bluuebunny/crossref_metadata_2025_split huggingface dataset:
A study of curative interactions in cis‐1,4‐polyisoprene. X. The cis‐1,4‐polyisoprene/sulfur/zinc dimethyldithiocarbamate and cis‐1,4‐polyisoprene/sulfur/zinc dimethyldithiocarbamate/ZnO systems
Authors: Kruger F. W. H. , McGill W. J. 
Published: April 2003

AbstractAspects of the mechanism of zinc dimethyldithiocarbamate (ZDMC)‐accelerated sulfur vulcanization were discussed. The trends in the efficiency parameter E, confirmed that crosslinking is preceded by the formation of pendent groups RSxSX [R = polyisoprenyl, X = Me2NC(S)] in ZDMC‐based systems. The index x in RSxX was calculated as 5.82 in the cis‐1,4‐polyisoprene (IR)/sulfur/ZDMC/ZnO compound at the initial stages of curing, compared to 3.23 in the absence of ZnO. The high value of x supports the postulation that elemental sulfur and ZDMC react at the early stages of vulcanization, to form the active sulphurating agent XSxSZnSSX. Crosslinks form by either a disproportionation reaction between two α‐methylic or α‐methylenic pendent groups RSxX, or a reaction between a pendent group RSxX and the rubber chain—these routes are the same as that suggested for the IR/tetramethylthiuram disulfide (TMTD)/ZnO compound. The beneficial role of ZnO and zinc stearate is shown, as in the case of ZnO in the IR/TMTD/ZnO system, to be related to their ability to trap dimethyldithiocarbamic acid, which formed in the generation of pendent groups and crosslinks. ZnS is inactive in this regard. The formation of ZnS is characteristic of natural rubber/sulfur/ZDMC/ZnO systems, as opposed to IR/TMTD/ZnO mixtures where little ZnS forms.
A study of the transport properties of acetylene through a highly oriented polyethylene fiber
Authors: Jones R. A. , Orchard G. A. J. , Ward I. M. 
Published: April 2003

AbstractThe transport properties of acetylene in a high modulus polyethylene fiber have been studied in detail over the temperature range of 25 to 65°C. Diffusion coefficients for the fiber are about four orders of magnitude lower than values cited for isotropic high density polyethylene. In keeping with this, a much higher apparent activation energy of diffusion (ca. 80.64 ± 0.53 kJ mol−1) was found. The solubility of acetylene in the fiber (ca. 0.158 cm3 C2H2 STP/cm3 PE @ 76 cm Hg), is lower, but of the same order of magnitude as that expected for isotropic polyethylene. The apparent heat of solution was determined, within experimental limits, to be zero. It is concluded that the acetylene is neither chemically nor physically absorbed onto the fiber, but freely diffuses, according to Fick's law, through the amorphous regions of the polymer.
Preparation and electrical properties of metal sulfides–amidoximated PAN composite film
Authors: Im Sung Soon , Lee Joon Sung , Kang Eun Young 
Published: April 2003

AbstractTo improve the electrical conductivity of polyacrylonitrile (PAN) film, metallic sulfides and PAN composite film were prepared by the chelating method. Dense PAN film and porous PAN film were prepared by dry process and wet process, respectively. These PAN films were treated to NH2OH solution to introduce the amidoxime group coordinated with metallic ion. Cu+2 and Cd+2 ions were adsorbed to amidoximated PAN films, the sulfur ion was treated with metal‐adsorbed PAN films, and thus CuS—and CdS–PAN composite films were prepared. The adsorptive capacity of amidoximated PAN film for the Cu+2 ion was independent of the morphology of the PAN film, but the adsorptive capacity of the Cd+2 ion on amidoximated PAN film was dependent on porosity of the polymer. Adsorptive capacity of amidoximated porous PAN film for Cd+2 was improved about four times than that of amidoximated dense PAN film. The electrical conductivities of CuS–dense and porous PAN composite film were both 10−1 S/cm in optimum condition, but because of the difference in adsorptive capacity, the electrical conductivities of CdS–dense and CdS–porous PAN composite films were 10−9 S/cm and 10−4 S/cm, respectively. Additionally, because CdS was known as a photoconductive material, the photoconductive properties of CdS–porous PAN composite film were investigated.
Recovery of uranium from seawater. X. Pore structure and uranium adsorption of macroreticular chelating resin containing amidoxime groups
Authors: Egawa Hiroaki , Nonaka Takamasa , Abe Syouichirou , Nakayama Morio 
Published: April 2003

