bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of plasma gas species on the adhesion of thermoplastic to organic fibers
Authors: Pitt William G. , Lakenan John E. , Brent Strong A. 
Published: April 2003

AbstractAdhesion between organic fibers and thermoplastics in a composite material is usually weak because of the lack of chemical and mechanical bonding. This study investigated the influence of plasma gas species in a novel technique to improve interfacial adhesion of Kevlar 49 fibers to polycarbonate. Single Kevlar fibers were exposed to radio‐frequency plasma discharge in atmospheres of argon, oxygen, and ammonia. Plasma treatment has been shown to generate reactive free radicals on polymer surfaces. The fibers that were coated immediately with a polycarbonate melt while still in the vacuum environment of a plasma reactor showed an increase in interfacial shear strength that was maximum at 4.1 s exposure and decreased at longer exposure times. At 4.1 s exposure, Ar and O2 plasma treatment increased shear strength by 20 and 18%, respectively. NH3 plasma treatment produced only a statistically insignificant increase at 4.1 s of exposure and a significant decrease in adhesion at 8.3 s of exposure. Fibers that were exposed to air for 1 h before coating showed no statistically significant increase or decrease in adhesion. The increase in adhesion of the directly coated fibers was attributed to free radical‐initiated formation of covalent bonds between the Kevlar and the polycarbonate. © 1993 John Wiley & Sons, Inc.
Dynamic mechanical properties of silica‐filled ethylene vinyl acetate rubber
Authors: Mukhopadhyay K. , Tripathy D. K. , De S. K. 
Published: April 2003

AbstractDynamic mechanical studies of ethylene vinyl acetate rubber indicated the presence of different transitions: the α‐transition or glass‐rubber transition temperature (Tg) at −17°C, the γ‐transition around −60 to −70°C observed as a shoulder, and the γ‐transition in the temperature region of −127 to −135°C, apart from a high‐temperature transition (T1,1) at +69°C. The α‐transition temperature did not shift its position with incorporation of silica filler, but there was gradual sequential lowering of tan δ peak values at Tg with increase in filler loading. Such sequential dependence of tan δ values on filler incorporation was not observed in the cases of β‐ and γ‐transitions. The T1,1 transition was found to be less prominent in the presence of filler, particularly at high concentration. Treatment of the filler with a silane coupling agent caused a shift in the α‐transition temperature to higher temperature by about 4°C. Studies on dynamic mechanical properties under isothermal conditions have shown that the coupling agent caused a breakdown of silica agglomerates during mixing. An increase in frequency caused a shift of tan δ peak positions in the α‐ and γ‐transition regions toward higher temperature. Although frequency did not have a significant effect on the tan δ value at the α‐transition, increase in frequency caused sequential lowering of tan δ value at the α‐transition. increase in frequency caused sequential lowering of tan δ value at the γ‐transition. In the high‐temperature region, the T1,1 peak exhibited by the gum compound gradully disappeared with increasing frequency. © 1993 John Wiley & Sons, Inc.
Relationship between cellulase treatment and the dyeability with a direct dye for various kinds of cellulosic fibers
Authors: Mori Reiko , Huga Toshio , Takagishi Toru 
Published: April 2003

AbstractThe cellulosic fibers were dyed to equilibrium with Congo Red before and after cellulase treatment. The fibers examined were rayon, polynozic, cupra, flax, and cotton. It was found that the volume term for dyeing (V) was associated with weight loss (WL) caused by the cellulase treatment, for the original fibers. Apparent affinity for dyeing (AF) for the cellulase‐treated fibers was calculated using a constant value of V obtained for each kind of the original fibers. The results led to the assumption that there would be two kinds of the regions that could be accessible to dye. One would be the region that was readily digested by the enzymatic hydrolysis. The other would be the region that was additionally developed by the attack of cellulase. The previously dyed fibers were hydrolyzed by cellulase. It was found that the physical bondings that formed between cellulose and Congo Red molecules would block the hydrolysis by cellulase for all the fibers examined. It was also assumed that there would be a region that could be accessible to cellulase but not entirely to Congo Red. © 1993 John Wiley & Sons, Inc.
Universal calibration assessment in aqueous gel permeation chromatography
Authors: Bahary W. S. , Jilani M. 
Published: April 2003

