trifluoromethane was used as the monomer gas of plasma polymerization. The steady‐state permeation rates for oxygen and nitrogen through the asymmetric PSF membranes with the plasma modification were measured to evaluate the permselectivity and permeability. If ultrafine pores passing through the asymmetric membrane can be plugged by the plasma‐polymerized thin layer, the separation factor of oxygen relative to nitrogen can be increased with the permeation rate coefficient of oxygen still kept large. This condition was met when the vaporization time of the cast solution during the preparation of an asymmetric membrane ranged from 10 to 120 s and the plasma polymerization time ranged from 15 to 30 min.
Crosslinking of an epoxy with a mixed amine as a function of stoichiometry. II. Final properties via dynamic mechanical spectroscopy
Authors: Wingard Charles D. , Beatty Charles L. 
Published: April 2003

AbstractVariation of the epoxy/curing agent ratio for a system containing a diglycidyl ether of bisphenol‐A (DGEBA) and a mixed aromatic amine was found to have a significant effect on the cure kinetics and final dynamic mechanical properties of both the neat resin and glass reinforced epoxy. For a partial B‐stage cure to an ultimate C‐stage cure, optimum cure temperatures were obtained as a function of stoichiometry. For the ultimately cured (C‐stage) resin, the molecular weight between crosslinks (Mc) passed through a minimum, and both the glass transition temperature (Tg) and a secondary (sub‐Tg) transition passed through a maximum at the stoichiometric ratio. In addition, the activation energy of the ultimately cured resin passed through a maximum at or near the stoichiometric ratio for both the Tg and sub‐Tg transitions.
Study on tribochemical interaction of metals or metal oxides with polytetrafluoroethylene by X‐ray photoelectron spectroscopy
Authors: Gong De‐Li , Zhang Bing , Xue Quin‐Ji , Wang Hong‐Li 
Published: April 2003

AbstractTribochemical reactions of PTFE with aluminum, silicon, and iron during rubbing were detected by ESCA. No apparent relationship between this chemical reaction of the fillers with the PTFE in the composite and the wear‐reducing action of those fillers on the composite material was found.
Effects of temperature and catalyst level on the cure rate of fiber‐reinforced plastic (FRP)
Authors: Ozokwelu Enuma Dickson 
Published: April 2003

AbstractIn order to allow manufacturers of fiber‐reinforced plastic (FRP) products to determine an optimum catalyst level for their application, an investigation was made of the effects of ambient temperature and catalyst level on the gel time of polyester resins. Gel times were determined using standards set by the Society of the Plastics Industries, Inc.5 The gel times thus obtained compared favorably with published gel times for general purpose polyester resins. It will be left to the individual manufacturer to determine the optimum catalyst level for his or her application, as very short gel times will cause the resin to harden too quickly to allow fabrication of large parts. In general, the optimum catalyst level is defined as that which produces the shortest usable gel time.
Physical characterization of incompatible blends of polymethylmethacrylate and polycaprolactone
Authors: Iannace S. , De Luca N. , Nicolais L. , Carfagna C. , Huang S. J. 
Published: April 2003

AbstractBlends of polymethylmethacrylate (PMMA) and poly‐ε‐caprolactone (PCL) were prepared and characterized. The analysis of the glass transition temperature indicates no compatibility of the two polymers, which segregated into two distinct phases. The fracture strength of the blends can be explained on the basis of a constitutive model of spheres of PCL embedded in a PMMA matrix. The trend of water sorption confirms the hypothesis of phase segregation of PCL in the glassy matrix of PMMA.
Synthesis and evaluation of methyl methacrylate copolymers and terpolymers as electron‐beam resists. I. Poly(methyl methacrylate–methacrylic acid–methacryloyl chloride)
Authors: Gitsov Ivan , Madjarova Nikolina A. 
Published: April 2003

AbstractTerpolymers of methyl methacrylate with methacrylic acid and methacryloyl chloride [poly(MMA‐MAA‐MAC)] were synthesized with high yields by slow radical polymerization. The influence of the temperature of prebaking on the changes in the chemical composition and the molecular weight characteristics of poly(MMA‐5%MAA‐5%MAC) was studied by infrared spectroscopy and gel permeation chromatography. It was found that resists containing terpolymer with molecular weight (M̄w) of 41,000, which were prebaked at 100°C, were able to produce high contrast images (γ = 3.3) at doses of 16 μC/cm2.
Improvement of wood properties by impregnation with multifunctional monomers
Authors: Mathias Lon J. , Lee Soo , Wright John R. , Warren Stephen C. 
Published: April 2003