AbstractEight types of amidoxime–type resin (RNH) were derived from macroreticular acrylonitrile—divinylbenzene copolymer beads, which were synthesized by varying the amount of polymerization initiator. Although these RNH are similar in chemical properties and physical pore structure, they exhibited different adsorption abilities for uranium. The porous structure of RNH in swollen state was analyzed by gel permeation chromatography in aqueous medium. The calibration curves yielded useful information on the pore structure of RNH in the swollen state and it was recognized that the pore structure in the swollen state is important for the improvement of the adsorption rate.
Macromolecular entanglement. III. Textural development of acrylic fibers
Authors: Qian B. J. , Qin J. , Wu Z. Q. , Wu C. X. , Hu P. P. , Zhao J. X. 
Published: April 2003

AbstractThe texture of a polymer (on fiber) is effectively developed by heat and stress. In this article, the chief material studied is acrylics, usually polyacrylonitile copolymer (PAC fiber) produced by Jingshan Jinglun Fiber Production Plant. In industry, the Jinglun acrylic fiber is heat treated, using saturated steam, at a temperature of 120–130°C to enhance its loop strength, reduce shrinkage, and stabilize crimp. At 140°C, the fiber becomes tacky and its good textile properties seem to deteriorate. At 150–160°C, the texture of the fiber seems to be deeply modified. Tested by differential scanning calorimetry (DSC) with the fiber immersed in a swelling agent (usually termed swelling DSC, abbreviated as SDSC), in addition to the entanglement peaks situated on the latter part of the thermogram of the Jinglun fiber, a new endothermic peak before the crystalline peak (actually, paracrystalline in the case of acrylic fiber) was discovered. The elastic recovery properties of the treated fiber under partially swelling conditions were improved. This seems to indicate that this preparacrystalline peak might also be concerned with entanglements.
Universal calibration for thermal field‐flow fractionation
Authors: Yushu Gao , Xiurong Chen 
Published: April 2003

AbstractExperiments have shown that the thermal diffusion coefficient of a polymer is independent of the sample's molecular weight. According to the relationship between the ordinary diffusion coefficient and polymer molecular weight, a universal calibration method for thermal field‐flow fractionation (FFF) has been created. This method has been examined experimentally by three polymers of different chemical composition with different molecular weight in three organic solvents. It is shown that this method is useful both in terms of calibrating a thermal FFF system with some readily available polymer standard, for use with unknown samples of known thermal diffusivity, and in terms of determining the thermal diffusion coefficient of the unknown sample under conditions where its molecular weight can be measured by other methods.
Preparation of polymer‐supported schiff base iron (III) complexes and their catalytic activity for decomposition of hydrogen peroxide
Authors: Wang Xin , Gu Weihong , Lu Lude , Chen Zhijin , Stevens John G. 
Published: April 2003

AbstractPolymeric substrates containing salicylidenimine ligands as discrete units can be obtained by reacting chloromethylated divinylbenzene styrene copolymer with amines, followed by condensation with salicylaldehyde. Polymer‐supported Schiff base iron (III) complexes have been prepared and their IR spectra and Mössbauer spectra measured. Catalytic activity of supported complexes have been tested using decomposition of hydrogen peroxide as a model reaction.
Rheology of neck formation in the cold drawing of polymeric fibers
Authors: Coleman Bernard D. , Newman Daniel C. 
Published: April 2003

AbstractAn asymptotic formula has been obtained for the axial tension in nonlinear viscoelastic fibers undergoing inhomogeneous stretch. The formula, which is valid to within an error of the fourth order in diameter, expresses the tension per unit cross‐sectional area in terms of the history of the local axial stretch and its first two derivatives with respect to distance along the fiber axis. The theory obtained by treating the formula as exact is consistent with thermodynamical principles, and permits computation of the stretch field resulting from a specified tensile loading history. Numerical results for creep under static load show that for an appropriate class of materials with slowly fading memory there is a range of applied loads for which an initially homogeneous deformation evolves into a well‐defined neck whose edges, after a period of relatively quiescent incubation, advance rapidly along the fiber and in so doing transform moderately stretched material into highly stretched, i.e., drawn material. The calculated fiber profiles and the predicted dynamics of neck formation are in accord with familiar observations of neck formation in polymeric materials susceptible to cold drawing.
Natural and artificial weathering of low‐density polyethylene (LDPE): Calorimetric analysis
Authors: Sebaa M. , Servens C. , Pouyet J. 
Published: April 2003

