bluuebunny/crossref_metadata_2025 huggingface dataset:
High‐strength/high‐modulus fibers of p‐phenylene oxadiazole/n‐methyl hydrazide copolymers—a new class of high‐performance organic materials
Authors: Bach Hartwig C. , Dobinson Frank , Lea K. R. , Saunders J. H.
Published: April 2003

p‐Phenylene oxadiazole/N‐methyl hydrazide copolymers were prepared by polymerization of terephthalic acid, dimethyl terephthalate, and hydrazine sulfate in fuming sulfuric acid, and coagulation of the polymer was obtained in aqueous sulfuric acid. Fibers spun from these copolymers have unusually high strength and modulus, making these materials attractive for the reinforcement of articles such as tires. Yarn tenacities of 16–21 gpd and moduli of 350–450 gpd were obtained. Yarn of these copolymers showed no significant degradation under conditions to which a tire cord material is subjected in tire building and end use. In their performance in vehicle tires, tire cords were found to be competitive with other reinforcing agents such as fiber glass, steel, and commercial poly(p‐phenyleneterephthalamide).
Grafting onto polyester fibers. III. Electrokinetic properties of acrylic acid and acrylonitrile‐grafted polyester fibers in the presence of cationic dyes
Authors: Lokhande H. T. , Mody N. R. , Rao K. N. , Rao M. H.
Published: April 2003

The electrokinetic properties such as zeta potential, surface charge density, and surface conductivity of polyester fibers grafted with acrylic acid and acrylonitrile were measured when cationic dye solutions were streamed through. The presence of the cationic dyes on the surface of the fibers and their specific adsorption at the carboxylic groups in the acrylic acid graft copolymer produce lowering of zeta potential. The decrease in surface charge density as the percent graft increases is due to the decrease in surface area of the fibers due to the adsorption of the cationic dyes. The same trend is observed with acrylonitrile‐grafted fibers. The surface conductivity of the acrylonitrile‐grafted polyester fibers increases with increase in dye concentration of the streaming solution. The results for the 27.4% grafted sample differed from those of the 7.32% and 12.1% grafts, which is indicative of the formation of a three‐dimensional network causing change in both the physical structure as well as the chemical nature of the surface of the substrate.
Application of the fung equation to the constant strain rate behavior of plasticized polyvinyl chloride
Authors: Dehoff Paul H.
Published: April 2003

A quasilinear viscoelastic equation originally proposed by Fung to characterize the uniaxial viscoelastic behavior of rabbit mesentary is used in this study to characterize the viscoelastic behavior of plasticized polyvinyl chloride for strains up to 24%. An experimentally determined relaxation function is used to predict the constant strain rate behavior of plasticized polyvinyl chloride. The predictive ability of the Fung equation is also compared with the well‐known BKZ and Lianis theories. It was found that the Fung equation agrees quite closely with the BKZ and Lianis theories but that all three theories showed only moderate agreement with experiment.
Hydrophilic interpolymer membranes from crosslinked blends of poly(vinylalcohol), poly(styrene sodium sulfonate) and poly(vinyl methyl ether–alt–maleic anhydride)
Authors: Gryte Carl C. , Chen J. , Kevorkian V. , Gregor Harry P.
Published: April 2003

Interpolymer ion exchange membranes were prepared from a compatible casting solution that contained poly(styrene sodium sulfonate), poly(vinyl methyl ether–alt–maleic anhydride), and poly(vinyl alcohol). Crosslinking of the films was accomplished through the formation of ester linkages that were stable in aqueous environments. Membrane properties (water content, capacity, concentration potential, equivalent conductivity) were measured over a wide range of membrane compositions. Ultrafiltration was carried out with a feed solution that was 0.01N in KCI and 15 ppm in erythrosin. Rejection and hydraulic permeability data were reported as a function of membrane composition.
Plasma polymerization of tetrafluoroethylene
Authors: Nakajima K. , Bell A. T. , Shen M. , Millard M. M.
Published: April 2003

The plasma polymerization of C2F4 was carried out in both continuous wave and pulsed rf discharges to establish the effects of reaction conditions on the kinetics of polymer deposition and the polymer structure. ESCA spectra of the polymer show evidence for CF3, CF2, and CH2 groups. Under conditions favoring low deposition rates, the dominant functional group is CF2. At higher deposition rates the concentration of CF2 groups is reduced and a more crosslinked polymer is produced. Both polymer deposition rates and polymer structures were essentially identical when using continuous wave and pulsed rf discharges.
Phosphine‐based flame retardants for polypropylene
Authors: Savides Chris , Granzow A. , Cannelongo J. F.
Published: April 2003

Flame retardant formulations for polypropylene are described that comprise a heat‐stable phosphonium bromide or phosphine oxide, containing cyanoethyl substituents, in combination with ammonium polyphosphate. At additive levels of (20–30)%, flame‐retarded polypropylene, with an Underwriters' Laboratories UL 94 V‐0 rating is obtained with little effect on thermal and mechanical properties of the polymer. A characteristic property of this flame retardant mixture is low smoke generation during burning. Mechanism studies indicate that the organophosphorus component alone acts as an inhibitor in the gas phase, whereas the ammonium polyphosphate alone acts in the condensed phase. The synergistic effect observed by the combination of these two components is due to the formation of a phosphorus‐rich char which forms an insulating layer.
Mechanical properties of SBS block copolymers. II. Effect of structure and selective solvent casting on stress–strain properties and mechanical hysteresis
Authors: Kalfoglou Nikos K.
Published: April 2003

