bluuebunny/crossref_metadata_2025 huggingface dataset:
Novolac epoxy resins and positron annihilation
Authors: Suzuki T. , Oki Y. , Numajiri M. , Miura T. , Kondo K. , Shiomi Y. , Ito Y.
Published: April 2003

Four 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

2‐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

A 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

The 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

The 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

Drawing 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

A 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

For 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

Both 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.
Kinetics of curing reaction of epoxide catalyzed by tertiary amine
Authors: Han J. L. , Hsieh K. H. , Chiu W. Y.
Published: April 2003

The kinetic study of the curing reaction of epoxide catalyzed by tertiary amine was carried out through thermal analysis of the reaction by differential scanning calorimetry (DSC). Using infrared spectroscopy (IR) and neutron magnetic reasonance (NMR) analysis, a reaction mechanism for this reaction was proposed. The reaction proceeded to anionic polymerization. An autocatalytic reaction was induced at high concentration of the tertiary amine catalyst. © 1993 John Wiley & Sons, Inc.
Structure and thermal properties of polyether polyurethaneurea elastomers
Authors: Lee Ho Kyung , Ko Sohk Won
Published: April 2003

Three series of polyether polyurethaneurea (PEUU) elastomers based on poly(tetramethylene glycol) (PTMG, MW = 1000 or 2000), 4,4′‐diphenylmethane diisocyanate (MDI), and three kinds of diamine chain extenders, i.e., 4,4′‐diaminodiphenylmethane (DAM), m‐phenylenediamine (MPD), and p‐phenylenediamine (PPD) were synthesized in dimethylformamide or DMF–LiCl solvent by the prepolymer method. The degree of phase separation was higher in the samples with PTMG‐2000 than in those with PTMG‐1000. Three‐dimensional hydrogen bonding between hard segments led to strong hard‐domain cohesion, but solubilized soft segment and the remaining LiCl within hard domains interfered with microstructural ordering of hard segments. According to the TG/DTA analyses, as‐cast PEUU elastomers showed two‐stage degradation behavior at a heating rate of 20°C/min in a nitrogen atmosphere. Initial degradation temperature was closely related with both hard‐segment content and microstructural ordering, i.e., most of the hard segments were degraded in the first stage and samples with less ordered hard segments degraded at a lower temperatures. © 1993 John Wiley & Sons, Inc.
Carboxylated nitrile rubber as a reactive compatibilizer for immiscible blends of poly(vinyl chloride) and epoxidized natural rubber
Authors: Ramesh P. , De S. K.
Published: April 2003

Blends of poly(vinyl chloride) (PVC) and epoxidized natural rubber (ENR) were prepared by melt‐blending and studied using a Monsanto rheometer, infrared spectrophotometer, and dynamic mechanical analyzer. The PVC/ENR blends were found to be self‐crosslinkable, but immiscible at 25/75, 50/50, and 75/25 blend ratios. However, addition of a third reactive polymer, such as carboxylated nitrile rubber (XNBR), can make the ternary blend miscible. The quantity of XNBR required to make the binary blend miscible depends on the blend ratio of the binary PVC/ENR blend and increases as the binary blend ratio changes through 25:75 to 50:50 to 75:25. © 1993 John Wiley & Sons, Inc.
Curing of epoxy resins with dicyandiamide and urones
Authors: Güthner Thomas , Hammer Benedikt
Published: April 2003

The curing of epoxy resins using dicyandiamide (DICY) and combinations of DICY with several uron accelerators as curing agents is investigated. DSC, FTIR, mechanical, and sorption measurements indicate complex multistage curing processes. There is no evidence that the curing reaction is catalyzed by DICY. The optimum stoichiometry is determined as 7 epoxy units per 1 molecule DICY. Contour plots for curing reactions with DICY in presence of Fenuron 3c or TDI‐uron 3d give some information for optimizing technical formulations. © 1993 John Wiley & Sons, Inc.
Structural analysis of methacrylamide‐grafted silk fibers
Authors: Tsukada Masuhiro , Freddi Giuliano , Ishiguro Yosio , Shiozaki Hideki
Published: April 2003

