bluuebunny/crossref_metadata_2025 huggingface dataset:
Fine structure of regenerated cellulose films as revealed by dye accessibility
Authors: Wellisch Eric , Gupta M. K. , Marker Leon , Sweeting Orville J.
Published: April 2003

We have demonstrated the utility of dyeing techniques, using Solophenyl Fast Blue Green BL, to characterize a variety of regenerated cellulosic films. Measurement of the optical density ratio and the rate and magnitude of dye uptake show that differences in structure exist in regenerated cellulose films processed under different conditions. These differences are attributed to differences in lateral order and orientation of cellulose chains and are believed similar to the so‐called skin and core observed in rayon fibers. These differences have been found related reproducibly to differences in regenerating and processing conditions. Diffusion of dye into a film is very rapid initially, slowing later to an almost constant rate, depending on the dye concentration in solution and on the type of film. A modified diffusion equation of the form In C/C0 – (1 – C/C0) = Dγ2‐tC0/Cf has been found adequate to express the non‐steady state of the observed absorption process, where C0 is the initial dye concentration of the test solution, C is the instantaneous dye concentration at time t, Cf is the dye concentration in the film, γ2 is the area of film per unit volume of dye solution, and D is the diffusion coefficient. Thus, a mathematical basis is provided for structural differentiation in cellulosic films processed in various ways. Plate‐cast viscose films appear to have a dense surface (skin) exposed to the regenerating bath and a porous surface (core) on the side touching the plate, whereas machine‐cast viscose films have a dense surface on both sides.
Latex growth
Authors: Vandegaer J. E.
Published: April 2003

A method is described for preparing a latex with a particle size larger than can be obtained by direct emulsion polymerization. It consists in growing latex particles to larger size by feeding more monomer and adjusting the emulsifier concentration in a manner which prevents both coagulation and the formation of new micelles.
Relationships between chemical structure and properties of polyether urethane sealants
Authors: Damusis A. , Ashe W. , Frisch K. C.
Published: April 2003

Stress relaxation and swelling measurements were carried out and the data used for determination of the effective crosslink densities of one‐ and two‐component urethane sealants. These crosslink densities were compared with calculated values. The results were correlated with the structure of the urethane sealants. Two sealant structures were evaluated: one based on mixtures of triol prepolymers and diol adducts, and the other on triol adducts. Both one‐ and two‐component sealants were investigated. The two‐component sealants had a tendency to be undercured even when quite effective catalysts were used. The one‐component sealants, because of moisture cure and of biuret or allophanate formation, produced in most cases a higher crosslink density than the calculated triol crosslink density. It was also observed that curing efficiencies of the two‐component sealants decreased with increasing molecular weight per crosslink. Deviations from these correlations were noted when a short poly(oxypropylene)glycol of 400 molecular weight was used for curing purposes. These anomalies were detected by stress relaxation and by swelling techniques as well as by measurement of torsional modulus. Stress relaxation studies were carried out to determine the influence of temperature, catalysts, and strain on stress decay. The results again indicated that the two‐component sealants did not cure completely, and that the type of catalyst had a significant influence on degradation of urethane sealants at elevated temperatures.
Properties of semicrystalline polyolefins. IV. Crystallization phenomena in poly‐3‐methyl‐1‐butene
Authors: Kirshenbaum I. , Feist W. C. , Isaacson R. B.
Published: April 2003

A study has been carried out of the physical and mechanical properties and crystallization behavior of poly‐3‐methyl‐1‐butene (poly‐3‐MB). The melt behavior of poly‐3‐MB was examined by means of the depolarized light intensity (DLI) technique. These birefringence studies indicated the onset of motion in the crystalline phase of poly‐3‐MB at about 100°C. (over 200°C. below the melting point). These studies also showed that limited molecular motion may occur at room temperature, i.e., about 25°C. below the glass transition temperature of poly‐3‐MB.
Fraction of effective sulfur crosslinking in polybutadiene rubber vulcanizates
Authors: Meltzer T. H. , Dermody W. J. , Tobolsky A. V.
Published: April 2003

Shear modulus measurements as a function of temperature for the high cis‐ and high trans‐isomers of 1,4‐polybutadiene, vulcanized with sulfur in amounts between 2 and 44% of the recipe, show the crosslinking efficiency of sulfur in these systems to be slightly lower than in SBR‐1000, but higher than in natural rubber. Two distinct modes of mechanical behavior are noted with these stereo regular rubbers. There is pronounced crystalline behavior at low degrees of vulcanization. After crystallinity has been destroyed by increased crosslinking, both polymers behave as typical crosslinked amorphous materials. Additional evidence is found to support the conclusion that polymer structure, as well as chemical reactivity, plays an important role in the chemistry of vulcanization.
Network characterization of silicone rubber vulcanizates. Part I. solvent, temperature, and specimen shape effects on effective crosslink density determinations
Authors: Seeley R. D.
Published: April 2003