Near‐equilibrium stress–strain properties were obtained for poly(styrene–b–butadiene) copolymer films cast from different solvents at 35°C. The solvents used were methyl ethyl ketone and cyclohexane, selective for PS and PB, respectively, and toluene, a common solvent for both copolymer components. Tensile properties were studied at two successive loading cycles up to a maximum elongation ratio of λmax = 7.0. At constant composition, the results were interpreted on the basis of the available morphology for these systems. The effect of hard block content (35% to 45% styrene) and at constant composition (39% styrene) of block length was also examined on such properties as elasticity and mechanical hysteresis. The results indicate that at constant composition the PB block length influences elasticity and mechanical hysteresis, also that films cast from a common solvent have higher tensile strength and increased mechanical hysteresis presumably because of a more effective load transfer between phases.
The effect of casting solvent on the sorption and diffusion of water vapor in poly(γ‐methyl L‐glutamate)
Authors: Minoura Norihiko , Nakagawa Tsutomu
Published: April 2003

Water vapor permeability of poly(γ‐methyl L‐glutamate) (PMLG) membranes prepared by using dichloroethane, trifluoroacetic acid, and formic acid as solvents was studied. The membranes prepared by casting dichloroethane and trifluoroacetic acid solutions of the polymer, designated as PMLG–DCE and PMLG–TFA, respectivley, had α‐helical structures according to infrared absorption spectra, while the membranes prepared by allowing the PMLG–TFA membranes to swell in formic acid, designated as PMLG–FA, had mainly a β‐sheet structure. The amounts of water sorbed by PMLG–DCE, PMLG–TFA, and PMLG–FA increased in that order. The isotherms of PMLG–TFA and PMLG–FA were sigmoidal‐shaped isotherms, and the heat of sorption for PMLG–TFA and PMLG–FA was larger than that for PMLG–DCE, which suggested the presence of the sorption sites. The diffusion coefficients of water for PMLG–DCE increased and then decreased with increasing concentration. On the other hand, the diffusion coefficients for PMLG–TFA and PMLG–FA increased with concentration. The activation energies of diffusion for PMLG–DCE, PMLG–TFA, and PMLG–FA increased in that order. These results were discussed in connection with the molecular conformations of poly(γ‐methyl L‐glutamate) in the membranes. From these results, it is assumed that the molecular chains in the PMLG–TFA membranes are mainly in α‐helical and partly random‐coil conformations.
Effects of gamma radiation on two aromatic polysulfones. II. A comparison of irradiation at various temperatures in air‐vacuum environments
Authors: Brown J. R. , O'Donnell J. H.
Published: April 2003

The aromatic polysulfone poly(oxy‐1,4‐phenylenesulfonyl‐1,4‐phenyleneoxy‐1,4‐phenyleneiso‐propylidene‐1,4‐phenylene) (I) showed no change in flexural yield strength after doses of γ‐radiation up to 600 Mrad in vacuum at 35,80, and 125°C (Tg = 190°C)). However, the flexural strength decreased markedly with doses above 100 Mrad on irradiation in air, to 40–60% of the initial value after 200–400 Mrad, depending on the sample and the irradiation conditions. Chain crosslinking was predominant over scission for irradiation in vacuum at all temperatures; (G(X), G(S), and G(S)/G(X) increased with the irradiation temperature, but G(S)/G(X) decreased to zero above Tg. Poly(oxy‐1,4‐phenylenesulfonyl‐1,4‐phenylene) (II) behaved similarly, except that the flexural strength was found to be very dependent on the thermal treatment of the sample. This polymer showed a remarkable retention of its mechanical properties on irradiation up to 200°C (Tg = 230°C) in the absence of air, the flexural strength being retained up to 500 Mrad. Radiation annealing occurred at 35°C in vacuum and air and combined radiation and thermal annealing at 125 and 220°C. Progressive removal of surface layers from flexural test bars of I irradiated in air showed that the decrease in flexural strength with dose could be explained by a decrease in the molecular weight towards the surface resulting from radiation‐oxidation reactions.
Plasma polymerization of tetrafluoroethylene. III. Capacitive audio frequency (10 kHz) and AC discharge
Authors: Morosoff N. , Yasuda H. , Brandt E. S. , Reilley C. N.
Published: April 2003

The plasma polymerization of tetrafluoroethylene (TFE) is studied in a capacitively coupled system with internal electrodes using a 10 kHz (af) and a 60 Hz (ac) source. The emphasis is on identifying conditions that are compatible with continuous coating of plasma polymer on a substrate moving through the center of the interelectrode gap. Operation at a pressure below 100 mTorr is most favorable for deposition of a substantial portion of the plasma polymer on this substrate. Plasma polymer deposited in this way is characterized by ESCA and by deposition rate data and compared to that deposited using rf power in both capacitively and inductively coupled systems. The polymers found in all systems are broadly similar and completely different from conventional poly(TFE). The distribution of power density in the various systems has been identified and compared. This is accomplished by using the known susceptibility of fluorine‐containing polymers (including plasma polymer) to a high‐power plasma as a probe of plasma power density within the interelectrode gap in the capacitively coupled system. The most active zone of the af or ac plasma is close to the electrode at a plasma pressure of approximately 40 mTorr. The use of a magnetic field leads to an intense localized glow such that etching by active fluorine atoms occurs at a specific locus on the electrode. By contrast, the low‐pressure rf capacitively coupled glow discharge is the mildest of those investigated, and its most active zone is further from the electrode and much more diffusely localized by a magnetic field.
GPC: Use of automatic weighing to determine elution volumes
Authors: Moebus Gerhart A. , Crowther John A. , Bartick Edward G. , Johnson Julian F.
Published: April 2003

