bluuebunny/crossref_metadata_2025_split huggingface dataset:
Graft copolymerization of vinyl monomers on modified cotton. IV. Ceric‐induced grafting on vinyl monomers on cellulose bearing different substituents
Authors: Hebeish A. , Kantouch A. , El‐Rafie M. H. 
Published: April 2003

AbstractThe influence of introducing various functional groups into the cellulose molecule on its susceptibility toward grafting with vinyl monomers such as acrylonitrile and methyl methacrylate using the Ce(IV)–cellulose redox system was studied. While cellulose bearing either cyanoethyl or carboxymethyl groups showed higher graft yields, cellulose bearing both groups showed lower yields. Presence of acrylamidomethyl groups in the cellulose molecule reduced its reactivity to grafting. The same holds true for cellulose bearing acrylamidomethyl groups along with carboxymethyl groups. On the other hand, introducing carbamoylethyl groups in the cellulose molecule enhances significantly the susceptibility of cellulose toward grafting. This is also observed with cellulose bearing cyanoethyl and carboxyethyl groups. Treating cellulose with N‐methylolacrylamide in alkaline medium seems to produce a crosslinked cellulose with lower reactivity to grafting. The results obtained with the different substrates were discussed on the basis of the change in the physical and/or chemical structure of cellulose brought about during its modification as well as on the nature of the substituent groups introduced. The mode of Ce(IV) attack on cellulose was also clarified.
The development of the velocity field in polymer melts in a reservoir approaching a capillary die
Authors: Ballenger Timothy F. , White James L. 
Published: April 2003

AbstractColor motion pictures have been made of the flow of low‐density polyethylene, polystyrene, and isotactic polypropylene at 180°C in the reservoir approach to a capillary extrusion rheometer. Detailed observations of the variation of flow patterns with extrusion rate were made. At low flow rates, essentially radial flow into the capillary entrance was observed in all polymers. With increasing flow rate, the included entrance angle α for the polyethylene and polystyrene decreased from 180°C and a “wine glass” structured velocity field was observed with stagnant circulating regions in the corners and the melt channeling in through the wine glass to the capillary entrance. The angle α was related to entrance pressure drop Δpe and capillary wall shear stress σw data through the semilogarithmic equation

where α is in degrees; Δpe/σw is interpreted as a Weissenberg number. The breakdown of stable laminar flow of the melts in the reservoir and the distortion of extrudates was observed. These phenomena seemed to be initiated by the formation of a spiralling motion in the reservoir.
Viscous behavior of some liquid rubber resins
Authors: Peyser Y. , Dealy J. M. , Kamal M. R. 
Published: April 2003

AbstractThe flow behavior of several low molecular weight polymers has been studied as a function of shear rate and temperature. These polymers, which had terminating hydroxyl or bromine groups, included homopolymers of polybutadiene and acrylonitrile–butadiene and styrene–butadiene copolymers. Viscosity was measured as a function of shear rate for the temperature range 25°–35°C, and the limiting zero shear viscosities were obtained for the range 25°–60°C. A cone plate viscometer was employed to measure the effect of shear rate on viscosity, and a Brookfield viscometer was used to verify the zero‐shear rate values. A tendency of the fluid to flow out of the cone‐plate gap was observed for some of the materials studied. From the viscosity data, characteristic times were estimated, and the data were compared with two constitutive equations. A modified Arrhenius equation was fitted to the zero‐shear viscosity data. In the case of one material, it was possible to test the Nakajima relationship between viscosity and molecular weight distribution. The dependence of material parameters on temperature is discussed in detail.
Microelectrophoresis and electron‐microscope studies with polymeric flocculants
Authors: Ries Herman E. , Meyers Bernard L. 
Published: April 2003