The structural changes and the thermal behavior of silk fibers grafted with methacrylamide (MAA) were investigated as a function of the weight gain. The refractive index parallel to the fiber axis decreased with increasing weight gain, whereas that perpendicular remained almost unchanged. Accordingly, birefringence decreased with a steeper slope in the weight gain range 0–80%, suggesting a lower degree of average molecular orientation. Only small changes in the isotropic refractive index were detected, suggesting that the crystallinity of the fibers remained essentially unaffected by MAA grafting, as confirmed by the X‐ray diffraction data. The molecular orientation in the crystalline regions remained unchanged in the weight gain range 0–60%, then sharply decreased. The strength and the initial tensile resistance of grafted silk fibers decreased both in the dry and wet states, while elongation at break increased in the dry state and remained almost constant in the wet state. The results of the thermal behavior, investigated by differential scanning calorimetry, thermomechanical and thermogravimetric analysis, and dynamic mechanical measurements, were consistent with an increased thermal stability conferred on silk fibers by MAA grafting. The cross‐sectional area of MAA‐grafted silk fibers increased. Moreover, ion‐etched cross sections of the grafted silk fiber showed the presence of fibrils with a diameter larger than that of the untreated control. © 1993 John Wiley & Sons, Inc.
A simple method for determining water‐induced gelling times of isocyanate prepolymers
Authors: Braatz James A.
Published: April 2003

A spectral assay has been developed that permits reliable determination of polymer gelling times. Water‐soluble, isocyanate‐containing polyether prepolymers initiate chain extension on contact with water and after some period of time form a semisolid hydrogel matrix. Techniques based on visual observations used to determine the end point for this process generally produce erratic results. By following scattered transmittance of visible light by an aqueous solution of prepolymer during the gelation process, it is possible to obtain a more objective determination of the gelation time. It was empirically demonstrated that the minimum of the first derivative of the scattered transmittance versus time spectrum correlated with the observed gel time over a wide time scale. © 1993 John Wiley & Sons, Inc.
Application of the kinetic composite methodology to autocatalytic‐type thermoset prepreg cures
Authors: Nam Jae‐Do , Seferis James C.
Published: April 2003

Using a commercial epoxy/carbon fiber prepreg as a model system, cure kinetics of an autocatalytic‐type reaction were analyzed by a general form of conversion‐dependent function first proposed for degradation kinetics of polymers and composites. The characteristic feature of conversion‐dependent function was determined using a reduced‐plot method where the temperature‐dependent reaction rate constant was analytically separated from the isothermal data. Assuming two elementary reaction mechanisms that were expressed by the nth order and autocatalytic kinetic models, they were combined with a composite methodology capable of predicting overall kinetic behavior. The activation energies were determined and favorably compared for both isothermal and dynamic‐heating differential scanning calorimetry experiments in the temperature region for standard epoxy cures at 177°C (350°F). Finally, the proposed model equation demonstrated excellent predictive capability and broad applicability in describing various types of thermoset polymer cure for both isothermal and dynamic heating conditions. © 1993 John Wiley & Sons, Inc.
Thermal degradation study of poly(vinyl chloride): Kinetic analysis of thermogravimetric data
Authors: Jiménez A. , Berenguer V. , López J. , Sánchez A.
Published: April 2003

The thermal degradation of a poly(vinyl chloride) (PVC) resin was studied using a non‐isothermal thermogravimetric technique. Kinetic parameters such as activation energies, reaction orders, and preexponential factors are calculated using integral and differential methods reported in the literature. Advantages and disadvantages of these methods are discussed in order to characterize PVC. © 1993 John Wiley & Sons, Inc.
The kinetics of the polymerization reaction of toluene diisocyanate with HTPB prepolymer
Authors: Kothandaraman H. , Nasar A. Sultan
Published: April 2003

The uncatalysed and catalysed polymerization of a hydroxyl‐terminated polybutadiene with toluene diisocyanate has been studied in toluene solution at four different temperatures. The rate constants (k1, k2) and the activation parameters (Ea1, Ea2, ΔS1‡, ΔS2‡) for the isocyanate groups in the 4 and 2 positions were calculated. It was found that the catalysts enhance the reactivity of the 2 position isocyanate group rather than the 4 position isocyanate group. It was also found that diethylcyclohexylamine has higher selectivity than dibutyltin dilaurate to enhance the reactivity of the isocyanate group in the 2 position. The effect of solvent has also been studied. The reactivity decreased in the following order; benzene = toluene > chlorobenzene > dioxane > nitrobenzene. © 1993 John Wiley & Sons, Inc.
Biodegradation of radiolabeled cellulose acetate and cellulose propionate
Authors: Komarek Ronald J. , Gardner Robert M. , Buchanan Charles M. , Gedon Steven
Published: April 2003