An automatic balance has been designed, constructed, and tested for continuous determination of the weight of the eluent in chromatography. This balance is considerably more precise than the frequently used automatic siphons. As the elution volume for any molecular species is independent of flow rate over a considerable range, the balance can be used with relatively inexpensive pumps, and thus highly precise constant volume pumps are not required.
Polyimide fibers: Structure and morphology
Authors: Goel R. N. , Hepworth A. , Deopura B. L. , Varma I. K. , Varma D. S.
Published: April 2003

Polyimide fibers were prepared by wet spinning of poly(p,p′ ‐diaminodiphenylmethanepyro‐mellitamic acid). Density measurements and x‐ray diffraction studies were carried out to study the structure of the resultant polyimide fibers. Polyamic acid as well as undrawn polyimide fibers were essentially amorphous with two amorphous haloes. Hot drawing of the fibers at 300°C resulted in increase in crystallinity, and a simultaneous decrease in density also took place. X‐ray data revealed that meridional reflections correspond to the repeat unit length in the fiber. Scanning electron micrography studies indicated that polyamic acid fibers prepared by a wet‐spinning technique developed voids during spinning which increased on cyclodehydration to the polyimide state. Hot drawing of fibers resulted in enlargement of these voids. However, a highly fibrillated structure was developed during drawing which could account for the strength of the fibers.
ESR studies of the photodegradation of cellulose graft copolymers
Authors: Hon David N.‐S.
Published: April 2003

Ultraviolet light induced free radicals in cellulose and cellulose graft copolymers were studied by means of ESR spectroscopy. At least six kinds of free radicals were formed in cellulose when the polymer was irradiated with ultraviolet light. Polystyrene and poly(methyl methacrylate) are more resistant to ultraviolet light than cellulose; however, the cellulose graft copolymers of polystyrene and poly(methyl methacrylate) were degraded by ultraviolet light. ESR studies revealed that photoinduced free radicals in cellulose graft copolymers were formed at the grafting branches of the copolymers rather than the cellulose backbone. The mechanisms of light stabilization and energy transfer reactions of cellulose and cellulose graft copolymers are discussed.
Impact resistance and secondary transitions
Authors: Hartmann Bruce , Lee G. F.
Published: April 2003

Instrumented Charpy impact measurements were made on polycarbonate from liquid nitrogen temperature to room temperature. The polymer had a transition from brittle fracture to ductile failure at −130°C. Scanning electron micrographs of the fracture surfaces did not correlate with the secondary transition or test temperature. A Fourier analysis of the impact pulse covers a wide range of frequencies, but the dominant frequencies at room temperature are below 200 Hz. Time–temperature superposition shows that the secondary transition occurs over a broad frequency range centered at 7 MHz at room temperature. Impact strength and the secondary transition (at impact frequency) both have a maximum value around −75°C.
Pneumacel: Basic technology and applications
Authors: Bonner W. H. , Fish F. H. , Webb M. Q.
Published: April 2003

Pneumacel, a new kind of resilient closed‐cell foam, has characteristics especially useful for firm cushioning materials. A fluorocarbon inflatant in addition to air present in the closed cells provides a mechanism for recovery from long‐term loading for nonelastomeric polymer foams such as poly(ethylene terephthalate). The basic structural features characterizing pneumacel contribute to its performance as a resilient foam. Important principles in selecting the optimum combination of polymer and inflatant are described, as well as the process for making pneumatic cellular products. Development work on applications of pneumacel fibers has led to its utilization in cushions for under carpets, padding for use over springs in mattresses, automobile seats, and furniture. Properties of the assemblies of fibers for such uses are described.
Carboxyl‐containing starch graft polymer: Preparation and use in heavy metal removal
Authors: Rayford W. E. , Wing R. E. , Doane W. M.
Published: April 2003

Water‐insoluble carboxyl‐containing starches were prepared by grafting acrylonitrile onto a highly crosslinked starch followed by base saponification to convert nitrile groups into a mixture of carboxamide and carboxylate groups. Ceric ammonium nitrate or ferrous sulfate–hydrogen peroxide was used to initiate graft polymerization of acrylonitrile. The isolated products were evaluated for the removal of Cd2+, Cu2+, and Pb2+ from aqueous solution.
Copolymerization of ethylene chlorophosphonite with 2‐phenyl‐1,3‐dioxolane and its flame‐retardant effect on polyester fabric
Authors: Inagaki Norihiro , Katsuura Kakuji
Published: April 2003

Copolymerization of ethylene chlorophosphonite (ECP) with 2‐phenyl‐1,3‐dioxolane (PhD) and the flame‐retardant effect of the copolymer on polyester fabric were investigated. (1) Copolymerization occurred without added catalyzer. The number‐average molecular weight ranged from 600 to 1000. 1H‐nmr and ir spectra for the copolymers showed that their structures varied depending on feed composition (ECP/PhD ratio): ECP/PhD less than or equal to 1 yielded an alternating copolymer having the structure
magnified image
and at ECP/PhD ratios greater than 1, some insertion reaction of ECP into polymer I occurred. (2) Selectivity of flame retardation could be observed. The copolymer with structure I was an effective flame retardant for polyester fabric but useless for cotton fabric. Its effectiveness in polyester fabric
was superior to that of TBPP.
Complex‐forming polymeric sorbents with macromolecular arrangement favorable for ion sorption
Authors: Kabanov V. A. , Efendiev A. A. , Orujev D. D.
Published: April 2003