AbstractMechanisms for the stabilization and flocculation of colloids have been indicated by microelectrophoresis measurements and electron‐microscope observations with model colloids and polymeric flocculants. Zeta‐potential (ζ) changes and details of floc structure were observed with silica and polystyrene latex colloids. Bridging fibers of polyamine‐type flocculants appear to extend radially from the colloidal particles and vary in thickness from 20 to 300 Å. Charge neutralization and bridging may function simultaneously. Incremental additions of cationic flocculants produce gradual reduction in the negative ζ, and maximum flocculation is observed near zero ζ. Subsequent addition of flocculant reverses the potential and finally effects redispersion of the colloid. If incipient charge reversal is produced with a relatively low molecular weight cationic polymer, large flocs may then be formed on the addition of a high molecular weight anionic flocculant. Direct addition of an anionic polymeric flocculant to a negatively charged colloid may raise the negative ζ to a surprisingly high value and may thus effect stabilization instead of flocculation of the colloid.
Formation of 2,4‐dinitrophenylhydrazone on surface zone of polystyrene film irradiated by ultraviolet light. I. Effects on formation of 2,4‐dinitrophenylhydrazone
Authors: Kato Koichiro 
Published: April 2003

AbstractThe hydrazones of the acetophenone‐type 2,4‐dinitrophenyihydrazone, formed by the reaction between 2,4‐dinitrophenylhydrazine and carbonyl groups, was formed on the surface zone of irradiated polystyrene film. The changes in the amount of hydrazones formed on the films were inferred by comparing the absorptions in the ultraviolet and infrared spectra. The amounts of hydrazones formed increased with increase in irradiation time within about 3 hr and approached an asymptote with increase in irradiation time upward of about 4 hr. For the samples irradiated for 6 1/2 hr, the changes in the absorptions of the hydrazones stopped in about 3 min after the films were immersed in the 2,4‐dinitrophenylhydrazine solution, the amounts of hydrazones formed increased with increase in the amount of benzene in the 2,4‐dinitrophenylhydrazine solutions, the amounts of hydrazones formed slightly increased with rising temperature below 60°C in the solutions, and the rate of increase slightly increased with rise in temperature above 60°C in the solutions.
Melting of drawn polyethylene films
Authors: Clough S. B. 
Published: April 2003

AbstractIf drawn, crosslinked, high molecular weight polyethylene films are restrained during melting, two endothermic peaks may be noted on a scanning calorimeter. In x‐ray diffraction experiments, the appearance of a single new peak accompanies the disappearance of the orthorhombic pattern. The new peak is thought to be due to hexagonal chain packing above the melting temperature. The results are interpreted in terms of a small amount of fibrillar crystals in the drawn films.
Flammability characteristics of cotton and polyester fibers
Authors: Stepniczka H. , Dipietro J. 
Published: April 2003

AbstractThis study was undertaken to measure quantitatively the flammability characteristics of cotton and polyester fibers. The smoke density generated during the burning of these fabrics was also studied at various temperature conditions. A mathematical relationship was established between the results obtained in an oxygen‐depleted atmosphere chamber and those obtained in a chamber in which there was constant replenishing of an oxygen and nitrogen atmosphere. Three commercially available flame‐retardant treatments were utilized in this study. The effect of temperature as well as the influence of fabric weight on the flammability behavior and the smoke density of these fabrics were investigated. A novel instrument built according to ASTM standards was employed throughout this study; it was found to be versatile, convenient, and highly reproducible in the generation of the data. It was found that polyester fabrics generate far more smoke than cotton fabrics without the phenomenon of afterglow. It was found also that as the temperature increases, the smoke density of cotton fabrics increases as well, but in the case of polyester fabrics the opposite relationship was obtained.
The iron salt‐catalyzed autoxidation of atactic polypropylene
Authors: Stivala S. S. , Jadrnicek B. R. , Reich L. 
Published: April 2003

AbstractThe iron‐catalyzed autoxidation of atactic polypropylene has been studied in the solid phase using infrared spectroscopy. The reaction temperature ranged from 110° to 130°C, the ferric acetylacetonate concentration varied from 0.3 × 10−7 to 90.0 × 10−7 mole per 7.5 mg atactic polypropylene, and the oxygen concentration varied from 5 to 100 vol‐%. In the region of relatively low catalyst concentrations, the maximum steady rate varied approximately first order in respect to the catalyst concentration and about zero order at relatively high values of the catalyst concentration. Linear relationships between the maximum steady rate and the oxygen concentration, for both low and high concentrations, were obtained. A general scheme and kinetic expressions derived there‐from previously reported for the uncatalyzed autoxidation of polyolefins and recently modified to account for cobalt‐catalyzed autoxidation of actactic polypropylene has been successfully applied to the experimental results.
Bisacid A2 (2,2‐diphenylolpropane dioxyacetic acid) as a constituent of crosslinked polyesters
Authors: Lenk R. S. 
Published: April 2003