The effective crosslink densities were determined for four silica‐filled silicone rubber vulcanizates which represent different degrees of crosslinking. The determinations were made from compression‐deflection measurements of rubber specimens at an equilibrium swelling condition. Nine solvents representing a wide range of dilatant strengths were investigated at four equilibrium temperatures (8, 23, 41, and 60°C.) for their effect on the crosslinking determinations. Specimen shape effects were also investigated. Explicit equations of state were derived empirically and were found to be similar to the well‐known Mooney‐Rivlin equation in which two independent parameters are required for the definition of a dilated rubber network.
Structure and electrical properties of poly(vinyl benzoate) monolayers
Authors: Scala Luciano C. , Handy Robert M.
Published: April 2003

The structure and electrical properties of mono‐ and multilayer poly(vinyl benzoate) (PVB) films have been studied by using the films as ultrathin insulating spacers between evaporated electrodes of Cu and Sn. PVB–stearic acid mixtures were also used. Form capacity measurements, autoradiographs, and the layering conditions it is concluded that the compacted PVB film on the aqueous subphase has an average area per monomer unit of ∼8A.2 and is composed of several superimposed layers of molecules rather than a single layer. Usually each transfer operation yielded a PVB insulating film whose average thickness was estimated to be ∼37 A. Under certain and still unknown conditions, the PVB layer appeared to separate on transfer to give an average film thickness of approximately half of this value. The dielectric constant of the PVB films at room temperature and 1 keycle/sec. was estimated to be ∼3.3, and was found to be frequency‐dependent within the measured range of 100 cycles/sec. to 20 kcycles/sec. Conduction through the metal–PVB–metal sandwiches was highly nonlinear and was believed to take place by tunneling in the thinner films (∼20 A.) and by field‐assisted thermionic emission in the thicker films (∼75 A.). Interpretation of the conduction measurements in terms of a molecular model was not possible because of the wide variations in electrical properties and lack of reproducibility.
Characterization of polypropylene according to steady‐state flow behavior
Authors: Nakajima Nobuyuki , Wong Patrick S. L.
Published: April 2003

Commercial samples of polypropylene were characterized in respect to their molecular weight and molecular weight distribution on the basis of quantitative information gained from their steady‐state flow behavior. The information obtained from this analysis was used to interpret the results of extrudate swelling, reinforcement of impact strength, and lowering of brittleness temperature. Manners of thermal and shear degradation were also studied.
Mechanical properties of crosslinked polyethylene and crosslinked ethylene–ethyl acrylate copolymers
Authors: Bonotto Sergio
Published: April 2003

Stress–strain curves at various temperatures and secant modulus vs. temperature curves were used to investigate the differences that exist between peroxide crosslinked polyethylene, and vulcanized rubber. A series of hypotheses in terms of crosslinking density and crystallinity is advanced to help visualize the differences between crosslinked polyethylene and cured rubber. The same techniques were used to investigate the nature of crosslinked ethylene–ethyl acrylate copolymers. These copolymers, being more flexible than polyethylene, appear similar to “mechanical rubber,” particularly after crosslinking. Recent experiments, however, indicate that profound differences exist. The performance of crosslinked polyethylene and of ethylene copolymers at elevated temperatures depends on crosslinking density, while at lower temperatures it is dominated by polyethylene crystalline morphology. This latter factor makes crosslinked polyethylene at ambient temperature a completely different product from vulcanized rubber. It also means that a crosslinked polyethylene will have lower crosslinking density than most rubber compositions of equivalent room temperature stiffness. A good indication of crosslinking density of crystalline polyolefins may be obtained by measuring mechanical properties such as modulus at elevated temperatures. Use of reactive co‐agents is effective in raising crosslinking density to the point where fairly good elevated temperature properties are obtained without increasing the room temperature rigidity.
Extrusion characteristics of poly(vinyl chloride)
Authors: Mayrick R. G. , Sieglaff C. L.
Published: April 2003

The general flow properties of poly(vinyl chloride) in a capillary rheometer have been compared to the flow behavior in a screw extruder. It was found that the flow behavior can be characterized by either method to within the experimental accuracy of the instruments. The viscosity of the melt in the extruder barrel was calculated from its pressure profile.
Infrared spectroscopic analysis of complex polymer systems
Authors: Sefton Michael V. , Merrill Edward W.
Published: April 2003

A procedure has been developed for the analysis of complex polymer systems, using infrared spectroscopy. Its application to the analysis of styrene–butadiene–styrene triblock copolymers hydroxylated in the solid phase by reaction with peracetic acid is described. Twenty‐two frequencies of analytical interest were found sufficient to describe the infrared spectrum of the reacted polymer and were used to estimate the concentrations of the 12 components (functional groups) found to be present. A least‐squares solution of the Lambert‐Beer law equations was used to determine the 12 concentrations of interest. The errors associated with the regression and with the uncertainties in the determination of the absorptivities were determined using model compounds with the functional groups in approximately similar environments to those found in the polymer. With this procedure, the concentrations of the major components could be determined to within ±30%, which was sufficient to determine the effects of diffusion on the solid‐phase reaction process.
Isothermal rupture characteristics of a plasticized poly(vinyl chloride) in the glass–rubber transition zone
Authors: Smoley E. M.
Published: April 2003