Crosslinked polymeric sorbents with macromolecular arrangement favorable for sorption of copper ions have been obtained obtained on the base of copolymer of diethyl ester of vinylphosphonic acid with acrylic acid. The general principle involves interaction of linear polymer and sorbing ions in solution where the segments of the macromolecules are still mobile enough, subsequent fixation of optimal ion uptake conformations of macromolecules by crosslinking of metal polymer complexes, and removal of ions from crosslinked sorbent. Such treatment increases the exchange capacity of the sorbents more than twice and improves essentially its kinetic characteristics in comparison with the same copolymer crosslinked by conventional methods without special arrangement of macromolecules. The rate of the uptake on the sorbents with macromolecular arrangement favorable for ion sorption first increases with increase in the degree of crosslinking and then decreases. Apparently the jise of the crosslinking degree leads to more rigid fixation of the optimum ion uptake conformations of the macromolecules' segments. Further increase of the crosslinking degree alongside with fixation prevents ions from diffusion into the sorbent.
Polymer deposition in sisal fibers: A structural investigation
Authors: Barkakaty B. C. , Robson A.
Published: April 2003

Sisal (Agave sisalana) fibers were graft copolymerized with certain vinyl monomers (methyl acrylate, ethyl acrylate and methyl methacrylate) using gamma irradiation and ceric ammonium nitrate as initiation techniques. Examinations of the surface topology and the internal structure of the grafted fibers made by scanning electron microscopy. The results derived from the SEM observations on transverse sections of the grafted fibers were supplemented by information obtained by polarized light microscopy. Polymer was deposited not only on the surface of the fiber substrate, but also in the lumen, the middle lamellae, and throughout the cell wall network of the multicellular aggregates. The degree of polymer inclusion in the lumen (which is the most conspicuous of all the available internal sites) was found to depend on the percentage graft copolymer add‐on, as well as on the previous history of the fiber (natural or chemically modified). The mechanical properties of the grafted fibers were investigated (by means of an Instron tensile tester).
Accuracy of the parallel‐plate analogy for representation of viscous flow between coaxial cylinders
Authors: Worth R. A.
Published: April 2003

The accuracy of the parallel‐plate approximation to represent various viscous flows of non‐Newtonian fluids between coaxial cylinders is investigated. Four types of flow are considered: tangential drag flow, tangential pressure flow, and axial pressure flow. The solutions for flow between parallel plates are compared with the exact solutions, and the errors are plotted against radius ratio for a number of values of the power‐law index to provide an indication of the range of usefulness of the parallel‐plate analogy.
Kinetic studies on the condensation reaction of 2‐methylol‐4‐t‐butylphenol with 4‐t‐butylphenol using acid catalysts. I
Authors: Reddy B. Siva Rami , Rajadurai S. , Santappa M.
Published: April 2003

The rates of the individual reactions of 2‐methylol‐4‐t‐butylphenol with 4‐t‐butylphenol were measured under varying mole ratios of reactants in the presence of different acid catalysts (5.0 × 10−3 N to 2.0 × 10−4 N) at five different temperatures (60, 65, 70, 75, and 80°C). In all the experiments, the reactions were found to obey second‐order rate law. The values of the Arrhenius parameters and the entropy of activation for the overall reaction were calculated. The relative catalytic efficiencies of the acid catalysts followed the order HNO3 > HCl > H2SO4.
Gel permeation chromatography of poly(dimethyl siloxane). I. The universal calibration
Authors: Mandík Lumír , Foksová Alena , Foltyn Josef
Published: April 2003

The Benoit universal calibration method has been tested for evaluation of GPC data of polydimethylsiloxane (PDMS) in toluene at 60°C. For the conversion of the calibration curve for polystyrene to the PDMS calibration curve, the Mark–Houwink equation for PDMS in toluene at 60°C was derived: [η] = 9.77 × 10−5 M0.725. The applicability of this universal calibration was proved by the experimental results on five PDMS model samples. For the correct evaluation of the PDMS elution curve, the use of the true calibration is inevitable, because the hydrodynamic volume of PDMS molecular weight unit is somewhat different from the polystyrene one.
Statistical methods for comparing GPC curves
Authors: Füzes László
Published: April 2003

The possibilities of comparing the GPC curves of two or more polymers were studied, and the method of “distinguished points” (DPs) is suggested for this purpose. The features of these DP values as random variables were investigated. According to the experimental results they meet the requirements of the statistical tests applied in this text. In order to indicate the significant deviation or the agreement of the DP values of GPC curves of two polymers, the sequential U and t tests are suggested, because with these methods the number of the necessary parallel measurements is considerably decreased, and one can also decide on the magnitude of the variation on must be able to detect, while in the case of more than two polymers the methods of the analysis of variance can be utilized. The molecular weight ranges in which significant differences occur can also be determined. The described methods were tested by materials of known molecular weight distributions.
Polymer film‐type channel electron multipliers: Their characteristics and comparison with bulk‐type flexible multipliers
Authors: Kishimoto Yoshio , Hayashi Tomonao , Hashimoto Masashi , Ohshima Tsutomu
Published: April 2003