AbstractThe preparation of polyester resins using Bisacid A2 as the modifying acid in systems containing maleic unsaturation is briefly described. The detailed compositions of the various resins, the yields, final acid values, and capillary melting ranges are tabulated. The preparation of resin solutions in reactive monomers (principally styrene) and the viscosities of the resulting liquid resins at various monomer contents are given. The casting of unfilled standard sheet for subsequent testing is described. The range of Barcol hardnesses of the cast cured sheets is reported.
Preparation and characterization of phosphorus‐nitrogen polymers for flameproofing cellulose. I. Polymers of THPC and amines
Authors: Kasem M. A. , Richards H. R. , Walker C. C. 
Published: April 2003

AbstractPolymers from tetrakis(hydroxymethyl)phosphonium chloride (THPC) or tris(hydroxymethyl)phosphine (THP) with ammonia show similar thermal degradation, but appear to be of different chemical structure. Solution reaction of THPC with urea or melamine or by solid‐phase reaction with urea gives products ranging from water‐soluble liquids to hard, brittle, insoluble polymers. Reaction of THPC with piperazine yields products of low thermal stability.
Crystalline character of native and chemically treated Egyptian cottons. I. Computation of crystallinity, disorder parameter, orientation factor, and spiral angle
Authors: Shenouda S. G. , Viswanathan A. 
Published: April 2003

AbstractComputer data processing and electronic monochromatization of x‐rays were employed for determining crystallinity, disorder parameter, Hermans' orientation factor, as well as DeLuca and Orr spiral angle of native, mercerized and urea‐treated cottons. The results indicate the values for the degree of crystallinity to vary significantly between ecttons. Increase in disorder on mercerization is confirmed. The effect of urea treatment is not so well defined. The differences in Hermans' x‐ray orientation factor are significant at the 1% level between cottons and at the 10% level between treatments. Besides, from a critical analysis of the values obtained, it is shown that the spiral angle φt in the method of DeLuca and Orr is probably a direct estimate of the mean inclination of the crystallites to the fiber axis, while Hermans' orientation angle β is a complex function of other parameters as well. The computer programs which could be applied to other polymers are included.
Polymerization of styrene in an electrodeless glow discharge
Authors: Yasuda H. , Lamaze C. E. 
Published: April 2003

AbstractThe polymerization (polymer deposition) rate of styrene in an electrodeless glow discharge from styrene vapor and a mixture of styrene vapor and gas (H2, He, A, and N2) was investigated. The rate of polymerization, R, was found to be independent of the discharge power. The rate of polymerization of the pure monomer was found to be proportional to the square of monomer pressure pM. The addition of gas increased the rate of polymerization depending upon the partial pressure of the gas, px, and R can be generally expressed by R = a[pM]2{1 + b[px]}. The value of b is dependent of the type of gas and follows the order of N2, > A > He > H2. The distribution of polymer deposition was found to be nearly independent of the partial pressure of the gas and of the discharge power with N2 and H2 as plasma gas; however, with He and A, the distribution is highly dependent on the partial pressure of the gas and on the discharge power. The study strongly suggests that polymerization occurs in the vapor phase and that the growing polymer radicals deposit on the surface of the discharge vessel, yielding highly crosslinked polymer deposition.
Shock pulse mitigation in various organic foams
Authors: Wasley Richard J. , Nidick Ernest J. , Valentine Robert H. , Hoge Kenneth G. 
Published: April 2003