Biodegradation of cellulose acetate and cellulose propionate was conclusively established with a naturally derived mixed microbial culture derived from activated sludge and 14C labeled cellulose esters. Radiolabeled cellulose esters were synthesized with either [1‐14C]‐acetate or [1‐14C]‐propionate and back hydrolyzed to the desired degree of substitution (DS) ranging from 1.77 to 2.64. Biodegradation was measured in an in vitro aerobic culture system that was designed to capture 14CO2 produced by the aerobic microbial metabolism of the cellulose esters. Microorganisms were able to extensively degrade cellulose [1‐14C]‐acetate (CA) with DS ranging from 1.85 to 2.57 over periods of 14–31 days. More than 80% of the original 14C‐polymeric carbon was biodegraded to 14CO2 for CA substrates with a DS of 1.85. CA polymers with a DS of 2.07 and 2.57 yielded over 60% conversion to 14CO2. The amount of biodegradation that was observed with cellulose [1‐14C]‐propionate with DS of 2.11, 2.44, and 2.64 were lower than the corresponding acetyl ester and ranged from 0.09 to 1.1%. However, cellulose [1‐14C]‐propionate with a DS of 1.77 and 1.84 underwent very rapid degradation in the mixed culture system, with 70 to over 80% conversion of labeled polymeric carbon metabolized to 14CO2 in 29 days. The high level of microbial utilization of carbon from both cellulose esters and its conversion to CO2 confirms the biodegradability of these polymers and the potential they have for total mineralization in natural microbiologically active environments. © 1993 John Wiley & Sons, Inc.
Effects of particle shape and size distributions on the electrical and magnetic properties of nickel/polyethylene composites
Authors: Göktürk Halit S. , Fiske Thomas J. , Kalyon Dilhan M.
Published: April 2003

Electrical and magnetic properties of composite materials prepared by incorporating various nickel‐based fillers of different shapes into polyethylene were investigated. The fillers used were nickel powders, nickel filamentary powders, nickel flakes, and nickel‐coated graphite fibers. The particle‐size distributions of the fillers were determined both before and after the processing of the composite samples. A wide range of filler volume fractions were used. In some cases, the volume fraction approached the maximum packing fraction of the solid phase to significantly exceed the percolation threshold. The composite samples were characterized in terms of their volume resistivity, dielectric constant, and magnetic permeability values. Filler particles of asymmetric shapes were very effective in terms of altering the electrical properties of the composite samples. At the highest loading levels of the nickel fillers, the volume resistivity values of the composites decreased by more than 17 orders of magnitude. At such high filler concentrations, the dielectric constant values of the composite samples increased considerably, to values that were greater than 1000. The permeability values of the samples increased linearly with the volume fraction of the nickel filler and were insensitive to the shape of the fillers. The highest relative permeability value measured was 5.8 for composites with 67% by volume of nickel powder. © 1993 John Wiley & Sons, Inc.
Thermal behavior and morphology of rubber‐modified epoxies
Authors: Kim Woo Nyon , Park Chan Eon , Burns Charles M.
Published: April 2003

Rubber‐modified epoxies of tetraglycidyl‐4,4′‐diaminodiphenyl methane and a carboxylterminated copolymer of butadiene–acrylonitrile (CTBN) have been investigated by differential scanning calorimetry, scanning electron microscopy, and micrograph image analysis. Bisphenol‐A (BPA) was used to produce chain‐extended resins by reaction with the epoxy‐terminated rubber. Diaminodiphenyl sulfone was used as a hardener. Partially cured resins were prepared with different amounts of added CTBN and cured in an oven for different cure times at 448 K. From the measured heat of reaction of the samples, a fast curing reaction was observed when BPA was present in the resin formulation. In the study of the morphology, the average size of the domains was seen to increase with the CTBN content. These CTBN‐rich domains appear to include substantial amounts of epoxy material, as indicated by the measured glass transition temperature of the CTBN‐rich phase. The size of domains was observed to range mostly from 0.1 to 5 μm in diameter and to show a slightly bimodal distribution, with modes around 1 μm and 3–4 μm when 15 and 20 phr CTBN was added. © 1993 John Wiley & Sons, Inc.
New use of size exclusion chromatography in kinetics of mechanical degradation of polymers in solution
Authors: Florea Mircea
Published: April 2003