Constant strain‐rate uniaxial extension tests to rupture were performed at 23°C on a plasticized poly(vinyl chloride) (PVC) in the glass‐to‐rubber transition zone, Tg = −18°C, where experimental failure time tf is equal to or greater than material relaxation time τ. Range of strain rate is from 1.8 × 10−4 to 1.8 × 10−1 sec−1. The rupture characteristics in stress/strain time space are analyzed on the three coordinate planes. Time and deformation separability are examined in a nonlinear‐constitutive relation. Rupture data on the coordinate planes are described by the Bueche‐Halpin theory in which time effects are considered through a small‐deformation viscoelastic property. Fracture surface morphology and separation processes in the crack tip are related to rupture characteristics.
Effect of styrene grafting on diffusion and solubility of gases in polyethylene
Authors: Toi Keio , Igarashi Kiyoshi , Takuda Taneki
Published: April 2003

Diffusion and solubility coefficient data of gases for styrene‐grafted high‐density polyethylene obtained by γ‐irradiation are reported. Diffusion coefficients were determined by the time lag method. Solubility coefficients were determined by a new, more accurate static method. Densities and volume fractions of grafted polystyrene were calculated from the observed values of extent of grafting and density of the graft copolymer films. The solubility coefficients obey simple additivity in terms of volume fraction of side‐chain polystyrene and amorphous polyethylene. However, behavior of the diffusion coefficients is more complex. Inasmuch as diffusion is a kinetic process, it is influenced by morphology. The experimental results reported here, together with x‐ray diffraction and DSC data, provide a basis for discussing the morphology of the graft copolymers.
Preparation and properties of fibers from a crystalline polymethacrylonitrile
Authors: Miyanoki Masahiko , Joh Yasushi
Published: April 2003

Fibers from a crystalline polymethacrylonitrile were prepared by dry spinning using trifluoroacetic acid as solvent. Stretchability increased when the solvent retained in the fiber was extracted with methanol. Tensile properties are well acceptable for practical use. It is notable that the stress–strain curve for the polymethacrylonitrile (PMAN) fiber shows clear yield point even under hot‐wet condition (90°C in water). Thus, the PMAN fiber is expected to have improved “hot‐wet properties” compared with conventional acrylic fibers. From the data in the compliance and resiliency maps, the PMAN fiber is expected to be one of the most promising fibers having wool‐like properties.
Thermodynamic and mechanistic characterization of water sorption in homogeneous and asymmetric cellulose acetate membranes
Authors: Burghoff H. G. , Pusch W.
Published: April 2003

The water sorption isotherms for homogeneous and asymmetric cellulose acetate membranes have been measured at different temperatures. Subtle differences between the water sorption isotherms for asymmetric and homogeneous membranes have been interpreted by suggesting that capillary condensation contributes significantly to sorption in asymmetric membranes at high activities and also to an intriguing excess sorption observed in homogeneous membranes at intermediate activities. This model has been supported by the experimentally determined values of the enthalpy and entropy changes associated with sorption.
Initial flux decline and initial rejection increase for swollen ionic membranes
Authors: Van Der Velden P. M. , Smolders C. A.
Published: April 2003

During the initial stage of operation, membrance performance in hyperfiltration experiments will be time dependent. For swollen ionic membranes, fluxes show an initial decrease while rejections initially increase in magnitude. These phenomena, also referred to as compaction, can be described by a model proposed here in which the wet membrane thickness decreases in time as a combined response to stepwise changed process parameters pressure and concentration. The response has been described by a linear first‐order differential equation and worked out by use of known concepts of flux and rejection for swollen ionic membranes. Experimental data appear to be in good agreement with model predictions.
A world‐wide program for the continuous monitoring of solar UV radiation using poly(phenylene oxide) film, and a consideration of results
Authors: Davis A. , Deane G. H. W. , Gordon D. , Howell G. V. , Ledbury K. J.
Published: April 2003

The use of poly(phenylene oxide) film to monitor UV radiation is demonstrated, and the results from the continuous monitoring of solar UV radiation at 24 sites throughout the world are presented. The global and diffuse measurements from a temperate and from a tropical site are analyzed in detail, and the effects of season and weather conditions on the UV contribution to solar radiation and the relative importance of the diffuse and direct components of solar UV are discussed.
An analysis of unsteady one‐dimensional stretching of a viscoelastic fluid
Authors: Ting R. Y.
Published: April 2003

The time‐dependent response of a viscoelastic liquid to unsteady one‐dimensional stretching deformations was examined. Oldroyd's three‐constant model for a viscoelastic fluid was used. Two cases representing two different stretching histories were analyzed: a sine stretching pulse and a step stretching pulse. The results show that high elongational viscosity may be easily reached in both cases. As the relaxation time of the liquid becomes comparable to the pulse width, elongational viscosity increases with the increase in maximum stretching rates. Conditions to maintain high levels of elongational viscosity at a subsequently reduced stretching rate were given as functions of the relaxation time and initial stretching rates. In view of recent turbulent boundary layer data, the results were used to discuss possible explanations of turbulent drag reduction in polymer solutions. It was concluded that the basic mechanisms for drag reduction in polymer soluations. It was concluded that the basic mechanisms for drag reducation may be related to the effects of high elongational viscosity and local stabilization of small shear disturbances.
Shear degradation of polyisobutene
Authors: Abbås Kent B. , Porter Roger S.
Published: April 2003