AbstractIt was the objective of this paper to assess the applicability of the universal calibration method to aqueous GPC/SEC with nonionic and anionic polymers using the Viscotek differential viscosity detector. Three water‐soluble polymers—polyacrylic acid, dextran, and polyethylene oxide—were chromatographed using four UltrahydrogelTM columns with 0.3 M NaCl and 0.1M KH2PO4 as the mobile phase adjusted to pH 7. Three distinct calibration curves were obtained. Upon addition of 10% methanol, a reasonably good universal calibration curve was obtained. However, quantitative analysis of the data exhibited about 5% deviation in average Mw and Mn for sodium polyacrylate as calculated from the single curve as opposed to about 40% when calculated from the composite curve. The applicability of three theoretical models for the universal calibration method was assessed, and a recommendation was made for future work. © 1993 John Wiley & Sons, Inc.
Studies on compatibilization of blends of polypropylene and a thermotropic liquid crystalline polymer
Authors: Heino Markku T. , Seppälä Jukka V. 
Published: April 2003

AbstractThermotropic liquid crystalline polymers, LCPs, are frequently blended with thermoplastics to achieve an in situ composite structure. Significant mechanical reinforcement is obtained for the matrix polymer in the direction of the LCP fibers, but the transversal properties are often inferior because of the incompatibility of the components. Blends of LCP with polypropylene, and with three related matrix polymers, and PP/LCP blends with added potential compatibilizers were prepared and studied for their mechanical properties and morphology. A notable improvement in impact strength was achieved when a small amount of ethylene‐based terpolymer was added as compatibilizer. © 1993 John Wiley & Sons, Inc.
Surface modification of polyethylene by remote dc discharge plasma treatment
Authors: Behnisch J. , Holländer A. , Zimmermann H. 
Published: April 2003

AbstractThe surface modification of polyethylene in a remote nitrogen, oxygen, and hydrogen dc discharge plasma was investigated. In the case of the nitrogen plasma a strong correlation exists between the concentration of active nitrogen species, as detected by Langmuir probe measurements and plasma emission spectroscopy, and the time dependence of the polymer surface modification, as detected by contact‐angle measurements. The obtained contact‐angle data were interpreted in terms of the acid–base model for the interaction of the test liquid with the polymer surface. There was a great similarity in the functionalization of the polyethylene surfaces treated with nitrogen as well as with oxygen plasma, except in the intial stage, where in the former, mainly functional groups acting as electron acceptors were formed, whereas in the latter a sharp increase in the content of both electron donor as well as electron acceptor groups was detected. Thus, a determining influence of oxygen residues in the remote nitrogen plasma was indicated. The absence of such an effect in the case of the hydrogen plasma could result from direct quenching of reactive oxygen species and / or the chemical reduction of formed oxygen containing functionalities by hydrogen species. © 1993 John Wiley & Sons, Inc.
Fibers from a soluble, fluorinated polyimide
Authors: Dorogy William E. , Clair Anne K. St. 
Published: April 2003

AbstractPolyimide fibers have been produced from both polyamic acid and polyimide resins, derived from 2, 2‐bis (3,4‐dicarboxyphenyl) hexafluoropropane dianhydride and 2, 2‐bis (4‐4‐aminophenoxy) phenyl) hexafluoropropane, by extrusion into various aqueous organic media. Polyimide fibers obtained from polyamic acid fibers after thermal imidization exhibited round or oval cross‐sections, while fibers obtained directly from a polyimide resin had dogbone, C‐shaped, or oval cross‐sections. The effect of polymer inherent viscosity and filament production parameters on the formation of macropores within the filament will be discussed. Tensile properties of fibers, produced under various conditions, are listed and compared. © 1993 John Wiley & Sons, Inc.
Effects of compatibilization on fractionated crystallization of PA6/PP blends
Authors: Ikkala O. T. , Holsti‐Miettinen R. M. , Seppälä J. 
Published: April 2003