A new method to investigate the mechanical degradation of polymers in solution is described that uses size exclusion chromatograms of the initial polymer and of the degraded sample. The incipient parts of these chromatograms are analyzed to obtain kinetic data about degradation at the level of infinitesimal fractions. The procedure is based on the fact that mechanical degradation of the polymers is a first‐order reaction and macromolecules are cleaved mostly in their central region. The rate constant and the variation in the rate constant with molecular weight are determined in a single experiment, avoiding additional fractionation steps. Moreover, the slope of the size exclusion chromatographic calibration curve is derived, opening new ways to determine polydispersities or even to make rapid calibration for unknown polymers. To verify the method, the rate constant and the molecular weight dependence of the rate constant were determined for the sonic degradation of polystyrene in toluene. The rate constant is found to vary with the square of the molecular weight, and its value is in good agreement with results reported using much more laborious methods. © 1993 John Wiley & Sons, Inc.
Reactive processing of rubber–plastic blends: Role of chemical compatibilizer
Authors: Bhowmick Anil K. , Chiba Tsuneu , Inoue Takashi
Published: April 2003

The present investigation was aimed at understanding the role of chemical compatibilizers like carboxy‐terminated nitrile rubber, amine‐terminated nitrile rubber, liquid carboxylated nitrile rubber, etc. in the reactive processing of a dynamically vulcanized 50 : 50 nylon/ HNBR blend. The interfacial parameters for a bilayer specimen of nylon and rubber and structure parameters during the processing were determined. The interfacial thickness (λ) increased from 48 to 70–80 nm and the interfacial tension (γ∞) decreased from 0.240 to 0.209–0.198 mN/m, depending on the nature and concentration of the compatibilizer. There was, however, an optimum level of the compatibilizer beyond which the thickness did not change significantly. For the ionomeric compatibilizer, λ decreased after the optimum concentration. The increase in λ is ascribed to the formation of a graft copolymer of nylon and rubber and the compatibilization reactions. Structure parameters were dependent upon the sequence of mixing of the compatibilizer. If the compatibilizer and the cross‐linker were added in the rubber and the mixture was then added to nylon, the mean radius of the dispersed particle was smaller over the range of mixing times. The compatibilizers also reduced the particle size at the early stage of mixing due to reduced interfacial tension. In general, the particle size decreased with mixing time, attained a minimum, and then increased. The volume fraction of the interface was also very large for compatibilized systems. The particles were larger, however, when the compatibilizer was first mixed in nylon. SEM studies indicated that the compatibilizer in the latter case was not acting as a surfactant. © 1993 John Wiley & Sons, Inc.
Electrooptical properties of poly(diisopropyl fumarate‐co‐styrene)/cyanobiphenyl‐type liquid crystal composite films
Authors: Choi C. H. , Kim B. K. , Kikuchi H. , Kajiyama T. , Amaya N. , Murata Y.
Published: April 2003

Composite films composed of poly(diisopropyl fumarate‐co‐styrene) (PFS) and nematictype liquid crystal (E8) (40/60 by weight) were prepared by solvent casting in chloroform at room temperature. Scanning electron microscopy measurement showed that a liquid crystal phase is continuously embedded in a spongy‐like PFS martrix. Optical responses of the composite films under the conditions of an externally imposed ac electric field (60–240 Vp‐p,10–1000 Hz), temperature (290–355 K), and a film thickness (8–16 μm), were determined using an He–Ne laser (wavelength 632.8 nm). The results obtained indicated that, under the conditions imposed, the output can be continuously controlled, and the response time is only of several milliseconds or less. In addition, the response to temperature sweep, heating and cooling, was reversible with only a delay, and it was interpreted in terms of the rigidity and thermal stability of the matrix polymer. © 1993 John Wiley & Sons, Inc.
The characterization of short chain branching in polyethylene using fourier transform infrared spectroscopy
Authors: Blitz Jonathan P. , McFaddin Douglas C.
Published: April 2003