A polyisobutene of M̄w 1.98 × 106, M̄w/M̄n 1.8, was extruded in an Instron capillary rheometer. Shear degradation occurred at high shear stresses, approaching melt fracture, and was more prominent at lower extrusion temperatures for tests at 60–140°C. The capillary was 2.0 in. long with a length/diameter ratio of 66.7 and a 90° entrance angle. Repetitive extrusions at constant shear rate caused a decrease in a molecular weight and a simultaneous narrowing of the molecular weight distribution. Extrudate expansion was measured after each successive capillary pass for tests at 80°C. Extrudate swelling correlated well with (M̄z+1) M̄z/M̄w, except for the two first passes, where melt fracture was pronounced. The correlation with equilibrium extrudate expansion was almost as good for (M̄z/M̄w)3.7 (Mill's correlation) and for M̄z+1 alone. The efficiency of bond rupture is low, with the energy required to rupture 1 mole of bonds being about 200,000 kcal at 80°C.
Polystyrene degradation in model extrusion experiments
Authors: Abbås Kent B. , Porter Roger S.
Published: April 2003

An investigation has been made of the magnitude and the source of degradation of polystyrene in model extrusion experiments. A preformed solid plug of a narrow‐distribution, high molecular weight polystyrene (M̄w = 2 × 106) was used for each experiment. The extrusions were performed with an Instron capillary rheometer at constant temperatures from 160° to 220°C. The molecular weight changes occurring in the capillary reservoir during the pass of the capillary and in the hot extrudate were evaluated. Molecular weights and distributions were obtained by gel permeation chromatography. A significant degradation was observed in the capillary reservoir. The degree of degradation was independent of polymer flow. The polystyrene near the walls reacted more extensively than that closer to the axis, but a constant degradation was observed along the axis. The molecular weight profile across the capillary reservoir was attributed to a selective thermo‐oxidative degradation (160° and 190°C). Changes in molecular weight due to mechanical degradation in the capillary were observed only at 160°C. This reaction was referred to as a mechano‐oxidative process, as no degradation could be detected in the absence of oxygen. At 160°C, selective migration of macromolecules (fractionation) during extrusion did not occur to any significant extent, nor could any thermo‐oxidative degradation of the extrudate be detected. When a small amount of antioxidant (Ionol) was added to the polystyrene, no selective degradation did occur at the walls of the capillary reservoir during extrusion at 160° and 190°C.
Studies in swelling of cotton. I. Neutral salt technique to determine the true swelling parameters in cadoxen
Authors: Achwal W. B. , Joshi S. M. , Karmakar S. R.
Published: April 2003

This paper describes the swelling of cotton fiber in cadoxen containing 4.6% cadmium (w/w) and 30% ethylenediamine (w/w). A special neutral salt technique is described involving the analysis of extract as well as mother liquor which enables the determination of mechanically held liquor and hence the values of true absorption. The percentage true weight swelling values are much lower than the percentage apparent weight swelling as measured by centrifuge technique. The effect of variation in material‐to‐liquor ratio on the true absorption of cadmium and ethylenediamine is also investigated.
An investigation of the effects of the molecular weight distribution on the sensitivity of positive electron resists
Authors: Lai Juey H. , Shepherd Lloyd
Published: April 2003

The molecular weight distribution of two grades of poly(methyl methacrylate) was determined, and the solubility of that polymer in methyl ethyl ketone–2‐propanol mixtures was studied. The effects of the molecular weight distribution of the polymer and the strength of the developing solvent on electron resist sensitivity were studied experimentally and compared with a computer model of the electron exposure process. The molecular weight and the molecular weight distribution were found to have a significant effect on the sensitivity of poly(methyl methacrylate) as an electron resist. Increased sensitivity is predicted for higher molecular weight and narrower molecular weight distribution.
On the thermal degradation of poly(vinyl chloride). IV. Initiation sites of dehydrochlorination
Authors: Abbås K. B. , Sörvik E. M.
Published: April 2003

A set of poly(vinyl chloride) samples were investigated with respect to their thermal stability. The dehydrochlorination rates were measured in nitrogen at 190°C by use of a very accurate, conductometric method. For all polymers studied, a significant molecular weight increase was observed after 0.4% conversion. With only one exception, samples exhibiting higher degradation rates showed higher absorptions (350–450 nm) after 0.4% dehydrochlorination. In addition, the relative amount of short polyene sequences was found to be higher for polymers with higher degrees of branching. The dehydrochlorination reaction was predominantly initiated at sites of internal unsaturation (allylic chlorines), but an initiation at tertiary chlorines and unstable end‐groups could not be completely omitted. Head‐to‐head units, extraneous impurities, and syndiotactic sequences were found to be of minor importance in this respect.
Electron spectroscopy for chemical analyses (ESCA)—A tool for studying treated textiles
Authors: Soignet D. M. , Berni R. J. , Benerito R. R.
Published: April 2003

