bluuebunny/crossref_metadata_2025 huggingface dataset:
Photopolymerization using sensitizers of binary system of aromatic hydrocarbon and amine
Authors: Kubota Hitoshi , Ogiwara Yoshitaka
Published: April 2003

Photopolymerizations of acrylonitrile and methyl methacrylate, using binary sensitizers of aromatic hydrocarbon and amine, were investigated at 30°C in N,N‐dimethylformamide under the irradiation with a light of λ > 300 nm. Naphthalene, anthracene, and phenanthrene were employed as aromatic hydrocarbons in the experiment. The binary system was effective for the initiation of the monomers. The combinations of naphthalene with tertiary amines, triethylamine and N,N‐dimethylaniline, were remarkably effective among various combinations. The rate of polymerization with naphthalene–triethylamine sensitizer was observed to be proportional to the first, ½, and ½ powers of monomer, naphthalene, and triethylamine concentrations, respectively. The kinetics of the photopolymerization are proposed, and the initiation schemes are discussed, comparing them with those in the system sensitized by aromatic ketone–amine reported previously.
Photooxidation of amine crosslinked epoxies I. The DGEBA–DDM system
Authors: Bellenger V. , Verdu J.
Published: April 2003

The photooxidation in the solar UV range of tridimensional networks based on the diglycidyl ether of bisphenol A (DGEBA) and diaminodiphenyl methane (DDM) is characterized by the formation of carbonyl, amide, and hydroperoxide groups and by at least two types of chromophores. One absorbs strongly in the near UV, violet, and blue regions, and is responsible for the development of an internal screening effect leading to a decrease of photooxidation rate during exposure. The other, which absorbs in the red region (γmax = 615 nm), is responsible for the green color of oxidized smaples and is derived from the oxidation of the diamine bridge. The influences of hardener concentration and thermal treatments are explained in terms of a stabilizing effect of unreacted DDM molecules and a photoinitiating effect of some thermal‐oxidation products, presumably hydroperoxides.
Chemorheology of thermosetting resins. I. The chemorheology and curing kinetics of unsaturated polyester resin
Authors: Han Chang Dae , Lem Kwok‐Wai
Published: April 2003

The rheological properties and curing kinetics of a general‐purpose polyester resin have been determined during isothermal cure. Both steady and oscillatory shearing flow properties were determined using a cone‐and‐plate rheometer, and the curing kinetics were determined using a differential scanning calorimeter (DSC). It was found that, as cure progresses, the steady shear viscosity increases very rapidly with cure time at all shear rates investigated, and normal forces show negative values at low shear rates and positive values at high shear rates. The observed negative normal forces are believed to result from material shrinkage during cure, and positive normal forces from the deformation of large molecules, formed by crosslinking reactions during cure. Note that, in a cone‐and‐plate rheometer, the shrinkage force acts in the direction opposite to that of normal forces. It is, therefore, concluded that extreme caution is needed in the interpretation of normal force measurements with thermosetting resins, subjected to steady shearing flow. Dynamic measurements seem to offer some insight on the onset of gel formation. More specifically, we have found that, when the unsaturated polyester resin was cured at a fast rate, the time at which a maximum in the loss modulus G” occurs coincides reasonably well with the time tη∞ at which the steady shear viscosity η approaches infinity. However, at a slow rate of cure, the time at which tan δ equals unity agrees fairly well with tη∞. DSC measurement has permitted us to determine the degree of cure as a function of cure time and the kinetic parameters in an empirical expression for the curing kinetics advanced by Kamal and co‐workers. By combining the rheological and DSC measurements, we have constructed plots describing how the viscosity increases with the degree of cure, at various values of isothermal curing temperature.
Compatibility of nylon 6 and PMMA–oligoamide graft copolymer
Authors: Seo Seung Won , Jo Won Ho , Ha Wan Shik
Published: April 2003

PMMA–oligoamide graft copolymers, which were prepared by reacting poly(methyl methacrylate‐co‐methacryloyl chloride) with oligoamide, were blended with nylon 6. The compatibility was examined by measuring thermal properties such as melting point and crystallization temperature. It was observed that the melting point was significantly depressed as the grafted PMMA was added to nylon 6, suggesting that the blend is a miscible system. It was concluded that hydrogen bonding between amide groups of the two polymers enhanced the miscibility.
Electrical and photovoltaic properties of Pb/trans‐ (CH)x and Pb/[CH(AsF5)y]x schottky barriers
Authors: Donckt E. Vander , Kanicki J. , Fedorko P.
Published: April 2003

The rectifying and photovoltaic properties of Pb/trans‐polyacetylene/graphite sandwich cells have been examined. The dependence of the short‐circuit current density (Jsc) and open‐circuit voltage (Voc) on light intensity have been determined. Some data on a Pb/AsF5 lightly doped polyacetylene graphite cell are also reported.
Semi‐ and fully interpentrating polymer networks based on polyurethane–polyacrylate systems. IV. Grafted semi‐1‐interpenetrating polymer networks
Authors: Hourston D. J. , Zia Y.
Published: April 2003