AbstractIn polymer blends, the crystallization of the dispersed semicrystalline component depends on the type and distribution of the nucleating heterogeneities and on the level of the dispersion. Either fractionated or coincident crystallization may result. In this study, the effect of compatibilizers on the crystallization of polyamide 6/isotactic polypropylene (PP) blends was investigated. The morphology was controlled with 10 wt % of four different commercial compatibilizers—PPgMAH, EBAgFA, SEBSgMAH, and E‐EA‐GMA—each leading to specific morphology and crystallization behavior. The compatibilized blends show more complex crystallization compared with the corresponding binary blends. In the compatibilized blends, the dispersed PA6 seems to crystallize coincidently with PP, probably due to its small particle size. The crystallization of PP takes place at temperatures above the bulk value at all compositions in blends compatibilized with PPgMAH and blends without the compatibilizer. By contrast, in blends compatibilized with EBAgFA, SEBSgMAH, and E‐EA‐GMA, the crystallization takes place either at PP bulk temperature or over the temperature range of 76–87°C at the cooling rate of 10°C/min. The amount of the shift cannot be explained solely by the size of the PP dispersion. © 1993 John Wiley & Sons, Inc.
Surface modification of poly(ethylene) in an rf downstream remote plasma reactor
Authors: Holländer A. , Behnisch J. , Zimmermann H. 
Published: April 2003

AbstractPolyethylene (PE) was treated in a remote downstream reactor with oxygen, nitrogen, hydrogen, and mixed gas plasma. The effects of these treatments were investigated by contact angle goniometry and x‐ray photoelectron spectroscopy (XPS). The oxygen plasma treatment allowed a rapid and efficient hydrophilation of the PE, although the samples were placed far outside the main discharge region. In hydrogen plasma treatment, only a small amount of polar functional groups are formed, while the nitrogen plasma results in a surface similar to that in an oxygen plasma treatment. Thirteen percent of oxygen was found by XPS in these samples, while only 3% of nitrogen was present. The mixed oxygen/hydrogen plasma treatment revealed that 0.1% oxygen in the process gas produced a detectable degree of oxidation. By experiments with quenched atomic oxygen, the singlet molecular oxygen (O½Δ) was found to be the major reactive species in the surface reaction in our system. The role and the source of radiation in this reaction is discussed. © 1993 John Wiley & Sons, Inc.
Thermal conductivities of powder‐filled epoxy resins
Authors: Lin F. , Bhatia G. S. , Ford J. D. 
Published: April 2003

AbstractEffective thermal conductivities of powder‐filled epoxy composites were experimentally obtained using a transient method. Fillers used were aluminum and cupric oxide. Comparisons of these data with published correlations indicate that Agari's model can give better fits. Nielsen's model may also give a good prediction of the shape of particles can be determined and values of parameters A and ϕm are available. An alternative method of dealing with parameter C2 in Agari's model is suggested. © 1993 John Wiley & Sons, Inc.
Novolac epoxy resins and positron annihilation
Authors: Suzuki T. , Oki Y. , Numajiri M. , Miura T. , Kondo K. , Shiomi Y. , Ito Y. 
Published: April 2003

AbstractFour kinds of epoxy resins: cresol novolac, tris‐hydroxyphenylmethane, tetramethylbiphenol, and bisphenol A, were cured with phenol novolac epoxy resins. Characteristics of these epoxy compounds were studied by the positron annihilation lifetime (PAL) technique. Glass transition temperatures, thermal expansion coefficients, and volume of intermolecularspace holes among polymer chains were obtained from the lifetime, τ3, of the long‐lived component of ortho‐positronium. It was revealed that, at the glass transition temperature, Tg, the volume of the hole created among polymer chains expanded 1.4 times the volume at room temperature. The smaller flexural modulus of tris‐hydroxyphenylmethane than that of the other samples was explained by the volume of intermolecular‐space holes obtained from τ3. Aging effects were seen in the data of the intensities, I3, of ortho‐positronium, which became smaller after heating the samples above Tg. I3 and τ3 were strongly affected by the density of cross‐linkings, and their chemical structures. The larger the density of cross‐linkings, the smaller I3 and higher Tg were obtained. Epoxy compounds with the higher water‐absorption rates had larger intermolecular‐space holes. © 1993 John Wiley & Sons, Inc.
Thermal properties of 2‐hydroxyethyl methacrylate grafted polypropylene
Authors: Shukla S. R. , Athalye A. R. 
Published: April 2003

Abstract2‐Hydroxyethyl methacrylate (HEMA) was graft‐copolymerized onto polypropylene using ultraviolet radiation in the presence of benzoin ethyl ether as photoinitiator. The parameters of grafting were optimized for getting maximum graft add‐on. The thermal properties of the grafted samples were investigated using differential thermal analysis, thermogravimetric analysis and differential scanning calorimetry. The results have been discussed. © 1993 John Wiley & Sons, Inc.
Porous polyHEMA beads prepared by suspension polymerization in aqueous medium
Authors: Horák Daniel , Lednický František , Řehák Vladimír , Švec František 
Published: April 2003