Electron spectroscopy for chemical analysis (ESCA) has been successfully used to determine the location of flame‐retardant polymers or reagents and crosslinking and oil/water‐repellent reagents in relation to fiber surfaces of chemically modified cotton fabrics and cotton/polyester blends. Changes in intensity of characteristic ESCA element signals were followed as the particle size of the treated fabric varied. Dimethyloldihydroxyethyleneurea (DMDHEU) and the flame‐retardant polymer formed from tetrakis(hydroxymethyl)phosphonium chloride (Thpc) and urea penetrate and are homogeneously deposited throughout cotton fabrics. The oil/water‐repellent finish, FC‐218, and the flame retardants from the THPOH/NH3 reaction and tris(dibromopropyl) phosphate are deposited on the surfaces of both cotton and polyester fibers.
The viscosity of monomolecular melts of poly(vinyl chloride)
Authors: Lyngaae‐Jørgensen J.
Published: April 2003

PVC melts are predicted to be homogeneous with single molecules as the stable flow units (monomolecular melts) at corresponding values of high temperatures and/or high shear stresses. Under these conditions, it is found that the zero shear viscosity in simple shearing flow of rigid compounds depends on the average molecular weight by weight to the 3.5 power for molecular weights between 24,000 and 100,000. All data measured under conditions where monomolecular melts are predicted fall on a master curve of reduced viscosity versus reduced shear rate when a relaxation time proportional to η0/c2T is used. It is, therefore, concluded that monomolecular melts of PVC compounds follow the same structure–viscosity relations as found for other linear melts in viscometric flow.
Diffusion of stabilizers in polymers. III. 2,4‐dihydroxybenzophenone and 2‐hydroxy‐4‐octoxybenzophenone in polyurethanes
Authors: Hauserman R. G. , Johnson M.
Published: April 2003

The diffusion of the radioactively labeled ultraviolet stabilizers 2,4‐dihydroxybenzophenone and 2‐hydroxy‐4‐octoxybenzophenone in two linear poly(ester‐urethanes) was studied over the temperature range 36–75°C. Within this temperature range, both stabilizers diffused faster in the polyurethane which had a polyester of molecular weight 2000 in its chain rather than in the polyurethane with a polyester of molecular weight 1000 in its chain. 2,4‐Dihydroxybenzophenone diffused slightly faster than 2‐hydroxy‐4‐octoxybenzophenone in both polyurethanes. In each case, the results can be represented by an Arrhenius expression D = D0 exp (−E/RT). The values of D0 and E are discussed in terms of the size of the stabilizer molecular and the structure of the polymer.
Collagen as a biomaterial: Modulus jump and degradation of collagen gels
Authors: Zvanut Carl W. , Rodriguez Ferdinand
Published: April 2003

The effect of temperature on the storage modulus G′ of UV crosslinked collagen has been investigated. Collagen solutions, 0.5%, at pH 2.2 were irradiated at 4°C to a maximum modulus, after which they were stored at 4°C. In order to study the effect of temperatures above 4°C, the gels were placed in a constant‐temperature bath and the change in modulus with time was recorded using a torsion pendulum. The temperatures studied ranged from 25° to 60°C. The results show an initial jump in modulus immediately on heating presumably due to the helix‐coil transition. The modulus goes through a maximum value. There is then a decay of modulus with time which is linear on a semilog plot. This could indicate a first‐order chain‐scission reaction, since the storage modulus is directly proportional to the number of crosslinks. A simple kinetic expression can be written for which the value of the rate constant can be determined from the data.
Diffusion in aqueous polymer solutions
Authors: Farag A. A. , Farag H. A. , Sedahmed G. H. , El‐Nagawy A. F.
Published: April 2003

The diffusion of Direct Blue 76 dye in aqueous dilute polymer solutions was studied using the capillary method. The polymer systems studied included dilute solution of carboxymethyl cellulose, poly(ethylene oxide), and polyacrylamide. It was found that the diffusion coefficient of Direct Blue 76 in carboxymethyl cellulose is higher than that in pure water, while in polyacrylamide and poly(ethylene oxide) solutions the value is lower than that in pure water. The diffusion coefficient of Direct Blue was found to decrease with increasing polymer concentration in case of poly(ethylene oxide) and polyacrylamide, while in case of carboxymethyl cellulose the diffusion coefficient increases with polymer concentration. The effect of temperature on the diffusion coefficient of Direct Blue 76 in the three polymers was found to obey the Arrhenius equation. The activation energy for diffusion of Direct Blue 76 in water, poly(ethylene oxide), polyacrylamide, and carboxymethyl cellulose was found to be 4.38, 7.7, 5.44, and 5 kcal, respectively, for polymer concentration of 0.25 g/l.
Water‐soluble polymers as retention aids in a model papermaking system. IV. Some block and graft copolymers
Authors: Howard G. J. , Hudson F. Lyth , West Jeremy
Published: April 2003

In an attempt to relate the retention behavior of water‐soluble polymers in paper formation from cellulose fibers and titanium dioxide, several copolymer types were synthesized. These were acrylamide–acrylonitrile random copolymers; block copolymers of acrylamide, acrylonitrile, and 2‐vinylpyridine with poly(ethylene oxide); and acrylamide graft copolymers of ethyl hydroxyethyl cellulose. Good retention and heteroflocculation behavior is shown only by the first of the above types of copolymers. Generally speaking, block copolymeric structures synthesized were of molecular size too small to act as good retention aids, although in a number of cases their performance was noticeably superior to that of the homopolymer analog. Adsorption isotherms are also reported and the overall results discussed in terms of a polymer bridging mechanism of heteroflocculation.
Chemorheological studies on polymer degradation
Authors: Murakami Kenkichi , Takasugi Sumio
Published: April 2003