A series of semi‐1‐IPNs containing 40% polyurethane and 60% polymethyl acrylate was synthesized using Adiprene L‐100, trimethylol propane, and polybutadiene diol. This diol was chosen to yield polyurethanes with a large number of potential graft sites for the methyl acrylate which was polymerized after the polyurethane network had been formed. A series of linear polyurethane–polymethyl acrylate blends, covering a range of compositions, was also prepared. The polyurethane for these polyblends was synthesized from Adiprene L‐100 and butane‐1,4‐diol. Both sets of materials were investigated by dynamic mechanical analysis. On the basis of a comparison of solubility parameters, the polyurethanes and polymethyl acrylate would be expected to be incompatible. In the dynamic loss modulus‐temperature plots of the polyblends there was a significant shift of the polyurethane Tg to higher temperature, but the polymethyl acrylate transition did not shift. The polyurethane transitions of the semi‐1‐IPNs were also shifted, but considerably more than in the case of the polyblends. For both systems, it was postulated that grafting had occured to a significant extent. With the semi‐1‐IPNs, it was found that as M̄c decreased the extent of grafting apparently increased. This was rationalized on the grounds that as the network chain lengths decrease, a higher proportion of the methyl acrylate monomer, prior to polymerization, was close to polyurethane segments and that this is a situation likely to lead to more grafting.
Dynamic moduli for short fiber‐CR composites
Authors: Ashida Michio , Noguchi Toru , Mashimo Satoshi
Published: April 2003

The dynamic moduli, E′ and E″, and tan δ for nylon–CR and PET–CR composites with unidirectional short fibers were studied as a function of temperature by using a Rheovibron. The temperature dependence of tan δ showed two dispersion peaks for nylon–CR composite. The peak at −28°C corresponded to the main dispersion of CR and the peak at 100°C to the α‐dispersion of nylon 6. For a PET‐CR composite, in addition to the individual dispersion of CR and PET, a small and broad peak was observed at about 90°C. The angular dependence of E′ indicated that the short fibers assumed good orientation. The storage modulus for the composites was given by the parallel model as E′ = Vf′Ef + VmE′m., where E′c, E′f and E′m were the storage modulus for the composite, fiber, and matrix and Vf and Vm were the volume fraction of fiber and matrix, respectively. In the transverse direction of fiber, the peak values of tan δ at −28°C were given by the following equation; tan δc = tan δm − δVf, where tan δc and tan δm are the loss tangent for the composite and matrix, respectively, and α is coefficient depending on fiber type. The results indicated that a region with strong interaction was formed between fibers and CR matrix.
A stochastic model for predicting the service life of photolytically degraded poly(methyl methacrylate) films
Authors: Martin Jonathan W.
Published: April 2003

A stochastic model has been proposed and partially validated for predicting the service life of a nominal population of polymethyl methacrylate films subjected to photolytic degradation. Here, service life is defined as the time after which an unacceptable portion of a nominal population of PMMA films subjected to photodegradation have failed; failure occurs when a performance property of the film falls below a predesignated minimum value. The stochastic model has two parts. The first part uses a Poisson distribution in computing the probability that exactly K photon related chain scissions will occur in the film in the interval [0, t). The parameter of the Poisson distribution is made functionally dependent on temperature and the intensity of radiation absorbed. The second part determines the probability that a performance property will be greater than a minimum value after K chain scissions. This part is called the damage process. Together, the two parts of the model form a compound Poisson process. The main points of the models are validated against 25 published data sets. The plausibility of the Poisson process was substantiated for modeling the number of chain scissions occurring in the interval [0, t). Also, it was demonstrated that the expected change in two performance properties of the films was functionally related to the expected number of chain scissions.
Dynamic mechanical properties of partially oriented polyester (POY) and draw‐textured polyester (PTY) yarns
Authors: Miller R. W. , Murayama T.
Published: April 2003

Spinning speed is one of the most important process parameters for change in properties of yarn and efficiency of polyester production. In this paper the effect of spinning speed (3000–6200 ypm) on dynamic mechanical properties is presented, and shows a good qualitative picture on the influence of structure change on the dynamic modulus and the height and position of glass transition peak on POY (partially oriented polyester) and PTY (draw‐textured polyester) yarns. The dynamic moduli of POY yarns in a temperature range of 25–160°C are increased with increasing spinning speed. Large glass transition peaks (α peak) are observed for POY yarn spun at 3000 and 2800 ypm at about 98°C. This indicates that the yarns are low oriented with low crystallinity (5–6%). But the Tg of POY spun at 5600 or 6200 ypm is about 125°C and shows about 35% crystallinity with high amorphous orientation. An approximately linear relation was found between the height of the loss peak (tan δ) and the degree of amorphous orientation (fa) by using these analyses.
Diffusion of dyes in polyester fibers. III. Time delay in establishment of the equilibrium concentration of dye at fiber surface
Authors: Narȩbska Anna , Ostrowska‐Gumkowska Barbara , Krzystek Henryk
Published: April 2003

In the dyeing process of the copolyester fiber Dilana with the disperse dye Synthene Scarlet P3GL, a deviation from the simple model of Fickian sorption occurs. It manifests itself as a time delay in establishment of the equilibrium dye concentration at the fiber surface. As has been stated, the variation of Cs (the surface dye concentration) with time of dyeing fits the equation; Cs = C∞ (1− e−βt). Regarding the relation of Cs to t, the diffusion coefficient of the dye in the studied fiber has been calculated by the theoretical equation reported in Crank's monograph. It has been proved that the experimental data on kinetics of dyeing the fiber Dilana with Synthene Scarlet P3GL fit considerably better the tested equation than the classical Hill's equation.
Chemorheology of thermosetting resins. IV. The chemorheology and curing kinetics of vinyl ester resin
Authors: Han Chang Dae , Lem Kwok‐Wai
Published: April 2003