Polymer film‐type channel electron multipliers (CEMs) were developed and their characteristics investigated in comparison with bulk‐type flexible CEM. As film‐type CEMs, a paint‐coating‐type CEM and a solvent‐etching‐type CEM were fabricated. The paint‐coating‐type CEM is made by coating a “paint” which is prepared by dissolving in a solvent an electronically conductive polymeric composition having a high secondary electron emission yield. Up to the present study the mean gain of the film‐type CEM, in spite of the lower resistivity of the dynode, seems to be slightly more dependent on the count rate than that of the bulk‐type CEM made of the same material. However, the convenience of fabricating the dynode film by coating the dynode‐forming paint on the internal surface of any shaped tube or a flexible polymer tube would overcome the slight disadvantage mentioned above.
Flow visualization of cellulose acetate–acetone solutions
Authors: Boudreaux Edwin , Cuculo John A.
Published: April 2003

The flow behavior of four cellulose acetate–acetone solutions varying from 20.00% to 28.18% solids concentration was observed using flow visualization techniques at 24°C with an industrial‐type dry spinning system. Fibrous particulate matter entertained in the solutions and crossed polars revealed the streamlines and the birefringence due to flow in glass spinnerets. The streamlines of the four solutions were radially convergent at all obtainable throughputs. The crossed polars revealed a cone of birefringence with the order of the interference colors decreasing upstream of the capillary inlet. The intensity and extent of birefringence varied somewhat with concentration and throughput. Except for kneeing, the emerging extrudates were undeformed. The kneeing was not a result of flow instability a t the capillary inlet but was due to another, undetermined instability. A separate study of the kneeing revealed both a concentration dependence and hysteresis. The birefringence of the emerging extrudates was a function of both concentration and throughput, and it yielded some information about the structure of the solutions.
Frequency distributions of breaking load, tenacity, and ratio of cell wall thickness to ribbon width for single cotton fibers
Authors: Patel N. C. , Dweltz N. E.
Published: April 2003

Analysis of the frequency distributions of breaking load, tenacity, and ratio of cell wall thickness to ribbon width (C/R) for single cotton fibers in this study has indicated that they can all be represented by β‐distributions. This suggests that a parallel model of element configurations exists in which there is a uniform distribution of elemental strengths in single cotton fibers before as well as after slack mercerization. In the case of breaking load and tenacity, the distributions are positively skewed and the skewness decreases on slack mercerization, suggesting that quite a few potentially weak places have been either completely removed or at least strengthened. The changes in C/R ratio on slack mercerization for cottons having a range of maturity have been examined and discussed. The dependence of properties such as breaking load, tenacity, and linear density on cell wall to ribbon width ratio (C/R) have also been studied.
Influence of drawing and molecular weight on structural‐mechanical properties of acrylic fibers
Authors: Stoyanov A. I. , Kpestev V. P.
Published: April 2003

The influence of drawing and molecular weight in a narrow range on the several structural‐mechanical properties of acrylic fibers have been investigated. Drawing of fibers (λ = 3x–6,5x) leads to a considerable increase of tenacity. These data were explained with the orientation and perfection of structure. It was found that the molecular weight in closer range influences the density, perfection of structure, and the stability of fibers to repetitive deformation. The results show that the diversions of the average molecular weight, in the manufacture of commercial acrylic fibers, must be negligible.
Effect of molecular weight distribution on elongational viscosity of undiluted polymer fluids
Authors: Bersted B. H.
Published: April 2003

A combination of the Bersted model, giving the relaxation spectrum in terms of the molecular weight distribution (MWD), and the rubberlike‐liquid model of I odge is used to describe the elongational viscosity for constant extensional strain rates in terms of the MWD. Predictions of this hybrid model are in reasonable agreement with experimental results for polystyrene, if one assumes a strain rate dependent truncation of the relaxation spectrum. The predicted effects of varying molecular weight and breadth of the molecular weight distribution on the extensional viscosity are presented. At constant weight average molecular weight and constant strain, a narrower MWD is predicted to yield an extensional viscosity‐strain rate curve that is essentially shifted to higher strain rates relative to a broader MWD. Furthermore, at constant weight, average molecular weight, constant strain, and high strain rates, a narrower MWD is predicted to yield a higher extensional viscosity.
Thiuram vulcanization of natural rubber in the presence of hydrofuramide and ethanolamines
Authors: Banerjee B. , Chakravarty S. N. , Kamath B. V. , Biswas A. B.
Published: April 2003

Influence of hydrofuramide and ethanolamines on efficient vulcanization (EV), semi‐EV, and conventional sulfur vulcanization accelerated by tetramethyl thiuram disulfide is reported. In the case of thiuram vulcanization, the amines increase the cure rate but reduce the crosslink density. The interaction of tetramethyl thiuram disulfide with amines has been studied. The amines interact with thiuram disulfide (TMTD) giving rise to the formation of gaseous products. Thermogravimetric analysis shows weight loss of about 50% in case of TMTD–ethanolamine system and 25% in case of TMTD–hydrofuramide system. Gas chromatographic studies of the gaseous products indicate that it consists mainly of H2S. The other constituents in the gaseous product are CO2 and a thiol. A possible reaction based on these observations to account for decrease in crosslink density in thiuram vulcanization caused by amines is reported.
Polybutadiene adhesive compositions
Authors: Alvino William M.
Published: April 2003