AbstractThe mechanical behavior of three kinds of organic foams, each at two different densities, was experimentally investigated under conditions of pulsed one‐dimensional strain shock loading. The input pulse width in each experiment was nominally 0.1 μsec, and the input stress level (as referenced to quartz) was varied between 10 and 23 kbar. The materials studied were polyurethane foam at bulk densities of 0.33 and 0.21 g/cc, syntactic foam (phenolic microballoons dispersed in a resin binder) at 0.66 and 0.23 g/cc, and polystyrene bead foam at 0.091 and 0.049 g/cc. Specimen thicknesses varied between 1.0 and 6.5 mm. It was found that the pulse duration was greatly lengthened and that the peak stress was decreased (accounting for both impedance mismatch and attenuation effects) by factors of between about 8 and 500, depending upon the type of foam, its thickness, and its density.
GPC calibration for polymers of unknown composition and structure using a real‐time computer
Authors: Braun Gérard 
Published: April 2003

AbstractA computer technique ultimately yielding, from GPC data, both differential and integral molecular weight distributions of macromolecular products with unknown composition and structure has been worked out, based on a “universal” calibration method previously proposed by other authors to calculate average molecular weights. The technique involves as sole assumption the validity of the “universal” calibration for the kind of sample under investigation. The GPC output data are handled through a realtime computer program and punched on paper tape. Together with two experimental parameters of the polymer (average molecular weights, limiting flow number) and the “universal” calibration of the columns set, the tape is used as input for the off‐line programming. Examples are presented, showing the accuracy which can be expected.
Thermal analyses of polymers. VII. Calorimetric and dilatometric aspects of the glass transition
Authors: Miller Gerald W. 
Published: April 2003

AbstractFor the determination of Tg by DTA with the use of small samples, slow heating rates, and extrasensitive amplification, it can be shown that the previously reported basel ne changes for polystyrene, polychloroprene, poly(methyl methacrylate), and polycarbonate can be resolved as endotherms. Measurements with small samples more accurately determine the calorimetric changes than with large samples, even at slow heating rates. The use of large samples for DSC or DTA measurements may be the reason for apparent heating rate dependence. The measurements of this study indicate little heating rate dependence if very small samples are used. Moreover, the slower the cooling from the melt, the sharper the endotherms, indicating the importance of thermal history. The data raise the question about the validity of assuming that a baseline or abrupt change in Cp via a DTA measurement is necessarily that of a real second‐order change or Tg. Preliminary dilatometric results tend to show that the changes for polystyrene, polychloroprene, poly(methyl methacrylate), and polycarbonate may be first order at 94°C, 32°, 114°, and 156°C, respectively. Only the change at 75°C for polystyrene appears second order by volume—temperature data.
Some aspects of PVC paste rheology
Authors: Butters G. , Roberts Gillian 
Published: April 2003

AbstractUsing the Weissenberg rheogoniometer, a technique has been developed which facilitates the measurement of shear stress data and which substantially overcomes the problem of sample loss that normally occurs at high shear rates. Using this technique, the apparent viscosities of PVC pastes based upon four different PVC paste polymers plasticized with dialphyl phthalate have been determined at a number of shear rates up to 9000 sec−1 and the viscosity aging characteristics of these paste polymers have been compared. The effect of several common plasticizers upon PVC paste viscosity and viscosity aging have been studied at shear rates of the order of 10 sec−1 and 1000 sec−1.
Rheological and heat transfer aspects of the melt spinning of monofilament fibers of polyethylene and polystyrene
Authors: Acierno Domenico , Dalton J. Nelson , Rodriguez Jorge M. , White James L. 
Published: April 2003

AbstractTwo experimental studies of the melt spinning of fibers have been carried out using low‐density polyethylene and polystyrene. First, isothermal spinning experiments were carried out and the relationship between the fiber kinematics and drawdown force was studied. The data were correlated by using the following two methods: (1) the concept of a non‐Newtonian elongational viscosity and (2) a nonlinear integral theory of viscoelastic fluids. In the second experiment, the spinline temperature profile of a monofilament fiber being pulled down from a spinneret through stagnant air was measured and the heat transfer coefficient computed. A correlation between the local Nusselt number and a fiber Reynolds number was obtained. An integral boundary layer analysis of forced convection heat transfer from a descending fiber was carried out.
Properties of poly(alkylene oxide) elastomers
Authors: Hsieh H. L. , Wright R. F. 
Published: April 2003