The rheological properties and curing kinetics of a vinyl ester resin have been determined during isothermal cure. Both steady and oscillatory shearing flow properties were determined using a cone‐and‐plate rheometer, and the curing kinetics were determined using a differential scanning calorimeter (DSC). Also determined were the rheological properties and curing kinetics of the resin when it had been thickened using magnesium oxide (MgO), in the presence of calcium carbonate (CaCO3) as filler and polyvinyl acetate (PVAc) as low‐profile additive. The steady shearing flow behavior observed with the vinyl ester resin was found to be very similar to that observed with a general‐purpose polyester resin, reported in Paper I of this series [C. D. Han and K. W. Lem, J. Appl. Polym. Sci., 28, 3155 (1983)]. However, a significant difference in the oscillatory shearing flow behavior was found between the two resins. We have concluded that dynamic measurement is much more sensitive to variations in resin chemistry than steady shearing flow measurement. DSC measurement has permitted us to determine the degree of cure as a function of cure time. By combining the rheological and DSC measurements, we have constructed plots describing how the viscosity increases with the degree of cure, at various isothermal curing temperatures.
Polymer characteristics and fracture morphology of radiation‐polymerized styrene‐impregnated mortar
Authors: Bhattacharya Vijay K. , Maiti Mrinal M. , Adhikari Basudam , Maiti Sukumar
Published: April 2003

Mechanical and durability properties and the fracture morphology of polystyrene‐impregnated mortar composites prepared by impregnation of styrene and its in situ polymerization by gamma radiation have been studied. Variation of flexural strength of the composites, percent extractable polystyrene, and its molecular weight suggest crosslinking of the impregnated polymer under the influence of prolonged gamma irradiation. Moreover, crosslinking appears to contribute toward the improvement in flexural strength but has little effect on durability properties. SEM micrographs of the composites reveal a very weak cement–polymer interfacial bonding which is believed to be responsible for poor durability properties of the composites.
Effect of crystallinity on mechanical properties of miscible polycarbonate–copolyester blends
Authors: Preston W. E. , Barlow J. W. , Paul D. R.
Published: April 2003

Normally amorphous miscible blends of a copolyester and polycarbonate in the form of injection molded bars and extruded film were thermally annealed above the blend Tg to cause the copolyester component to crystallize, and the resulting mechanical properties were evaluated. The properties were found to depend in a complex way on blend composition, annealing conditions employed, the initial state of molecular orientation, and the process history.
Polyurethane–urea elastomers as working substances in rubber heat engines
Authors: Lyon R. E. , Wang D. X. , Farris R. J. , MacKnight W. J.
Published: April 2003

The possibility of using synthetic elastomers as working substances in a rubber heat engine was investigated at the laboratory and pilot scale. Two polyurethane–urea elastomers were subjected to expermental heat engine cycles at a variety of strains and temperature differences. It was found that optimum power and thermal efficiency were obtained at small strain perturbations where the elastomers were close to mechanical equilibrium. Crystallization of the rubbery phase during large strain perturbations is a nonequilibrium process which should be avoided. Quasi‐ideal rubber behavior is approached in the pilot‐scale heat engine which supports these conclusions.
Size exclusion chromatography of urea formaldehyde resins in dimethylformamide containing lithium chloride
Authors: Ludlam P. R. , King J. G.
Published: April 2003

A rapid, reproducible method for investigating the molecular mas distribution of urea formaldehyde resins by size exclusion chromatography has been developed. By using concentrated lithium chloride solution to prepare the sample, materials of high viscosity and high molecular mass can be easily dissolved. Chromatography in dimethyl formamide containing lithium chloride eliminates hydrogen bonding and ensures that realistic values for molecular mass averages are obtained.
Effect of the thermal histories on case II sorption kinetics: Test of a kinetic theory for swelling
Authors: Sarti G. C. , Apicella A. , De Notaristefani C.
Published: April 2003

Case II sorption kinetics have been analyzed for PS–n‐hexane systems. Samples of polystyrene characterized by several different annealing histories were used. For all thermal histories, the n‐hexane sorption kinetics at several temperatures were measured, as well as some relevant mechanical properties of the glassy matrix, e.g., density and initial stress for crazing. The main influence of the thermal history is to appreciably alter the initial stress for crazing σc, as well as the swelling kinetics. The σc curve vs. annealing time is seen to go through a minimum which is paralleled, at 40°C, by a maximum in the swelling kinetics. The independent mechanical and sorption data obtained were compared with a recently proposed [G. C. Sarti, Polymer, 20, 827 (1979); G. C. Sarti and A. Apicella, Polymer, 21, 1031 (1980)] theory for Case II kinetics, which is shown to be particularly suitable to describe the observed behavior.
Mercerization of cellulose. I. X‐ray diffraction evidence for intermediate structures
Authors: Okano T. , Sarko A.
Published: April 2003