This paper deals with the development of adhesives that are useful for preparing flexible laminates. The adhesive compositions are based on the chemistry of 1,2‐polybutadiene polymers and their reactions via chain extension and epoxidation. The resulting materials can be suitably formulated to produce resins that can be used to impregnate fibrous reinforcements which can be B staged; when laminated to copper, these materials give products with good peel strength, solder resistance, tear strength, and flame resistance. These adhesives can also be used to bond polyimide and polyester film to themselves and to copper. Typical properties of selected laminates include peel strength values of 8 lb/in. width, tear strength of 1–2 lb, oxygen index from 29 to 37, and excellent solder resistance.
Fractography of nylon‐6 yarn
Authors: Ogata N. , Dougasaki S. , Yoshida K.
Published: April 2003

The breaking mechanism of nylon‐6 yarn is investigated, and the breakage of the yarn under simple tensile loading conditions is compared to that of a filament caused by the same loading. The simple model yarn consisting of seven filaments was prepared for this purpose. The yarn was ruptured at a low rate of extension, and the fracture morphologies of the filaments in the yarn were inspected by a scanning electron microscopy. These morphologies are clearly different from those of the filaments broken individually under the same testing conditions used for the yarn. Various kinds of appearances are obtained in the yarn, for example, a large V‐shaped notch is observed, the controlled ductile tearing region is developed across the filament at a large angle to its axis, and the ruptured end is expanded into a plane which is perpendicular to its axis. These causes are discussed in detail to understand the breaking mechanism of the yarn.
Preparation of a flocculant based on polyamides
Authors: Mircheva V. , Mladenov I. , Konsulov V. , Sodeva D.
Published: April 2003

A flocculant based on waste oligomers from the polycaprolactam production was synthesized by alkaline reduction with Ni/Al alloy. Both the reduced oligoamide and the sodium aluminate are precipitated by methanol. An oligomer, absorbed by a mineral carrier, is isolated as final product. The modified oligoamide was characterized by elemental analysis, IR spectra, and was shown to contain hydroxyl groups. The prepared flocculant may be used for the clarification of natural dilute (1%) clay suspensions and wastewaters. It accelerates the precipitation 35 times, giving a compact precipitate, which favors the decanting of the clarified liquid. The optimal concentration of the flocculant is 1.8 g/liter (corresponding to 0.06 g/liter oligomer).
Physical and chemical properties of methyl trifluoroacrylate–α‐olefin copolymer and its hydrolyzed copolymer
Authors: Watanabe Terutaka , Matsuda Osamu , Tabata Yoneho , Machi Sueo
Published: April 2003

Physical and chemical properties of alternating copolymers of methyl α,β,β‐trifluoroacrylate (MTFA; CF2CFCO2CH3) with α‐olefins such as ethylene, propylene, and isobutylene and their hydrolyzed copolymers were investigated. The original ester‐type copolymers are amorphous and hydrophobic. The copolymers, except for the MTFA–isobutylene copolymer, were found to be easily hydrolyzed in boiled NaOH–methanol aqueous solution to give hydrophilic fluoropolymers which contain nearly theoretical amounts of carboxyl groups. No chain scission takes place during the hydrolysis. The decomposition temperature of the original ester‐type copolymers is in the range of 347° to 379°C in nitrogen atmosphere, and the glass transition temperature is in the range of 21° to 76°C. Two steps of weight decrease, at around 100°C due to the removal of absorbed water and around 250°C due to the decomposition, were observed in the TGA curve of the hydrolyzed acid‐type copolymers. Both ester‐ and acid‐type copolymers were crosslinked by electron beam irradiation, while the MTFA–isobutylene copolymer was degraded. The tensile strength of the copolymers is in the range of 190 to 450 kg/cm2.
Permeability of solutes through cellophanes grafted with vinyl monomers. I. Diffusion of potassium chloride, urea, and uric acid
Authors: Takigami Shoji , Maeda Yasukatsu , Nakamura Yoshio
Published: April 2003

The diffusive permeability of potassium chloride, urea, and uric acid through cellophanes grafted with acrylamide, acrylic acid, styrene, and N‐vinyl‐2‐pyrrolidone by γ‐ray irradiation was studied. The diffusive permeability coefficients of the permeants through the grafted cellophanes were increased with increase in hydration of the grafted membranes, except for the permeation of potassium chloride through cellophanes grafted with acrylic acid. The permeation of potassium chloride, urea, and uric acid through the various grafted cellophanes is explained by the free volume concept of homogeneously water‐swollen membranes. However, the behavior of the permeation of potassium chloride through cellophane grafted with acrylic acid deviated from that of nonionic membranes because of the contribution of the electrical interaction between electrolyte and charge of the membrane.
Permeability of solutes through cellophanes grafted with vinyl monomers. II. Diffusion of potassium chloride through cellophanes grafted with acrylic acid
Authors: Takigami Shoji , Maeda Yasukatsu , Nakamura Yoshio
Published: April 2003

The permeability behavior of potassium chloride through cellophane grafted with acrylic acid by a γ‐irradiation method was studied by the theoretical equation derived from the phenomenological equation and compared with the results of Donnan membranes equilibrium. It was shown that the permeation of potassium chloride through the grafted cellophanes exhibited behavior typical of a polyionic membrane for grafts of more than 55% but depended on the permeability of both cellophane and graft regions for lower percents of grafting. It was found that the dominant factor affecting the permeation of potassium chloride was an effective concentration of fixed charge in the membrane.
A model of physical adsorption of gases
Authors: Burghoff H.‐G. , Pusch W.
Published: April 2003