AbstractA study was made of the effect of the type of low‐molecular‐weight porogen on the properties of polyHEMA beads (sphericity, bead size, porosity, and morphology), prepared by radical suspension copolymerization of 2‐hydroxyethyl methacrylate (HEMA) with ethylene dimethacrylate (EDMA) in aqueous dispersion. The porogen used was cyclohexanol, mixed with various alcohols, hydrocarbons, butyl acetate, or cyclohexanone. Spherical particles, with a size of hundreds of μm and a porosity of up to 68%, can be prepared using a mixture of cyclohexanol and 1‐octanol in a volume ratio of 3:2. The tendency for the particles to agglomerate, observed in the presence of benzyl alcohol, 1‐butanol, or cyclohexanone, can be a consequence of a change in the polymerization mechanism connected with the excessive solubility of these porogens, and thus also the initiator in water. © 1993 John Wiley & Sons, Inc.
A generalized model to predict the viscosity of solutions with suspended particles. III. Effects of particle interaction and particle size distribution
Authors: Sudduth Richard D. 
Published: April 2003

AbstractThe generalized suspension viscosity equation utilized in this study was evaluated with both a packing fraction, φn, and a particle interaction coefficient, σ, as a function of suspension blend composition, f2T. The estimation of the packing fraction, φn, in turn, required the further elucidation of the D5/D1 ratio of particle diameter averages. Blend constants developed in this study allowed evaluation of both the Dx/Dy ratio of particle diameter averages as well as the number‐average particle diameter, D1, as a function of the fraction of one suspension in a blend, f2T. These blend constants were shown to be easily evaluated from each individual suspension prior to blending. The viscosity data of Johnson and Kelsey were shown to be generally predicted as a function of the volume composition when a constant particle interaction coefficient, σ, was assumed. However, a better prediction of the results of Johnson and Kelsey was obtained by assuming that the particle interaction coefficient, σ, was a function of the number‐average particle diameter, D1, of the suspension mixture composition. Consequently, a new approach was identified to evaluate the simultaneous effects of small particles to both increase viscosity as a result of increasing particle interaction as well as to decrease viscosity as a result of improving the particle‐size distribution. © 1993 John Wiley & Sons, Inc.
Bulk and suspension polymerization of styrene in the presence of n‐pentane. An evaluation of monofunctional and bifunctional initiation
Authors: Villalobos Marco A. , Hamielec Archie E. , Wood Philip E. 
Published: April 2003

AbstractThe plasticizing effect of n‐pentane on the rate of bulk free radical polymerization of styrene and molecular weight distribution development has been modeled on the basis of the free volume theory for both monofunctional and bifunctional initiation. A strong decrease in the reaction rate in the late stages of the polymerization, due to the displacement of the onset of the gel effect, has been observed for both types of initiation. This decrease in the polymerization rate limited the terminal conversion to values well below 100% for mono‐functional initiation. However, in bifunctionally initiated polymerization, terminal conversions close to 100% were obtained in spite of the decrease in reaction rate. Contrary to what was expected, the molecular weight distribution obtained at terminal conversion was almost completely insensitive to these changes in polymerization rate. This phenomenon is explained in terms of limited transfer to monomer reactions when n‐pentane is present in the system. In suspension polymerization, the limiting conversion and plasticizing effects of n‐pentane in monofunctionally initiated systems, caused enhanced coalescence leading to suspension set‐up. In bifunctionally initiated systems this enhanced coalescence was completely overcome by the short duration of the particle growth stage, owing to high polymerization rates, and stable suspensions were achieved. For these systems the particle size distributions obtained were similar to that of suspension polystyrene without n‐pentane. © 1993 John Wiley & Sons, Inc.
Polyethylene fibers‐polyethylene matrix composites: Preparation and physical properties
Authors: Teishev Albert , Incardona Silvia , Migliaresi Claudio , Marom Gad 
Published: April 2003