A study of the mercerization of ramie cellulose was begun using x‐ray diffraction, in order to determine the types of alkali–cellulose structures that occur as intermediates during the conversion of cellulose I to cellulose II. A total of five unique alkali–celluloses (Na–celluloses) could be generated reproducibly, depending only on the alkali concentration used. The reproducibility was enhanced by slowing down the mercerization process, by laterally compressing the fibers in capillary tubes. The five structures, named Na–celluloses I, IIA, IIB, III, and IV, were of two types based on their crystallographic fiber repeats. The first type was represented by Na–celluloses I, III, and IV, all exhibiting a ca. 10 Å repeat. The second type was represented by Na–celluloses IIA and IIB, with a ca. 15 Å repeat. The latter structures are possibly based on a threefold helical chain conformation, which has not been seen in crystalline celluloses. All Na–cellulose structures exhibited a reasonable degree of crystallinity and high degree of fibrous orientation. They formed a definite interconversion scheme, marked by crystalline‐to‐crystalline phase transformations.
Kinetics of phthalic anhydride/ethylene carbonate reactions
Authors: Fagerburg D. R.
Published: April 2003

The kinetics of the polymerization of phthalic anhydride with ethylene carbonate to give poly(ethylene phthalate) were studied to elucidate the reaction mechanism. Zero‐order kinetics were observed to varying degrees of reaction depending upon reaction temperature. Although no clear‐cut overall reaction order could be established, previously proposed mechanisms involving decomposition of the carbonate as the first step of the reaction were ruled out. The chain propagation step was on the order of or faster than the initiation step of the reaction. Virtually no ether–glycol species were formed during the polymerization. A new mechanism was proposed for the polymerization.
Study of mechanical properties of urethane‐chlorinated rubber graft copolymer system. I
Authors: Anbazhagan K. , Reddy C. Rami , Joseph K. Thomas
Published: April 2003

The isocyanate‐terminated urethane prepolymer was prepared from toluene diisocyanate and a mixture of castor oil‐polypropylene glycol (PPG) (MW 2000). The chlorinated rubber (CR) graft copolymers (A and B) containing small percentage of hydroxyl groups were mixed with the urethane prepolymer in different proportions (1:1, 2:3, and 1:2), and the films were cast using these systems. Tensile strength and percent elongation were evaluated for A and B series with and without triethanolamine (TEA). Morphological characteristics of the films were also studied by using a scanning electron microscope (SEM). Deviations noticed in tensile strength values at yield as well as at break for A and B series and for the samples cured with additional TEA have been discussed.
Thioether glycidyl resins. V. Products of condensation of 1,4‐, 1,5‐di(mercapto)naphthalene and 4,4'‐di(mercapto)diphenyl with epichlorohydrin
Authors: Charmas Władysław
Published: April 2003

Thioether glycidyl resins produced by condensation of isomeric 1,4‐, 1,5‐di(mercapto)naphthalenes and of 4,4'‐di(mercapto)diphenyl with epichlorohydrin were obtained by heterophase alkaline condensation in water and isopropyl alcohol solution by sodium hydroxide solution. Their structure was determined by elemental analysis and IR and NMR spectra. The physical and chemical properties were determined. Some properties of the resins were determined during thermal and chemical curing with the curatives typical for epoxy resins. The cured compounds were characterized from derivatographic, thermomechanical, and mechanical studies.
Metals as synergistic fire retardants in polyethylene–silicone blends
Authors: Maclaury M. R. , Schroll A. L.
Published: April 2003

The role of lead compounds in blends of polyethylene and silicone has been studied as a flame retardant. It has been established that these compounds work in the solid phase and that a gas‐forming reaction is important to produce a foamed char which retards further combustion.
Surfactant titration technique: An improved approach for determining latex adsorption isotherm endpoints
Authors: Maurice Alvin M.
Published: April 2003

A unique approach has been developed for determining surfactant titration end points via computer analysis utilizing nonlinear regression. This approach fits the data to an equation and then mathematically solves this equation to yield a reproducible endpoint. In this study, this computer program was utilized to interpret titration data for model acrylate, methacrylate, and styrene homopolymer and copolymer systems.
Characterization of Na ion‐sensitive solvent polymeric membranes based on a neutral carrier
Authors: Maruizumi Takuya , Miyagi Hiroyuki , Takata Yoshinori , Kobayashi Teruaki
Published: April 2003

The states in the surface and the bulk phases of Na ion‐sensitive polymeric membranes based on a synthetic carrier were investigated using SEM, IR, 13C‐NMR, and GC. The 13C‐NMR study revealed that conformation change of the carrier took place when the carrier was incorporated into the membrane phase. From SEM, IR, and 13C‐NMR experiments with a deteriorated membrane, the conformation change of the carrier was proposed as one of the deterioration factors other than the decrease in the diffusion coefficient of the carrier in the membrane phase.
Polymerization of p‐cresyl glycidyl ether catalyzed by imidazoles I. The influence of the imidazole concentration, the reaction temperature, and the presence of isopropanol on the polymerization
Authors: Berger Joseph , Lohse Friedrich
Published: April 2003

The polymerization of p‐cresyl glycidyl ether catalyzed by imidazoles has been investigated as a model reaction for the polymerization of technical epoxy resins. The dependence of oligomer yield on time, temperature, and imidazole concentration, the distribution of the polymerization degrees, and the influence of isopropanol have been studied. The reaction rate and the average degree of polymerization are affected by the presence or absence of a secondary nitrogen on the imidazole, i.e., different results are obtained when 2‐ethyl, 4‐methyl imidazole (EMI) or 1‐methyl imidazole (1‐MIA) are used. 1‐MIA seems to be “precursor” of the catalyst rather than a catalyst by itself. The comparisons of CGE polymerizations catalyzed by 1‐MIA in the absence and presence of isopropanol show only quantitative differences: The polymerization in the presence of isopropanol is faster, and the average degree of polymerization is shifted to higher values. The activation energies of CGE polymerizations catalyzed by different imidazoles have been determined.
Forced oscillations in continuous flow stirred tank reactors with nonlinear step growth polymerization
Authors: Gupta Santosh K. , Nath Sunil , Kumar Anil
Published: April 2003