The characterization of short chain branching in polyethylene using transmission FTIR spectroscopy is investigated. Traditional methodologies, using the methyl deformation band for qualitative and quantitative analyses, have recognized shortcomings. The methyl and methylene rocking bands, which are more characteristic of short chain branch type, were found to be more useful. Methyl, ethyl, butyl, isobutyl, and hexyl branches are qualitatively and quantitatively characterized in LLDPE copolymers by FTIR spectroscopy. Methyl branches were characterized by an absorbance at 935 cm−1, ethyl branches at 770 cm−1, butyl branches at 893 cm−1, isobutyl branches at 920 cm−1, and hexyl branches at 888 cm−1. Fourier self‐deconvolution was used to resolve overlapping bands for ethyl, butyl, and isobutyl branches. Using calibrations derived for LLDPE copolymers from 13C NMR data, FTIR spectroscopy was also used to characterize LLDPE terpolymers and LDPE resins. The FTIR and NMR data are in qualitative and quantitative agreement. In some cases correction were made to the FTIR results using data obtained from the methyl deformation band. The FTIR technique is less costly and faster than NMR spectroscopy. © 1994 John Wiley & Sons, Inc.
The properties of polyurethanes with mixed chain extenders and mixed soft segments
Authors: Ahn Tae Oan , Jung Soon‐Uk , Jeong Han Mo , Lee Sang Won
Published: April 2003

Series of polyurethaneurea elastomers were prepared from 4,4′‐diphenylmethane diisocyanate, poly(teuramethylene ether) glycol and poly(hexamethylene carbonate) glycol for mixed soft segments, and 1,4‐butanediol and isophoronediamine for mixed chain extenders. Characteristics of the copolymers related with compositions were examined. FT‐IR spectra showed that most of the urea carbonyl groups associated in hydrogen bonding, while urethane carbonyls only partially did so. Thermal and mechanical properties were investigated through differential scanning calorimetry and tensile testing. These thermal and mechanical properties are discussed from the viewpoint of microphase domain separation of hard and soft segments. © 1994 John Wiley & Sons, Inc.
Plasma modification of cellulose fibers: Effects on some polymer composite properties
Authors: Felix Johan , Gatenholm Paul , Schreiber H. P.
Published: April 2003

Cellulose fibers have been surface‐modified by selected cold, microwave plasma treatments. Inverse gas chromatographic (IGC), XPS, and SEM analyses showed surface treatment to be incomplete, but, nevertheless, effective in controllably altering the acid/base interaction balance of fiber surfaces. Surface‐modified fibers were used in composites with polystyrene (PS), chlorinated polyethylene (CPE), and polypropylene (PP) as, respectively, basic, acidic, and neutral matrices. Favorable acid/base interactions led to enhanced mechanical properties and increased glass transition temperatures of composites. Acid/base interaction appears to be an important, though not the sole consideration, in the design of superior systems using cellulose fibers as reinforcing agents. As expected, in the case of PP composites, acid/base considerations proved to be irrelevant. © 1994 John Wiley & Sons, Inc.
Changes in the fine structure of silk fibroin fibers following gamma irradiation
Authors: Tsukada Masuhiro , Freddi Guiliano , Minoura Norihiko
Published: April 2003

The physicochemical changes of silk fibers irradiated with γ‐rays was studied in relation to the amount of absorbed does in the range 0–21 Mrad. The yellowing index (b/L) suddenly increased at low dose for both raw and degummed silk fibers. An equilibrium value was attained from 10 Mrad upward. The tensile properties were significantly affected by exposure to γ‐rays. Both strength and elongation at break decreased at almost the same rate and extent, attaining a final value that was one‐half of the untreated control. The birefringence and isotropic refractive index of exposed silk fibers decreased, the effect being larger in the low dose range, suggesting a decrease of crystallinity and molecular orientation. X‐ray diffraction curves, however, demonstrated that the crystalline structure remained unchanged even after exposure of the highest γ‐ray dose. The thermal behavior evaluated by DSC and TMA measurements showed that the γ‐irradiation induced a slight decrease of thermal stability in irradiated silk fibers, this effect being detectable only at 21 Mrad of the absorbed dose. The dynamic viscoelastic behavior suggested that the thermal movement of the fibroin molecules in the amorphous and crystalline regions increased with increasing absorbed dose, attributing to the physicochemical modifications induced by the ionizing radiations. © 1994 John Wiley & Sons, Inc.
Preparation of flame‐retardant polyethylene foam of open‐cell type by radiation grafting of vinyl phosphonate oligomer
Authors: Kaji Kanako , Yoshizawa Iwao , Kohara Choji , Komal Kuniaki , Hatada Motoyoshi
Published: April 2003