Using the Gibbs description of surfaces, a sorption model is developed which describes sorption isotherms for such systems as water in polymers. Moreover, the Freundlich isotherm for monolayer sorption is obtained. The physical interpretation of the constants of the model and the boundary conditions required for application to sorption isotherms are discussed. On basis of the Freundlich isotherm, a multilayer model is proposed to describe the water sorption in polymers. Experimental results within the whole range of relative humidity are found to be in excellent agreement with the multilayer model. Disagreement between model isotherm and experimental data of some polymers at relative humidities above 90% might be due to capillary phenomena not considered in the present model description.
Preparation of Fresnel lenses by radiation cast polymerization
Authors: Kaetsu Isao , Yoshida Kenzo , Okubo Hiroshi
Published: April 2003

Preparation of Fresnel lenses was investigated applying radiation polymerization of methyl methacrylate prepolymer systems containing polyfunctional monomers. Line focus Fresnel lenses 75 × 75 cm could be prepared in very short time cycles with sufficient exactness by radiation cast polymerization, preferably at low temperatures. Preparation of Fresnel lenses could be carried out also very easily and efficiently by printing the soft plastic prepolymer sheet with a Fresnel lenses mold and then curing it by irradiation.
Polymerization studies of creosote bush (Larrea tridentata) phenolic resin with formaldehyde
Authors: Belmares Hector , Barrera Arnoldo
Published: April 2003

About 25% of the surface area of Mexico is covered by the shrub Larrea tridentata, also known as creosote bush. Therefore, an intense study of the shrub as a source of industrial raw materials was started. Presently, we have studied the polymerization of the phenolic resin of Larrea with formaldehyde. This polymerization has been carried out in bulk and in aqueous suspension with acid catalysts such as oxalic and hydrochloric acids. The molar ratio of Larrea resin/formaldehyde was 1/1, 1/3, and 1/4 at different reaction times. Larrea resin and the formaldehyde condensation products were characterized by gel permeation chromatography (GPC), proton nuclear magnetic resonance (NMR), and vapor pressure osmometry (VPO).
Acrylic‐functional aminocarboxylic acids and derivatives as components of pressure‐sensitive adhesives
Authors: Heilmann S. M. , Smith H. K.
Published: April 2003

High‐performance thermoplastic pressure‐sensitive adhesives have been prepared by copolymerization ofN‐acryloylamino acid and acid derivatives with long‐chain alkyl acrylate esters. A comparative study with equivalent copolymers made from conventional polar comonomers and long‐chain alkyl acrylate esters has shown that theN‐acryloylamino acids and derivatives impart generally higher levels of tack, adhesion, and cohesion than their conventional counterparts.
Curing reactions in plastic prepolymers and propellants. I. Polystyrene
Authors: Kishore K. , Verneker V. R. Pai , Vasanthakumari R.
Published: April 2003

Curing reactions of the viscous PS prepolymer and PS/AP propellant slurry have been studied. The molecular weight of the binder (separated from the propellant) and the prepolymer was found to increase to a maximum value, remain constant for some time, and then fall off between 50–125°C. The molecular weight of the binder was found to be less than corresponding prepolymer between 100–150°C but at lower temperatures (50–75°C) the reverse was found to be true. The increase in the molecular weight during curing at lower temperatures has been explained on the basis of Trommsdorff effect which gets support from the estimated activation energy (9 kcal mole−1) for the curing process. Curing was recognized as chain extension where the rate of polymerization becomes diffusion controlled below 75° C.
Emulsion copolymerization of alpha‐methylstyrene and styrene
Authors: Rudin Alfred , Samanta M. C.
Published: April 2003

Fast copolymerizations of styrene and alpha‐methylstyrene can be achieved in emulsion systems where free‐radical reactions in the bulk or solution are inefficient. The Smith–Ewart–Gardon theory of emulsion polymerization was developed for homopolymerizations but should extend to this copolymerization since the particular comonomers meet the basic assumptions of this model. Sodium lauryl sulfate surfactant provided faster initial polymerization rates, but steady‐state conversions were faster with potassium laurate, especially at higher alpha‐methylstyrene contents. This is ascribed to acceleration of potassium persulfate decomposition by the former soap. Monomer concentration in the polymerizing particles was constant during steady reaction rates. The rate of volume growth of particles during this interval was generally as predicted by theory. The number of particles and particle sizes could be predicted well if allowance was made for initiator wastage reactions. The observed average number of radicals per particle appeared to be 0.5. Analysis of the composition of monomer droplets and proton NMR analyses of copolymer compositions provided independent confirmations that the present emulsion copolymerization was consistent with the terminal copolymerization model.
Synthesis of copolyamide–esters and some aspects involved in their hydrolysis by lipase
Authors: Tokiwa Y. , Suzuki T. , Ando T.
Published: April 2003

Copolyamide–esters (CPAEs) were synthesized by the amide–ester interchange reaction. The change of intrinsic viscosity during CPAE synthesis was negligible. Polyamide blocks were shortened with increasing reaction time and polyester content. The polymerization degree of nylon 12 blocks on CPAE was smaller than that of nylon 6 blocks. CPAEs were hydrolyzed by Rhizopus delemar lipase. The biodegradability decreased with the shortening of the polyamide blocks and with increasing polyamide content. It was concluded that the amount and distribution of the hydrogen bonds, based on the amide group, in the CPAE chains strongly influenced their biodegradation by this lipase.
Synthesis of cationic flocculant by radiation‐induced copolymerization of methyl chloride salt of N,N‐dimethylaminoethyl methacrylate with acrylamide in aqueous solution
Authors: Okada Toshimi , Ishigaki Isao , Suwa Takeshi , Machi Sueo
Published: April 2003