The self‐step growth polymerization of RAf monomers in homogeneous, continuous flow stirred tank reactors (HCSTRs) is simulated under conditions of periodic feed concentration (with frequency ω and amplitude α). By having periodic operation, the polydispersity index of the polymer is found to increase by about 35% over the values at steady state. Periodic operation of HCSTRs is found to lead to gelation only for certain values of the frequency and the dimensionless residence time τ*. Gelling envelopes have been obtained to give conditions under which HCSTRs should be operated. These envelopes can be described in terms of two critical dimensionless residence times, τ and τ such that nongelling operation is always ensured when τ* < τ. For τ* > τ, periodic operation always leads to gelation, and HCSTRs cannot be used. For τ < τ* < τ, the gelling behavior is found to depend on the functionality f, amplitude α, and the dimensionless residence time τ*.
Use of sterically stabilized polymer colloids as electrostatically‐based liquid developers
Authors: Croucher M. D. , Lok K. P. , Wong R. W. , Drappel S. , Duff J. M. , Pundsack A. L. , Hair M. L.
Published: April 2003

Liquid immersion development (LID) of a latent electrostatic image has become established as an important alternative to dry toning during the past decade. In this development method, a charged, colloidally stable colored particle that is dispersed in a dielectric fluid undergoes electrophoresis under the influence of an applied field. These particles then neutralize a latent electrostatic image of opposite polarity, which resides on either a photoreceptor drum or on dielectric paper. This results in a hard copy of the latent image being obtained. In this paper we outline the physicochemical properties that are demanded of a liquid toner and describe an alternative approach to the preparation of a LID materials package. This new approach utilizes a nonaqueous polymer colloid as the vehicle, which when colored and charged, gives a LID toner. The advantage of nonaqueous dispersions is that the steric stabilizer is irreversibly attached to the particle. Since desorption of the stabilizer is not a problem, these materials are colloidally stable for an indefinite period of time. The particles were colored using both dyes and pigments. While neither approach was entirely satisfactory, the feasibility of coloring such particles was demonstrated. A positive charge was imparted to the particles by specific adsorption of the cation of a metal soap at the polymer–fluid interface. It was found that these experimental LID toners were able to develop a latent electrostatic image in a commercially available printer with the image being well fixed to the paper. While this approach has not been optimized, it appears to be an attractive route for preparing novel LID developers.
Properties of UV‐curable polyurethane acrylates: Effect of reactive diluent
Authors: Speckhard T. A. , Hwang K. K. S. , Lin S. B. , Tsay S. Y. , Koshiba M. , Ding Y. S. , Cooper S. L.
Published: April 2003

Several families of UV‐cured polyurethane acrylates were synthesized, and the effects of reactive diluent type and content on their physical properties were investigated. Increasing reactive diluent content promoted the development of a second, high glass transition temperature phase in all the materials, thereby leading to increased strength and modulus. Changes in the extensibility of the samples upon addition of reactive diluent were inversely related to the effect of the diluent on the crosslink density. The effects of using different reactive diluents (di‐, tri‐, and tetraethylene glycol diacrylate and N‐vinyl pyrrolidone) on the physical properties of the samples were attributed to differences in the softening point (Tg) of the homopolymer reactive diluents and the relative compatibility of the reactive diluents with the urethane acrylate segments.
Photopolymer morphology: Phase separation during polymerization
Authors: Maerov S. B.
Published: April 2003

Morphology and phase structure were studied before and after photopolymerization for the binder–monomer system: poly(styrene/sec‐butylmaleate)(50/50)–trimethylolpropane triacrylate (TMPTA)(75/25). Films supported on a suitable substrate were measured by dynamic mechanical analysis and by dielectric relaxation before and during photocrosslinking. Such film support techniques also allow a variety of physical and chemical treatments to be carried out to determine structure changes. Two phases and a secondary transition were identified. The shift in temperature of both Tg's during photopolymerization and concurrent, fracture‐surface electron photomicrography were consistent with a mechanism involving phase separation of TMPTA during polymerization. Probable composition of the phases is discussed.
Sorption and permeation of iodine in water‐swollen poly(vinyl alcohol) membranes and iodine complex formation
Authors: Kojima Yoshitsugu , Furuhata Ken‐Ichi , Miyasaka Keizo
Published: April 2003

The sorption and the permeation of iodine in water‐swollen poly(vinyl alcohol) (PVA) membranes and the formation of PVA–iodine complexes were studied. The logarithms of the permeability and the diffusion coefficient decreased approximately linearly with the increase in polymer volume fraction. When the membrane was soaked in an aqueous I2–KI solution, it contracted and Young's modulus increased. These findings were explained in terms of the formation of extra junction points due to the PVA–iodine complexes. These changes were reversible and could be recovered by replacing the solution with water. The length of the polyiodine chain increased with the increase in the degree of hydration of the membrane. At a fixed degree of hydration, Young's modulus of an iodine‐sorbed membrane was much greater than that of a membrane soaked in pure water. This finding was explained on the basis of a double‐network structure. The extension of the membrane promoted the complex formation, and the complex disappeared when the tension was released. The critical strain necessary for the complex formation was independent of the degree of hydration. The length of polyiodine chain increased with strain and became constant at higher strains.
Adiabatic photopolymerization of acrylamide
Authors: Rodriguez Ferdinand , Chu Connie H. , Chu W. T. Wayne K. , Rondinella Mary Ann
Published: April 2003