Flame‐retardant polyethylene foam was successfully obtained by grafting a vinyl phosphonate oligomer onto polyethylene foam of an open‐cell type using a simultaneous radiation grafting technique. The foam was impregnated with the oligomer and irradiated in a nitrogen atmosphere with an electron beam. The grafted foam thus obtained was found to pass the three most severe flammability tests that have to be cleared when the foam is to be used for materials where high flame‐retardant property is required. No hydrogen cyanide was detected in burning exhaust gas of the grafted foam. © 1994 John Wiley & Sons, Inc.
Gas transport in polymer membrane at temperatures above and below glass transition point
Authors: Kumazawa H. , Wang J.‐S. , Naito K. , Messaoudi B. , Sada E.
Published: April 2003

The processes of gas sorption and permeation in a polymer membrane at temperatures above and below the glass‐transition point were examined using poly‐4‐methylpentene‐1 (glass‐transition temperature reported to be 40°C) as a membrane material. The permeabilities to O2 and N2 were independent of applied gas pressure at every temperature; the mean permeability coefficient to CO2 increased with increasing gas pressure. The logarithm of the mean permeability coefficient to CO2 increased linearly with gas pressure due to the plasticization effect induced by sorbed CO2. From the sorption isotherms for CO2 at 20 and 30°C it was judged that the glass transition was brought about by sorbed CO2 at temperatures below the glass‐transition point of the pure polymer. © 1994 John Wiley & Sons, Inc.
A study of reverse osmosis separation and permeation rate for sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide) membranes in different cationic forms
Authors: Chowdhury Geeta , Matsuura T. , Sourirajan S.
Published: April 2003

Thin film composite membranes were prepared by coating a thin layer of sulfonated poly(1,4‐dimethyl‐2,6‐phenylene oxide) polymer on the surface of a polysulfone ultrafiltration membrane. The membrane performance was studied when the sulfonate was either in the hydrogen form or loaded fully with an alkali metal cation. It was found that the permeation rate was greater than the pure water permeation rate, when the sulfonate was in the hydrogen form and the feed solution contained an alkali metal chloride solute. The permeation rate increased with an increase in the ionic radius of the alkali metal cation. With respect to membranes in which the sulfonate was loaded with an alkali metal cation, the pure water permeation rate was found to increase with a decrease in the ionic radius of the alkali metal cation. The permeation rate was the same as the pure water permeation rate when the membranes of the latter form were tested for reverse osmosis of aqueous solutions involving either sodium chloride or an organic solute. © 1994 John Wiley & Sons, Inc.
Ultraviolet radiation‐induced graft copolymerization of 2‐hydroxyethyl methacrylate onto polypropylene
Authors: Shukla S. R. , Athalye A. R.
Published: April 2003

Polypropylene staple fibers were grafted with 2‐hydroxyethyl methacrylate (HEMA) using ultraviolet radiation in the presence of three different photoinitiators, uranyl nitrate (UN), ceric ammonium nitrate (CAN), and benzoin ethyl ether (BEE), separately. The parameters of grafting were optimized for obtaining maximum graft add‐on. BEE appeared to be a better photoinitiator than the other two, giving maximum possible graft add‐on. CAN, as a chemical initiator, did not show significant improvement in grafting. The moisture regain of the grafted polypropylene increased in proportion with the graft add‐on. Dyeing with reactive dye could give only light color to the grafted fiber. Possible explanations have been given. © 1994 John Wiley & Sons, Inc.
Comparison of hydrodynamic and rheological properties of dilute solutions of a styrene‐hydrogenated butadiene copolymer in aliphatic solvents by light scattering and viscometric techniques
Authors: Bezot P. , Hesse–Bezot C. , Elmakoudi B. , Constants B. , Faure D. , Hoornaert P.
Published: April 2003

Dilute solution of a styrene‐hydrogenated butadiene copolymer, a viscosity index improver, were studied by static and dynamic light‐scattering techniques. In n‐hexane (a model solvent for paraffinic oils) and a mineral base oil, aggregation is observed below 30°C. In cyclohexane (a model solvent for napthenic oils) only isolated polymers are present in the whole temperature range.