The degradation of dicumyl peroxide‐cured natural rubber was studied by the stress relaxation method. Experiments were carried out in air, in nitrogen, and by irradiation of UV light in the temperature range of 30–200°C. We attempted to divide factors of the degradation into two parts: that caused by heat and that by light, and to study the respective degradation quantitatively. The degradation caused by UV light in nitrogen was almost independent of temperature. However, the degradation caused by UV light in air increased with temperature and the rate of degradation caused by the interaction between light and oxygen was greater at high temperature than at low temperature. It was found that scission along main chains occurs for dicumyl peroxide‐cured natural rubber by photo‐oxidation as well as thermal oxidation.
Gel permeation chromatography in the study of the molecular weight distribution of the copolymer vinyl chloride–vinyl acetate
Authors: Janča J. , Kolínský M.
Published: April 2003

A sample of the commercial copolymer vinyl chloride–vinyl acetate was fractionated by the GPC method in the preparative scale. The fractions thus obtained were characterized by light scattering, viscometry, GPC in the analytical scale, chemical analysis, and IR spectroscopy. They were compared with those obtained by precipitation fractionation. The M̄w and [η] values from the light scattering and viscometry of fractions of the commercial copolymer were employed for the calculation of the Mark‐Houwink equation valid in THF at 25°C for a copolymer with vinyl acetate content of 10–13%. Universal calibration of the [η]·M type was confirmed experimentally for the above polymer. Effects which could change the correct interpretation of the GPC data were discussed in detail. Correct interpretation of the GPC data showed an agreement between the GPC, light scattering, and viscometric data within 6–7%.
Cationic polymerization of β‐pinene and styrene
Authors: Snyder Charles , McIver William , Sheffer Howard
Published: April 2003

The yield, composition, and molecular weight of homopolymers and copolymers of β‐pinene and styrene are described as a function of the feed, temperature, and solvent. Fractionation, gel permeation chromatography, and nuclear magnetic resonance spectroscopy of GPC fractions are used as analytical tools to present evidence for copolymerization in methylene dichloride. Additional support for copolymerization is obtained from the relation of polymer composition to percent conversion. The reduction of molecular weights of homopolymers by aromatic solvents was investigated.
Filler structure and tensile properties of starch xanthide‐reinforced vulcanizates
Authors: Dennenberg R. J. , Buchanan R. A. , Bagley E. B.
Published: April 2003

Stress–strain behavior of some starch xanthide‐ and carbon black‐reinforced styrene–butadiene elastomers was investigated as a function of filler particle size and structure. In starch xanthide systems, low strain behavior is sensitive to particle structure; high strain behavior, to particle size. Electron photomicrographs of the several starch xanthide‐reinforced vulcanizates were analyzed with reference to filler particle size and structure. These parameters were then correlated with Mooney plots of [load/λ − λ−2] versus λ−1, where λ is the strain ratio. Plots of samples containing highly structured filler particles were highly nonlinear, rising steeply as λ−1 approached unity. Samples containing nonstructured filler particles were also highly nonlinear, rising steeply as λ−1 decreased to approximately 0.4. A preliminary study of the dynamic properties of these samples, as determined in an eccentric rotating‐disk rheometer, provided little additional information.
Effect of glass reinforcement on burning rates of poly(methyl methacrylate) composite candles
Authors: Barlow Joel W.
Published: April 2003

Burning rates of glass‐reinforced poly(methyl methacrylate) candles were measured under limiting conditions using an oxygen index apparatus modified to allow weighing of the candle as it burns. The limiting oxygen index was found to increase slightly with increasing concentration of glass in the candle for all samples tested. Burning rates were found to be a function of both glass concentration and orientation with respect to the propagating flame front. The burning rates of candles constructed from randomly oriented glass mats were found to increase with mat concentration by a factor of nearly 3 as mat content was increased to 70% by volume. The burning rates of candles constructed with unidirectionally oriented fibers, parallel to the flame propagation direction, were found to decrease by a factor of 2 as the glass concentration increased to 40% by volume. Erratic burning rates were observed for candles constructed with oriented fibers perpendicular to the flame propagation direction. These results are correlated by extension of existing thermally thin flame spread theories through consideration of composite solid‐state energetics and the relative tendencies of the glass reinforcements to act as wicks for supplying the flame with degraded polymer liquid.
Graft polymerization of styrene onto starch by simultaneous cobalt‐60 irradiation
Authors: Fanta George F. , Burr Robert C. , Doane W. M. , Russell C. R.
Published: April 2003