Although the adiabatic polymerization of acrylamide using photoinitiation was first described over 30 years ago, it still offers convenient opportunities for innovation. In the present work, the effect of EDTA (ethylenediaminetetraacetic acid, tetrasodium salt) as a reducing agent with two photosensitizers is described. With riboflavin‐5'‐phosphate sodium, the rate of polymerization rises with the ⅓ power of the EDTA concentration. With a new photosensitizer, 4‐benzoyl‐N,N,N‐trimethylbenzenemethanaminium chloride, the rate rises with the ½ power of the EDTA concentration. Adiabatic temperature rise is used as the measure of conversion in the early stages of polymerization.
A scheme to predict the morphology of diblock copolymers and their blends
Authors: Hsiue Ging‐Ho , Shih Solomon Weng Feng
Published: April 2003

Diblock copolymers of α‐methylstyrene and isoprene were synthesized anionically. The morphology of the copolymers and of their blends with the homopolymers was studied by transmission electron microscopy. Based on this, a scheme is proposed to predict the morphological behavior associated with the blending of block copolymers with homopolymers. Two blending systems are discussed. They are (i) copolymer AB with homopolymers A and B and (ii) copolymers AB of two different molecular weights with homopolymer A. Two factors are considered to be the most crucial. One is the morphology of the predominant polymer (50 wt %), and the other is the weight ratio of the blends. The solubilizing effect of the block copolymer AB in the blend must also be taken into account. When the two copolymers are blended, the one with lower molecular weight was emulsified by higher one and restricted around the longer chain. It is shown that the present scheme is successful in predicting the morphology of diblock copolymers and their blends.
Effect of catalysts on the reaction between a cycloaliphatic diisocyanate (H‐MDI) and n‐butanol
Authors: Yilgör Ískender , McGrath James E.
Published: April 2003

Kinetics of the reaction between bis(4‐isocyanatocyclohexyl)methane, H‐MDI, and n‐butanol was studied in toluene at 100°C. Effects of various catalysts, such as Hg(CH3COO)2, Zn(CH3COO)2 · 2H2O, SnCl4 · 5H2O, and dibutyltindilaurate on the reaction rate and kinetics were also investigated. Reactions were followed by determining the unreacted isocyanate as a function of reaction time, using the standard dibutylamine back titration method. All catalysts seem to be very effective in increasing of the rate of the reaction compared to the uncatalyzed system. Depending on the initial stoichiometric ratio of (NCO) and (OH) and the concentration of the catalyst used, it seems possible to have preferential catalysis of the primary reaction between (NCO) and (OH) over the side reactions.
The effects of 3‐MeV proton radiation on an aromatic polysulfone
Authors: Coulter Daniel R. , Smith Mark V. , Tsay Fun‐Dow , Gupta Amitava , Fornes R. E.
Published: April 2003

3‐MeV proton beam irradiation studies have been carried out on a commercial aromatic polysulfone (Udell 1700). Physical and mechanical property changes have been monitored as a function of dose. Chemical and spectroscopic analyses have also been performed on the irradiated samples. Results have been compared to those from previous studies with electrons and γ‐radiation. A mechanism of proton‐induced degradation is proposed.
Block copolymers of n‐propyl p‐styrene sulfonate with isoprene and styrene: Synthesis, characterization, and phase separation behavior
Authors: Whicher S. J. , Brash J. L.
Published: April 2003

A series of ABA block copolymers based on n‐propyl p‐styrene sulfonate (A block) and isoprene or styrene (B block) were synthesized and characterized. The synthesis was based on methods developed previously for the anionic polymerization of n‐propyl p‐styrene sulfonate [S. J. Whicher and J. L. Brash, J. Polym. Sci., Polym. Chem. Ed., 19, 1995 (1981)], and consisted of forming a polyisopryl dianion by initiation with sodium naphthalene in THF at 0°C. n‐Propyl p‐styrene sulfonate was then added and propagated at −94°C. As was the case for n‐propyl p‐styrene sulfonate alone, it was found that only limited chain growth of this monomer initiated by living polyisoprene was possible, resulting in maximum A block molecular weights of about 10,000. The phase separation behavior of copolymers having a range of composition, as well as that of a blend of polyisoprene and poly(n‐propyl p‐styrene sulfonate) was investigated by examining thin films in the electron microscope. In the copolymers, phase separation was observed with transmission EM when THF was used as the solvent for film casting. Domain morphology was as expected for the various copolymer compositions. When films were cast from chloroform, phase separation was minimal, although it could be improved by annealing. Annealing produced relatively diffuse intermixed domains which occasionally formed unusual triangular patterns. Phase separation of the blend of homopolymers gave domains that were large enough to be mapped with SEM using both secondary electron and EDXA detectors.
Degradation of poly(vinyl alcohol) in strongly alkaline solutions of hydrogen peroxide
Authors: Hebeish A. , Abdel‐Gawad Ib. Ib. , Basily Is. K. , El‐Bazza S.
Published: April 2003