The radiation‐induced copolymerization of the methyl chloride salt of N,N‐dimethylaminoethyl methacrylate (DMAEM·MC) with acrylamide (AAm) was used to prepare a cationic polymer flocculant. The polymerization rate increased with increasing dose rate, polymerization temperature, monomer concentration and mole fraction of AAm in the monomer mixture. The molecular weight of the copolymer was also found to increase with monomer concentration and mole fraction of AAm, but at high concentration and fraction of AAm, intermolecular crosslinking tends to occur during the polymerization to form water‐insoluble copolymer. A water‐soluble copolymer having various molecular weights and cationic strengths can be synthesized by selecting suitable reaction conditions; i.e., this radiation process can provide a much higher molecular weight copolymer with a wide range of cationic strength. The flocculation effect was evaluated using sludge from wastewater of sugar manufacture. It was found that the radiation‐polymerized copolymer DMAEM·MC–AAm has an excellent flocculation effect.
Effect of uniaxial stretching on the tensile impact test for poly(ethylene terephthalate)
Authors: Yokouchi Mitsuru , Hiromoto Yasuyuki , Kobayashi Yasuji
Published: April 2003

In order to correlate impact strength with the structure of polymeric materials, a tensile impact test was carried out using a uniaxially stretched poly(ethylene terephthalate) (PET) sheet. The structural factors were the draw ratio (λ) and the cut‐out angle (θ) under the conditions of constant impacting speed (10.5 m/sec = 1.8 × 104%/sec) and temperature (20° ± 1°C). The occurrence of structural anisotropy by stretching of isotropic amorphous quench‐rolled PET was classified into three drawing stages: λ = −1.5 or 2.0, −3.5, and over 3.5. This is related to a deformation mechanism of masses with dimensions a few tenths of a μm and their boundaries. The boundaries are not clear until adiabatic deformation (mechanical impact) is applied. The area supporting the mechanical strength was limited to just a small section. Its character was affected by macroscopic deformation only in the direction parallel or near to the stretching direction, since the mechanical properties were not changed for the range of the cut‐out angle θ = 45–90°.
Polyester–polycarbonate blends. V. Linear aliphatic polyesters
Authors: Cruz C. A. , Paul D. R. , Barlow J. W.
Published: April 2003

Polycarbonate blends with the linear aliphatic polyesters poly(ethylene succinate) (PES), poly(ethylene adipate) (PEA), poly(1,4‐butylene adipate) (PBA), and poly(hexamethylene sebacate) (PHS) were prepared by solution casting. Blends containing PES, PEA, and PBA exhibited a single Tg by DSC and thus form a single, miscible amorphous phase with polycarbonate. However, blends containing PHS exhibited only partial miscibility. Crystallinity of the polyesters was reduced by mixing with polycarbonate; however, plasticization by the polyesters induced crystallization of the polycarbonate. Miscibility in these systems is the result of an exothermic heat of mixing stemming from an interaction of the carbonyl dipole of the ester group with the aromatic carbonate. The effect of polyester structure on miscibility with polycarbonate is interpreted by and correlated with heats of mixing obtained by direct calorimetry of low molecular weight liquid analogs of the polymers.
Mechanism of solvent crazing in unmodified and rubber‐modified polystyrenes
Authors: Iisaka K. , Shibayama K.
Published: April 2003

The dependence of critical strain on time was determined at −20° and 20°C with a Bergen elliptical strain device for unmodified and rubber‐modified polystyrenes immersed in n‐alcohols. Critical strain ϵc decreased with time and attained a lower limiting value ϵcl at long times. The value of ϵcl decreased with increasing chain length of the n‐alcohol and with increasing temperature, while it increased with increasing rubber content. In order to elucidate the mechanism of solvent crazing at longer times, the degree of equilibrium swelling Sveq and the diffusion coefficient D were also determined by sorption experiment. The lower limiting value of critical stress σcl was correlated to the value of Sveq, irrespective of the rubber content. The At, the time necessary to attain ϵcl, was regarded as the time needed for the thin layer of polymer surface to absorb the liquid to equilibrium for craze formation. The thickness of such a layer was estimated to be about 0.1 μm by using the experimental data of At and D. The predominant mechanism of solvent crazing at longer times appears to be a flow process of absorbed polymer at the craze tip.
Anion exchange resins prepared from polystyrene crosslinked via a Friedel–Crafts reaction
Authors: Belfer Sofia , Glozman Raisa
Published: April 2003

The preparation of anion exchange resins from polystyrene crosslinked via a Friedel–Crafts reaction is investigated. Chloromethylation of a highly swollen styrene–hexahydrotriacrylolyl‐s‐triazine copolymer with a mixture of chlorosulfonic acid and methylal is accompanied by the crosslinking of the initially flexible copolymer. The crosslinking efficiency is dependent on the conditions (temperature, nature of solvent) of chloromethylation and can be explained by cationic postpolymerization of polystyrene or poly(benzylchloride), which takes place concurrently with the chloromethylation.