Starch‐g‐polystyrene copolymers have been prepared by the simultaneous 60Co‐irradiation of starch–styrene mixtures, and copolymers have been characterized with respect to weight per cent polystyrene (% add‐on) and also the molecular weight and molecular weight distribution of polystyrene grafts. In a typical polymerization, 4 g each of starch and styrene were blended with 1 ml water and 1.5 ml of an organic solvent; the resulting semisolid paste was irradiated to a total dose of 1 Mrad. With ethylene glycol, acetonitrile, ethanol, methanol, acetone, and dimethylformamide as the organic solvent, values for % add‐on ranged from 24% to 29%. The highest % add‐on (43%) and the highest conversion of styrene to grafted polymer (76%) were obtained when the organic solvent was omitted, and water alone was used. When water was also omitted, polymerization of styrene was negligible; however, graft copolymer was formed in the absence of water when either ethylene glycol or ethanol was added. Attempts were unsuccessful to achieve a % add‐on greater than 43% by doubling the amount of styrene in the polymerization recipe. Mixtures of equal weights of starch and styrene are relatively nonvicious, but these mixtures thicken when either water or ethylene glycol is blended in. Reasons for this thickening action and the possible influence of thickening on the graft polymerization reaction were explored.
Chemical modification of wool in aprotic swelling media
Authors: Koenig N. H.
Published: April 2003

A limited number of polar, nonhydroxylic organic liquids are suitable swelling media for chemical modification of wool. An effective medium for acylating‐type internal modification should have low molecular weight, should lack active hydrogen atoms, be highly polar, swell wool fibers, have a high boiling point, and exert a catalytic effect. Rates of modification by phenyl isocyanate, myristoyl chloride, and dodecenylsuccinic anhydride in different media decrease in the order dimethyl sulfoxide > dimethylformamide > 1‐methyl‐2‐pyrrolidinone > 4‐butyrolactone. Nevertheless, equal maximum uptake of a given reagent in these varied media is evidence of internal chemical modification. Further examples of modifying reagents are phenyl isothiocyanate, benzyl chlorides, and α‐haloketones. Supercontraction and single‐fiber stress‐strain data indicate crosslinking by bifunctional isocyanates and acid chlorides.
Diffusion of radioactively tagged penetrants through random and block styrene–butadiene copolymers and filled cis‐polybutadiene
Authors: Rhee Chong‐Kon , Ferry John D.
Published: April 2003

The diffusion of radioactively tagged n‐hexadecane in trace amounts has been studied in 22 random styrene–butadiene (SBR) copolymers with different styrene contents and butadiene microstructures; in several SBR block copolymers with different average block lengths (also diffusion of tagged 1,1‐diphenyl ethane); in a triblock SBR copolymer cast from different solvents and also molded at elevated temperature; and in cis‐polybutadiene filled to different extents with carbon black, calcium carbonate, and microglass spheres. The diffusion coefficient in random SBR copolymers decreased with increasing content of styrene and/or vinyl configuration and could be correlated with fractional free volume on the basis of linear additivity of the cis, trans, vinyl, and styrene moieties. In SBR block copolymers, the diffusion coefficient increased with increasing average block sequence length. For the triblock copolymer, the diffusion coefficient was approximately the same for samples molded or cast from solvents which are good for polybutadiene, but was far smaller for a sample cast from ethyl acetate, in which the polystyrene domains are probably lamellar. The effect of fillers on diffusion in cis‐polybutadiene was compared with calculations on the basis of several theoretical models.
The xanthate method of grafting. V. Graftability of mechanical pulp
Authors: Hornof V. , Kokta B. V. , Valade J. L.
Published: April 2003

Softwood mechanical pulp was copolymerized with acrylonitrile using the xanthate redox grafting process. Experiments carried out under different reaction conditions (temperature, H2O2, concentration, pH, reaction time) showed that mechanical pulp is less apt to form graft copolymers than chemical pulps. In most cases, long inhibition periods were observed, and the product formed thereafter contained large quantities of homopolymer. It was not possible to raise grafting efficiency by increasing the concentration of hydrogen peroxide. A series of experiments with pulps having different particle size showed a moderate increase in total conversation to polymer with decreasing mean fiber length. The latter, however, produced little influence on the copolymer/homopolymer ratio.
Studies on melt spinning. VII. Elongational viscosity and fiber morphology of multiphase polymer systems
Authors: Kim Young Woo , Han Chang Dae
Published: April 2003

Melt spinning experiments were carried out to investigate the elongational behavior and fiber morphology of multiphase polymer systems. Materials chosen for study were blends of calcium carbonate‐filled polypropylene with general‐purpose polystyrene and blends of calcium carbonate‐filled polypropylene with high‐impact polystyrene. The former is a three‐phase system in which the CaCO3 particles are dispersed, and the latter is a four‐phase system in which CaCO3 particles are dispersed, together with rubbery butadiene particles. Note that polypropylene is incompatible with the matrix of high‐impact polystyrene. The experimental technique described in part I of this series was used to determine the elongational viscosity. With the four‐phase system, the apparent elongational viscosity tends to increase as the stretch ratio is increased above a certain critical value which appears to be ca. 25. This transition does not occur with the three‐phase system and is attributable to elongation of the suspended rubber particles. The addition of small amounts of HIPS to PP‐CaCO3 increases spinnability in general, whereas larger amounts decrease spinnability.
Melting and glass transition of radiation‐induced graft polyethylene
Authors: Toi Keio , Kikuchi Midori , Tokuda Taneki
Published: April 2003