The action of hydrogen peroxide and sodium hydroxide independently as well as in combination together with stabilizer formulation–consisting of magnesium sulphate (5 g/L), ethylenediamine tetraacetic acid (2 g/L), gluconic acid (2 g/L), and nonionic/anionic wetting agent (1.5 g/L)–on poly(vinyl alcohol) (PVA) was investigated at 30°C and 95°C. The effect of sodium hydroxide (5–25 g/L) alone was to bring about an enhancement in the viscosity of PVA most probably due to gel formation. The latter was favored at higher sodium hydroxide concentrations and longer duration (30 min) of treatment. The opposite holds true when hydrogen peroxide (35% w/v) was used alone at concentrations ranging from 2 to 20 mL/L. The viscosity of PVA decreased as the hydrogen peroxide concentration increased. Nevertheless, hydrogen peroxide alone could not cause complete dissolution of PVA even at 95°C for 30 min. On the other hand, complete dissolution of PVA could be achieved under the influence of stabilized alkaline solutions of hydrogen peroxide at 95°C in less than 10 min. It was postulated that, under the conditions used, oxidation of PVA by hydrogen peroxide prevailed over gel formation under the influence of sodium hydroxide.
Structural characteristics, rheological properties, extrusion, and melt spinning of 60/40 poly(hydroxybenzoic acid‐coethylene terephthalate) (PHB/PET)
Authors: Sugiyama Hiroshige , Lewis David N. , White James L. , Fellers John F.
Published: April 2003

The rheological properties, extrusion, and melt spinning characteristics, and concomitant morphological features of 60/40 PHB/PET aromatic copolyester have been investigated. The material flows at temperatures above 190°C, but all crystallites may not melt completely until about 250°C. The material exhibits a yield stress value in shear flow. In fact, yield stress values were measured over a range of temperature from 190 to 260°C and estimated at higher temperatures. Extrudate swell measurements were also made in the same range. Significant extrudate swell does not occur until the fluid is at a temperature where the yield stress is approximately 1/50th of its maximum value. Extrudates are fibrillar in character and exhibit significant levels of crystalline orientation. The level of crystalline orientation in melt spun fibers does not vary significantly with drawdown ratio, since it is apparently developed to near its limiting extent during its flow through the die. All of these responses are similar to those observed in melt flow/processing studies of thermotropic liquid crystalline hydroxypropylcellulose.
Processing–morphology–property relationships in epoxy resins
Authors: Mijović Jovan , Williams John G. , Donnellan Tom
Published: April 2003

An investigation was conducted into processing–morphology–property relationships of a series of epoxy resin formulations. Diglycidyl ether of bisphenol A (DGEBA) epoxy resin was cured with diethylene triamine (DETA) and 2,5‐dimethyl 2,5‐hexane diamine (DMHDA). The two systems were compared by electron microscopic investigation and thermomechanical and fracture property measurements. Transmission electron microscopy has revealed a difference in the morphology of fracture surfaces. On the other hand, thermomechanical and fracture properties of DETA‐ and DMHDA‐cured formulations were found to be very similar. Three different processing (curing) conditions were used for DMHDA‐cured formulations, without an apparent effect on their properties. The previously reported improvement in impact energy of DMHDA‐cured formulations is unfounded.
Effect of resin components on the degradation of guayule rubber
Authors: Bhowmick A. K. , Rampalli S. , McIntyre D.
Published: April 2003

All natural rubbers are likely to contain some long chain fatty acids or their esters. The individual effect of the four C18 fatty acids (stearic, oleic, linoleic, and linolenic acid) present in the guayule resin on the degradation of guayule rubber has been investigated concurrently by stress–relaxation of radiation cured rubber networks and by gel permeation chromatography studies on the raw rubber in the temperature zone 70–125°C. C18 unsaturated fatty acids enhance the degradation of rubber several fold. The rate of degradation follows the order: rubber ≤ rubber + stearic acid < rubber + oleic acid < rubber + linoleic acid < rubber + linolenic acid. The thermal degradation is slower than the thermooxidative. The rate of degradation monotonically increased with the number of conjugated double bonds and is first order with respect to acid concentration. The activation energy for the chain scission for both thermal and thermooxidative degradation has been found to be 95 ± 10 kJ/mol. The mechanism of degradation of guayule rubber in the presence of fatty acids is discussed.
Surface modification of cellulose fibers. I. Spectroscopic characterization of surface‐modified cellulose fibers and their copolymerization with styrene
Authors: Zadorecki Pawel , Flodin Per
Published: April 2003

Two coupling agents based on trichloro‐s‐triazine with different terminal unsaturated groups were synthesized in order to improve the bonding between cellulose fibers and an unsaturated polyester matrix. The products of the reactions between hydroxyl groups of cellulose and reactive species of coupling agents were analysed by Fourier‐transform infrared spectroscopy (FTIR) and by elemental microanalyses. ESCA was used for surface characterization of treated fibers. The coupling agents were found to be concentrated on the fiber surface. Polymerization of styrene was carried out in the presence of treated fibers. That the unsaturated groups of the treated fibers were able to copolymrize with styrene was shown by FTIR. Further evidence of the presence of grafted polystyrene on the surfaces of the cellulose fibers was provided by ESCA measurements.
Stress–relaxation and stress–strain behavior of poly(ethylene‐co‐vinylacetate) at varying crosslink density
Authors: Fedors R. F. , Chung S. Y. , Hong S. D.
Published: April 2003