AbstractDrawing on the difference in melting points of UHMPE fiber (150°C) and HDPE matrix (130°C), single‐polymer composites were fabricated under various processing conditions. Because of the chemical similarity of the composite components, good bonding at the fiber‐matrix interface could be expected. The matrix, the fiber, and unidirectional composite laminae were studied using TMA and DSC analyses, a hot‐stage crystallization unit attached to a polarizing microscope, and an universal tensile testing machine. The TMA showed negative thermal expansion of the fiber over the complete temperature range of the experiment. Three regimes of contraction according to the values of the thermal expansion coefficient were detected. DSC analyses of either the fiber or the composite specimens did not show any appreciable changes after various thermal treatments. They also showed no evidence of fiber relaxation during manufacture, probably because of the pressure‐related transverse constraint. The tensile strength and modulus values of the composite appeared to be fairly high and close to those reported for other composites reinforced with polyethylene (PE) fibers. An apparent maximum on the temperature dependencies of tensile properties was observed. A study of the matrix microstructure did not give any proof of transcrystalline growth at the fiber‐matrix interface even for chemical or plasma surface‐treated fibers. © 1993 John Wiley & Sons, Inc.
Three‐dimensional solubility parameters and chemical protective clothing permeation. I. Modeling the solubility of organic solvents in Viton® golves
Authors: Zellers Edward T. 
Published: April 2003

AbstractA model based on the polymer solution theory of Flory and Rehner is presented for estimating the solubility of organic solvents in chemical protective clothing (CPC) polymers using three‐dimensional (3‐D) solubility parameters. Immersion test solubility values of 40 organic solvents in commercial Viton® glove samples are used to develop and assess the performance of the model. It is found that the solvent‐polymer 3‐D solubility parameter differences must be weighted to obtain accurate solubility estimates. However, in most cases, a single weighting factor is sufficient to bring estimated values within a factor of two of experimental values for the members of a given chemical class. The effect of temperature on solubility from 25 to 37°C is predicated within 6%, on average, for the subset of 17 solvents examined. In the companion article that follows, solubility values estimated with this approach are combined with diffusion coefficients, also estimated using 3‐D solubility parameters, to determine solvent‐Viton breakthrough times and steady‐state permeation rates. © 1993 John Wiley & Sons, Inc.
An XPS investigation of polymer surface dynamics. I. A study of surface modified by CF4 and CF4/CH4 plasmas
Authors: Wang Jianqi , Feng Daming , Wang Huanzhong , Rembold Manfred , Thommen Fritz 
Published: April 2003

AbstractFor making the surface hydrophobic, poly(ethylene terephthalate) (PET) films were subjected to treatment by CF4 and CF4/CH4 plasmas, and the PET fabrics, to impregnation (padding) with Oleophobol S for comparison. The electronic structure of the modified surface was differenentiated by XPS (ESCA). The surface dynamics upon heating and dipping into water was investigated by the angle‐dependent XPS technique. Application of the XPS technique to these topics gave a wealth of information. © 1993 John Wiley & Sons, Inc.
Poly(vinyl alcohol) gel sublayers for reverse osmosis membranes. I. Insolubilization by acid‐catalyzed dehydration
Authors: Immelman E. , Sanderson R. D. , Jacobs E. P. , Van Reenen A. J. 
Published: April 2003

AbstractBoth flat‐sheet and tubular composite reverse osmosis (RO) membranes were prepared by depositing aqueous solutions of poly(vinyl alcohol) (PVA) and a dehydration catalyst on asymmetric poly(arylether sulfone) (PES) substrate membranes. The PVA coatings were insolubilized by heat treatment to create stable hydrophilic gel‐layer membranes. The influence of variables such as PVA concentration, catalyst concentration, curing time, and curing temperature was investigated. It was shown that a simple manipulation of one or two variables could lead to membranes with widely differing salt retention and water permeability characteristics. The insolubilized PVA coatings were intended to serve as hydrophilic gel sublayers on which ultrathin salt‐retention barriers could ultimately be formed by interfacial polycondensation. For this purpose, high‐flux gel layers were required, whereas salt‐retention capabilities were not regarded as important. However, the promising salt retentions obtained at 2 MPa (up to 85% NaCl retention and 92% MgSO4 retention) showed that some of these PES–PVA composite membranes could function as mediumretention, medium‐flux RO membranes, even in the absence of an interfacially formed salt‐retention barrier. © 1993 John Wiley & Sons, Inc.