AbstractSouthern pine samples with different dimensions and bulk densities were impregnated with the multifunctional monomer ethyl α‐hydroxymethylacrylate (EHMA) and 5 mol % of fluorinated or nonfluorinated crosslinking agent. The maximum impregnation yield (105% by weight) was achieved under vacuum with good improvement of water repellency.Impregnation with EHMA plus another multifunctional monomer 2‐vinyl‐4,4‐dimethyl‐2‐oxazolin‐5‐one (vinyl azlactone) was carried out to improve the mechanical properties of wood samples. Water repellency was also improved depending on the amount of vinyl azlactone in the monomer solution. A maximum of 41% antiswell efficiency (ASE) was obtained by impregnation with a 9 : 1 w/w mixture of EHMA and vinyl azlactone. Improvements of 38–54% in impact strength and 27–44% in compression modulus were achieved depending on the relative amount of vinyl azlactone incorporated. FT‐IR and solution or solid‐state NMR spectroscopy were used for chemical characterization of the polymers themselves and the wood‐polymer composites.
Highly fluorinated epoxy resin. II. Behavior in blend applications
Authors: Twardowski T. E. , Geil P. H. 
Published: April 2003

AbstractThe behavior of a highly fluorinated epoxy resin blended with Epon 828 was studied. The two resins are immiscible, resulting in 10–20‐μm spherical domains and a surface layer of fluorinated resin. A B stage for the blend providing for good ply lamination is indicated. The mechanical properties of the blend were commensurate with the Epon phase.
Modeling the bulk polymerization of methyl methacrylate with glycol dimercapto acetate as chain transfer agent
Authors: Destruel P. , Taufer M. , Granel C. 
Published: April 2003

AbstractThis paper investigates the bulk polymerization of methyl methacrylate (MMA) when chain transfer to a low‐molecular‐weight agent is important. A transfer rate constant and a transfer efficiency are introduced into the equations. Calculations of the kinetics of polymerization and of the weight‐average molecular weight distribution are in good agreement with experimental results.
Solubility parameters of polymethacrylonitrile, poly(methacrylic acid) and methacrylonitrile/methacrylic acid copolymer
Authors: Ho Bang‐Chein , Chin Wei‐Kuo , Lee Yu‐Der 
Published: April 2003

AbstractThe solubility behaviors of polymethyacrylonitrile (PMAN), poly(methacrylic acid) (PMAA), and its random copolymer methacrylonitrile (MAN)/methacrylic acid (MAA) in various solvents were investigated. The results were used in a computer program to obtain a 3‐dimensional representation of the polymer solubility region in the Hansen space. Thus, the values of dispersion (δd,p), polar (δp,p) and hydrogen bonding (δh,p) components of the total solubility parameter (δt,p) were obtained. Comparisons between the experimental results and the estimated values are discussed. Also, prediction for solubility parameter values for MAN/MAA copolymer via their homopolymers, PMAN, and PMAA has been evaluated.
Lifetime prediction of carboxyl‐terminated polybutadiene (CTPB)
Authors: Bilgin Ferda , Sage Tubitak , Orbey Nese , Guven Olgun 
Published: April 2003

AbstractCarboxyl‐terminated polybutadiene (CTPB) was subjected to temperature and humidity aging in order to estimate its useful lifetime as a solid propellant binder. CTPB samples were temperature aged from 1 week to 7 months at various temperatures ranging from 50 to 100°C. At various stages of temperature aging, viscosity of the samples were measured, end group analyses were performed, and the samples, after being crosslinked with MAPO, were mechanically tested. As far as mechanical properties are concerned, the ultimate tensile stress of the samples decreases with temperature aging and strain at break increases. End group analyses indicate that acid value of the samples decreases with aging and viscosity increases. The results of temperature aging were applied to an Arrhenius type time‐temperature superposition relation and useful lifetime of CTPB as binder at 20°C was predicted to be around 10 years. The CTPB samples were also humidity‐aged and the effects of humidity aging on mechanical properties were investigated. The results indicate that similar to temperature aging, ultimate tensile strength decreases and strain at break increases with aging. The effects of humidity aging, however, is much less pronounced in comparison to temperature aging.
Radiation curable, micelle forming, block copolymers as soil release finishes for polyester fabrics
Authors: Warburton C. E. 
Published: April 2003

AbstractPolyester fabrics were treated with aqueous solutions of block copolymers prepared from a polyethylene oxide diol, a diisocyanate, and 2‐hydroxyethyl acrylate. The copolymers formed micelles in aqueous solution. Electron beam irradiation in the wet state produced fabrics with much improved release of oily soil on laundering.
A comparative study on polymers containing different ultraviolet stabilizer moieties
Authors: Pasch H. , Shuhaibar K. F. , Attari S. 
Published: April 2003

AbstractA number of styrene and methylmethacrylate copolymers containing different UV stabilizer units (benzophenone, phenylbenzotriazole, and naphthylbenzotriazole) fixed to the polymer backbone were characterized by UV spectroscopy and size exclusion chromatography. UV spectroscopy was found to be suitable for the determination of the copolymer composition and the stability of intramolecular hydrogen bonds, which are important for the performance of UV stabilizer molecules. The highest stability of the intramolecular hydrogen bond was obtained for phenylbenzotriazole containing polymers. Using size exclusion chromatography with refractive index and ultraviolet detection, it was shown that the UV stabilizer units were statistically distributed along the different molar mass fractions.