Kinematic viscometric measurements from 20 to 60°C in the mineral oil show a continuous increase of the intrinsic viscosity together with a decrease of kH, the Huggins coefficient, from 2.5 to 0.5. At shear rates between 5000 and 40000s−1, a large shear thinning is observed at room temperature for the polymer in the mineral base oil. This effect progressively disappears as the temperature increases and the suspension becomes Newtonian near 100°C. All results can be interpreted in terms of micelle formation. © 1994 John Wiley & Sons, Inc.
Calcium alginate gel fibers: Influence of alginate source and gel structure on fiber strength
Authors: Moe Størker , Skjåk‐Bræk Gudmund , Smidsrød Olav , Ichijo Hisao
Published: April 2003

The low‐deformation extension modulus was measured for Ca–alginate gel fibers prepared from alginates of different compositions and molecular weights. The modulus showed an increase with increasing molecular weight for alginates of the same composition and sequence parameters. Fibers prepared with an inhomogeneous polymer concentration profile showed higher moduli than did fibers with a homogeneous polymer concentration profile. The higher modulus observed for fiber prepared from an alginate with low Ca2+ affinity is tentatively explained as resulting from a higher degree of polymer chain alignment. © 1994 John Wiley & Sons, Inc.
Composites of anionic (co)polyamides (nylon 6/nylon 12) with short glass E‐fibers. Preparation and properties
Authors: Arvanitoyannis I. , Psomiadou E.
Published: April 2003

The recent high demand of thermoplastic composites has induced an extensive experimentation and utilization of polyamides as thermoplastic sheet composites. The hand layup technique was used for the preparation of the glass fiber polyamide composites studied here. The percentage crystallinity of the composites was determined with a variety of techniques such as differential thermal analysis (DTA), wide‐angle X‐ray diffraction (WAXD) patterns, and density measurements. Glass transitions (Tg) and melting temperatures (Tm) were determined with DTA and dynamic mechanical thermal analyzer (DMTA) measurements. Finally, the mechanical properties (stress–strain curves and compression tests) were investigated and the results were correlated to the glass fiber content, and the percentage of the comonomer unit (caprolactam and laurolactam) in the polyamide composite. © 1994 John Wiley & Sons, Inc.
Characteristics of permeation and separation for propanol isomers through poly(vinyl alcohol) membranes containing cyclodextrin
Authors: Miyata Takashi , Iwamoto Tooru , Uragami Tadashi
Published: April 2003

Poly(vinyl alcohol) membranes containing cyclodextrin (CD–PVA membrane) were prepared and characteristics of permeation and separation for propanol (PrOH) isomers through the CD–PVA membranes were investigated by pervaporation and evapomeation. Evapomeation was more effective for the separation of PrOH isomers through the CD–PVA membrane than was pervaporation. The CD–PVA membrane more preferentially permeated n‐PrOH than i‐PrOH from their mixtures. In particular, the mixture of 10 wt % n‐PrOH concentration was concentrated to about 45 wt % through the CD–PVA membrane. Both permeability and selectivity for n‐PrOH were improved with an increase of CD content in the membrane. The results were supported by the fact that the affinity of CD for n‐PrOH was stronger than that for i‐PrOH. The permeation mechanism of PrOH isomers through the CD–PVA membrane is discussed based on the solution–diffusion theory. © 1994 John Wiley & Sons, Inc.
The influence of processing terms of chitosan membranes made of differently deacetylated chitin on the crystalline structure of membranes
Authors: Urbanczyk G. W. , Lipp‐Symonowicz B.
Published: April 2003

The crystalline structure of chitosan membranes made of a high degree of (90%) and low degree of (60%) deacetylated chitin by various regeneration processes was studied. The results of X‐ray and IR spectroscopy investigations testify that the type of crystalline structre, the degree of crystallinity, and the average lateral crystallite size depend basically on the deacetylation degree of the chitin utilized in preparing the membranes. © 1994 John Wiley & Sons, Inc.
The ductile‐to‐quasi‐brittle transition of particulate‐filled thermoplastic polyester
Authors: Li J. X. , Silverstein M. , Hiltner A. , Baer E.
Published: April 2003