AbstractThe catalyst comprised of triisobutylaluminum, zinc acetylacetonate, and water was used to prepare homopolymer of epichlorohydrin; copolymers of epichlorohydrin with propylene oxide, ethylene oxide, and allyl glycidyl ether; and terpolymers of epichlorohydrin, propylene oxide, and allyl glycidyl ether and of epichlorohydrin, ethylene oxide, and allyl glycidyl ether. The vulcanizates of these rubbers provide variations of stressstrain and dynamic properties, freeze point, hardness, and solvent resistance depending on the type and amount of comonomer. In general, these rubbers have excellent heat, ozone, and oxidation resistance as well as oil and solvent resistance.
Polymerization of alkylene oxides with trialkylaluminum, metal acetylacetonates, and water
Authors: Hsieh H. L. 
Published: April 2003

AbstractTrialkylaluminum and acetylacetonates of Groups II and III metals are very effective polymerization catalysts for alkylene oxides. Addition of water increased both polymerization rate and yield. Among many combinations examined, a combination of triisobutylaluminum, zinc acetylacetonate, and water is outstanding. It gives high rate, high yield, and high degree of polymerization. The mole ratio of these three components was extensively studied and shown to be less critical than for other systems. Order of addition was not important. Elastomeric products based on propylene oxide, ethylene oxide, epichlorohydrin, and allyl glycidyl ether were prepared in high yield in relatively short reaction times. Copolymerization rates for epichlorohydrin–ethylene oxide and epichlorohydrin–propylene oxide were determined and indicated that this catalyst is anionic in character. It is concluded that the bimetallic nature of this catalyst is responsible for its high reactivity, versatility and stereochemistry.
An approach to a simplified universal calibration for gel permeation chromatography
Authors: Funt B. L. , Hornof V. 
Published: April 2003

AbstractCriteria for establishing a universal GPC calibration for poly‐1,2‐butadiene on the basis of polystyrene standards are considered. The number‐average molecular weights of the two polymers are related by a linear expression on the assumption that their respective Mark‐Houwink exponents are equal. The coefficient Cn of this expression, determined from GPC and viscosity measurements, remained constant for a considerable range of molecular weights and polydispersities. The applicability of Cn beyond the interval of present measurements is considered on the basis of results in the literature. The results are comparable to those obtained from a universal calibration based on the unperturbed dimension of polymer chains, but do not agree with those obtained from a model based on extended length.
The secondary relaxation process of poly(vinyl chloride) and its derivatives
Authors: Heidingsfeld Vikter , Zelinger Jiří , Kuška Vladimír 
Published: April 2003

AbstractThe temperature dependence of the shear modulus G′ and of the damping tan δ of poly‐(vinyl chloride), poly(vinylidene chloride), copolymers of vinyl chloride–vinylidene chloride, PVC chlorinated in solution and suspension, and chlorinated polyethylene was measured. Secondary relaxation process of PVC and its derivatives are being explained as vibration of methylene groups polarized by neighboring CCl dipoles. This process, being suppressed by lowering the concentration of the methylene groups in the PVC chain (e.g., by chlorination), remains, however, unaffected by the growth of crystalline content. The achieved results show that in the α‐transition region there occurs, in accordance with Andrews' theory, a loosening of the bonds between the CCl dipoles, whereas in the β‐transition region a loosening of the weaker bonds among the dipoles of the polarized methylene.
Chemorheological study of vulcanized rubbers under mechanical stress
Authors: Kusano Takae , Suzuki Yukizi , Murakami Kenkichi 
Published: April 2003

AbstractAt lower than the glass transition temperature, the cleavage of the molecular chains of extended vulcanized rubbers will occur. The crosslinking density of vulcanized rubbers, which were placed at room temperature for about 4 hr in nitrogen atmosphere, increased about 17% after extension of 200% at −76°C. This may be due to the recombination of cleft chains, and this can be shown by the Maxwellian type of curves between crosslinking density and forced strain. Considering the decreasing proportion of crosslinking density by the radical acceptors included in the rubbers and the fact that crosslinking density increases because of recombination of cleft chains, this was attributed to the recombination of unstable chains produced by the added mechanical stimulus.