Melting and glass transition data are reported employing DSC for styrene‐grafted high‐density polyethylene obtained by γ radiation. Judging from the data of the melting point and the heat of fusion, the grafted polystyrene had no effect on the polyethylene crystallites, but the half‐width of the thermogram was observed to increase slightly, showing an effect on the crystallite size distribution. As no effect was observed on the glass transition temperature by grafting, the amorphous region of the polyethylene apparently was not affected. It is suggested, therefore, that the free volume or segmental mobility will not be decreased by radiation‐induced grafting. Very few but long grafted chains had negligible effect on the average polyethylene chain length available for segmental motion, and grafted polystyrene should be expected to differ little from the styrene homopolymer in thermal motions.
Dynamic deposition of polyacids on porous membrane supports
Authors: Ozari Y. , Tanny G. , Jagur‐Grodzinski J.
Published: April 2003

Poly(acrylic acids), poly(styrenesulfonic acid), and their block and random copolymers were tested for their ability to form dynamic membranes on partially cured asymmetric cellulose acetate. Chemically modified porous polypropylene (Celgard) was also used as a support for poly(acrylic acid). Salt rejections, water fluxes, and streaming potentials of membranes were tested under hyperfiltration conditions. Sorption of the polyelectrolytes by the cellulose acetate supports was studied using spectrophotometric, 22Na tracer, and electron microscopy techniques. The dynamic membrane formation was noted only for poly(acrylic acid) and for its 1:4:1 block copolymer with poly(styrenesulfonic acid). The uneffectiveness of other polyelectrolytes was discussed in terms of a negative zeta potential of cellulose acetate. The increase in salt rejection (R) due to the polyelectrolyte is strongly dependent on the initial Ri of the support. Sharp maxima in the ΔR ‐versus‐Ri curves have been noted for Ri in the range of 40–55%. The most significant improvement in the hyperfiltration characteristics of cellulose acetate was attained with the 1:4:1 block copolymer. Flux of 17 gfd at 350 psi and R = 93% was obtained in short‐term tests for a 0.1N feed solution. Long‐term tests did not reveal any flux or salt rejection decline for membranes in which poly(acrylic acid) was complexed with phosphoramidic groups grafted onto Celgard.
Carbon‐13 NMR of hydroxyethylcellulose: An accurate method for structural determination
Authors: DeMember John R. , Taylor Lloyd D. , Trummer Steven , Rubin Leon E. , Chiklis Charles K.
Published: April 2003

The high‐resolution carbon‐13 NMR spectrum of hydroxyethylcellulose (HEC) with about 2.5 moles of ethylene oxide (MS 2.5) average substitution per anhydroglucose ring (AHG) is presented. From models, the CMR chemical shifts for all of the different carbon atoms are assigned. Direct measurement of the relative intensities of the CMR signals for certain carbon atoms in HEC permits rapid and accurate computation of (1) the average chain length of poly(ethylene oxide); (2) the degree of substitution of ethylene oxide, and (3) the average relative degree of substitution of the alcohol groups on the AHG ring.
The influence of molecular weight on the large deformation behavior of SBS triblock copolymer elastomers
Authors: Chen Y.‐D. M. , Cohen R. E.
Published: April 2003

Engineering stress–strain properties were determined for two polystyrene–polybutadiene–polystyrene (SBS) triblock copolymer elastomers, one consisting of blocks of molecular weight 7000/43000/7000 and the other, 16000/85000/17000. In addition, various blends of these two materials were prepared in order to vary the number‐average molecular weight of the blocks in a systematic way while maintaining polystyrene content in the range of 25–28 wt %. Samples were solvent cast from benzene or benzene/heptane mixtures and annealed before testing. Ring specimens were extended to rupture at varying strain rates on an Instron tensile tester. Results indicate that number‐average molecular weight has a marked influence on stress–strain behavior over the range of molecular weights and testing conditions employed. The observed behavior is consistent with a systematic increase in the proportion of a mixed interfacial region between the pure polystyrene and polybutadiene domain as molecular weight decreases. The interfacial region contributes to mechanical hystersis, rate sensitivity, and toughness in the SBS materials. Scanning electron photomicrographs of fracture surfaces also showed systematic changes with molecular weight.
Preparation of mercaptoethylated graft fibers for adsorption of heavy metal ions
Authors: Hayakawa Kiyoshi , Yamakita Hiromi
Published: April 2003

Various kinds of mercaptoethylated graft fibers were prepared and the abilities to adsorb the heavy metal ions were studied. 2‐Hydroxyethyl acrylate, 2‐hydroxyethyl methacrylate, and vinyl acetate were graft‐copolymerized by irradiation onto five kinds of synthetic fibers and two kinds of foam polymers. Preirradiation at low temperature was far more effective for grafting than simultaneous irradiation. The mercaptoethylation was carried out in the solution or in the vapor of ethylene sulfide onto the graft fibers treated with alkali. The mercaptoethylated graft fibers showed particular affinity for Hg and Ag ions. A few of the adsorption phenomena were pursued by flow experiment of the ionic solution through a column. The preliminary reduction of the mercaptoethylated graft fibers enhanced the capacity of adsorbing to three times that of the unreduced fibers. Effects of flow rate, pH, temperature, and concentration of Hg ion on the integrated adsorbed amount were also investigated.