The effects of various filler characteristics on the ductility of filled amorphous copolyester, Kodar 6763, have been examined. The five fillers in the study included two calcium terephthalates with different particle‐size distributions and three calcium carbonates, also with different particle‐size distributions. One of the calcium carbonate fillers had received a surface treatment. The increase in Young's modulus with increasing filler content was the same for all fillers and was satisfactorily described by Kerner's equation. The only filler to affect the yield stress was the surface‐treated calcium carbonate; in this case, the decrease in yield stress was attributed to cracking and splitting of aggregated particles. A sharp drop in fracture strain was observed with increasing filler content. This ductile‐to‐quasi‐brittle transition occurred when the fracture mode changed from fracture during strain‐hardening of neck propagation to fracture during neck formation. The critical filler content of the ductile‐to‐quasi‐brittle transition varied from one filler to another. A simple model qualitatively described the decrease in critical filler content with increasing breadth of the particlesize distribution and, in particular, with increasing volume percent of large particle in the distribution. © 1994 John Wiley & Sons, Inc.
A simple dilatometer for thermoset cure shrinkage and thermal expansion measurements
Authors: Snow Arthur W. , Armistead J. Paul
Published: April 2003

A simple capillary and bulb mercury dilatometer designed for specific volume measurements on thermoset resin systems during the curing reaction and as a function of temperature is described. The design, calibration, operation, data treatment, and error analysis are presented in detail, with data on the bisphenol A dicyanate resin system used as an example. Particular attention is directed at experimental difficulties such as monomer/prepolymer degassing, filling the dilatometer under vacuum, adhesive distortion of the curing resin on the dilatometer bulb, and the dilatometer bulb to capillary connection problem. © 1994 John Wiley & Sons, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Interfacial synthesis and characterization of random and segmented block bisphenol A–tetrabromobisphenol A copolycarbonates
Authors: Marks M. J.
Published: April 2003

The chain sequence architecture of bisphenol A–tetrabromobisphenol A copolycarbonates depends on the process employed to prepare them. An interfacial process involving a single‐step phosgenation produces a segmented block copolymer, contrary to previous assumptions. An interfacial two‐step phosgenation process allows the preparation of random copolycarbonates. In each process the control of the pH of the acqueous phase of the two phase reaction mixture is required to achieve complete comonomer conversion to copolymer and to obtain the desired sequence architecture. The chain sequence architecture of these copolycarbonates can be estimated by examination of their Fourier transform infrared spectra. The relative bandwidth of the carbonate stretching band is roughly proportional to the copolycarbonate number average sequence length, allowing the facile distinction between block and random copolymers. The number average sequence lengths of these copolycarbonates were quantified by carbon‐13 NMR spectroscopy. These analyses showed that the one‐step phosgenation process yields segmented block copolycarbonates having number average sequence lengths from about 4 to 9, and the two‐step phosgenation process produces random copolycarbonates having sequence lengths from 1.6 to 2. The distribution of the aromatic carbon triads of these random copolymers shows them to have an alternate‐segmented block architecture, which is consistent with the synthesis conditions, rather than a statistically random distribution of comonomer segments. Dynamic mechanical analysis of two of these copolycarbonates shows a dependence of their low temperature secondary transitions on the copolymer sequence structure. A segmented block copolycarbonate, having a number average sequence length of about 4, displays two distinct peaks in its tan δ curve at temperatures corresponding to those transitions observed in the respective homopolymers. The tan δ curve of a random copolycarbonate shows a single low temperature secondary transition midway between those of the homopolymer. © 1994 John Wiley & Sons, Inc.
Synthesis, characterization, and coating applications of chlorinated hydroxyrubber
Authors: Thames Shelby F. , He Z. Alex
Published: April 2003

Chlorinated hydroxyrubber has been synthesized via the chlorination of hydroxylated liquid natural rubber. The formulation examples and coatings properties of two‐component chlorinated hydroxyrubber polyurethane coatings are described. © 1994 John Wiley & Sons, Inc.