The stress–relaxation modulus of an unfilled ethylene vinyl acetate polymer at three different degrees of crosslinking was measured at 15 temperatures over a temperature span of about 160°C. At each temperature, the time response was measured for at least 3 decades of time. From these data it was possible to construct a master curve for each degree of crosslinking. The time–temperature shift factors, aT, were found to be related to temperature by the relation log aT = −A(T–273), where the parameter A has an average value of 0.234 for the three materials.
Graft copolymerization onto rubber. VII. Graft copolymerization of methyl methacrylate onto rubber using potassium peroxydisulfate catalyzed by silver ion
Authors: Lenka Subasini , Nayak Padma L. , Das Anil P.
Published: April 2003

The graft copolymerization of methyl methacrylate onto natural rubber (NR) was carried out varying the concentration of monomer, initiator, thiourea, and silver nitrate over a wide range. The grafting reaction was temperature‐dependent. From the Arrhenius plot, the overall energy of activation was computed. A suitable reaction scheme and rate expression for the rate of polymerization was suggested.
Aromatic ionomer membranes: II. Evaluation as separators for advanced alkaline water electrolyzers
Authors: Steck A. E. , Yeager H. L. , Harris F. W. , Gupta R. K. , Eisenberg A. , Besso E.
Published: April 2003

The sorption and transport properties of newly developed aromatic carboxylate polymers have been investigated in the context of their application as membrane separators for water electrolyzers. Conductance measurements of aromatic carboxylates of various equivalent weights have been performed as a function of current density, temperature, and electrolyte environment. Results have been compared with those for Nafion 117. The sorption results in dilute and concentrated solution show large water and electrolyte uptake for the aromatic carboxylate films. Furthermore, relatively large sodium ion self‐diffusion coefficients have been found in both dilute and concentrated solution environments. The results of these measurements are characteristic of microporous films. The de conductance behavior of the aromatic carboxylate ionomers is quite different from that found for nonporous 1150 equivalent weight Nafion membranes. This difference is caused primarily by the microporous structure of the aromatic carboxylates, which results in large membrane specific conductances.
Radiation‐induced grafting of methacrylic acid onto polyurethane in the presence of solvents
Authors: Omichi H. , Stannett V. T.
Published: April 2003

The radiation‐induced grafting of methacrylic acid onto polyurethane has been carried out in the presence of solvents. The swelling of polyurethane was highest when the solubility parameter of the monomer solution was 11.0. The molecular weight of polyurethane did not change with the irradiation dose up to 30 Mrad in the absence of solvent. The irradiation in the presence of solvent, on the other hand, decreased the molecular weight. The grafting yield in CCl4, benzene, and n‐hexane decreased monotonously with the decrease in monomer concentration. The large decrease of the grafting yield in CCl4 was proved to be due to the high possibility of chain transfer to CCl4. When such solvents as water, methanol, and DMF were used, on the other hand, a maximum grafting yield was obtained when the monomer concentration was ca. 75%. The hydrogen bonding among polyurethane, methacrylic acid, and solvent was found to affect both the swelling and the grafting yield.
Dynamic mechanical properties of polymer–leather composites
Authors: Kronick Paul L. , Buechler Peter , Scholnick Frank , Artymyshyn Bohdan
Published: April 2003

The effects of polymer impregnation, moisture, and lubricant oils on the complex modulus of the grain layer of leather have been studied. The impregnated materials were prepared by introducing a mixture of polyurethane oligomer and vinyl monomers into the grain layer and polymerizing by electron‐beam irradiation. Synergism was observed in the interaction of the components of the system and analyzed in terms of the adhesion of the polymer to the collagen fibers.
Diffusion of toluene sulfonic acid in nylon film
Authors: Wirbrant Anita , Sundelöf Lars‐Olof
Published: April 2003

The permeation of p‐toluene sulfonic acid through nylon 66 film has been studied at different concentrations of sulfonic acid. The ordinary diffusion coefficient in the membrane was found to increase with increasing concentration in nylon, moderately at low concentration but very rapidly when approaching the Langmuir saturation concentration.
Mechanical properties of polymers under electron irradiation
Authors: Papazian Harold A.
Published: April 2003

The Zhurkov approach to the strength of solids has been applied to polystyrene under electron irradiation. The results indicate that Zhurkov modeling may be applied to predictions of mechanical property behavior under various electron fluxes.
Further studies on polyamides from bisacid a2
Authors: Maguire J. J. , Lenk R. S.
Published: April 2003

Earlier work on the low temperature solution polyamidation of bisacid A2 has raised a number of structural problems. Work carried out more recently showed that the problem of apparent nonisostoichiometry could be reasonably satisfactorily explained. The present paper reports the synthesis and investigates the properties of a further series of polyamides based upon Bisacid A2. More importantly, however, a detailed characterization and evaluation of the new polymers with respect to their structures is presented. This enabled us to compare the various structures in the light of the experimental evidence provided by a number of analytical and spectroscopic techniques, solution behavior, molecular weight, and thermal, morphological, and mechanical properties. Some work was also done on the effect of incorporating a small amount of a trifunctional monomer into the polyamide system.