AbstractStudies of the thermal and photodegradation of two commercial polymers, stabilized and unstabilized low‐density polyethylene (LDPE), show the effects of weathering in differential scanning calorimetry (DSC) curves. The shape and the size of the melting peak vary significantly in thermal aging and in accelerated photoirradiation, but no change was observed in natural weathering implying that the crystallinity remains steady in outdoor exposures. The melting temperatures remain steady for all exposure tests. The fall of mechanical properties and the evolution of chemical structure, followed by IR spectroscopy especially near the carbonyl regions, was also performed. The resistance to UV light irradiation as probed by deformation at break was superior in stabilized LDPE compared to unstabilized LDPE. Simple correlations were not observed between the fall of mechanical properties, the rate of oxidation, and the morphology.
Reactive extrusion vs. batch preparation of starch–g–polyacrylonitrile
Authors: Yoon K. J. , Carr M. E. , Bagley E. B. 
Published: April 2003

AbstractAcrylonitrile (AN) was graft polymerized onto unmodified cornstarch by a continuous reactive extrusion process and, for comparison, by a typical batch reaction process. The effect of AN/starch weight ratios, level of ceric ammonium nitrate (CAN) initiator, starch in water concentration, reaction temperature, reaction time, and extruder screw speed in the reactive extrusion process was studied. Add‐on, reaction efficiency, grafting frequency, weight average molecular weight (MW) and MW distribution of polyacrylonitrile (PAN), and water absorbency of the saponified copolymers were determined. Processing times in the twin‐screw extruder (ZSK) were 2–3 min, and total reaction time was about 7 min before reaction of the extruded material was terminated, compared to a reaction time of 2 h used in the typical batch procedure. The continuous reactive extrusion process was found to be a rapid and efficient means of preparing St‐g‐PAN with high add‐on (% PAN of the grafted product). For example, 42% add‐on was achieved within the 7‐min reaction period using an AN/starch weight ratio of 1.0 (3.5% CAN, starch weight basis), as compared to 38–49% for the 2‐h batch process (0.75–1.5 AN/starch ratio). Percentages of homopolymer of the copolymers were low for both extrusion and batch processes. Grafting frequencies were substantially higher while MWs were significantly lower for grafts from the extrusion process. Water absorbency of the saponified St–g–PAN products was somewhat greater for the products prepared by the batch process.
Studies on characteristics and mechanisms of X–MoO3 synergism in fire‐retarded epoxy resin
Authors: Xiaoming Xu , Shiyuan Cheng , Jianzong Li 
Published: April 2003

AbstractMolybdenum trioxide was incorporated into epoxy resin, containing halogen additive, and the performance of the system was studied. The results from LOI measurements show that X–MoO3 synergism in fire‐retarded epoxy resin depends on the levels both of halogen and MoO3, and that when Mo/X ratio is 1/3, the maximum fire retardancy is not found in the synergistic combination. The thermal analysis was carried out by thermogravimetry (TG), differential scanning calorimetry (DSC), X‐ray diffraction, and laser Raman spectroscopy. The results indicate that MoO3 acts as a synergist in condensed phase. The mode of X–MoO3 synergism in fire‐retarded epoxy resin in proposed.
Theory‐based improvements of continuous polymer fractionation demonstrated for poly(carbonate)
Authors: Weinmann K. , Wolf B. A. , Rätzsch M. T. , Tschersich L. 
Published: April 2003

AbstractFor the first time, a quantitative theoretical analysis (liquid/liquid phase equilibria treated by means of the continuous thermodynamics) of the operating characteristics of continuous polymer fractionation (CPF) was performed. The results of these calculations were compared with data published for CPF of polyethylene. It turned out that the efficiency of the conventional CPF corresponds to approximately two theoretical plates only. For this reason, several improvements, suggested by theoretical considerations, were realized experimentally, for which purpose the system dichloromethane/diethylene glycol/bisphenol‐A polycarbonate was chosen. The pulsating sieve‐bottom column was replaced by a nonpulsating column filled with glass beads. In this manner, the number of theoretical plates could be raised considerably. A further improvement of the fractionation efficiency results from the reflux of part of the polymer contained in the sol phase. In praxi, this situation was realized by putting a condensor on top of the column and introducing the feed somewhere near its upper third. After predictive calculations and orienting experiments, 125 g of a polycarbonate with Mw = 29 kg/mol and a nonuniformity U = 1.3 were fractionated in four consecutive CPF runs (where the gels were directly used as feed for the next step) into five fractions of approximately equal weight. Except for the lowest‐molecular‐weight fraction, one obtains nonuniformities on the order of 0.1.
Corrosion protection of steel and bond durability at polyphenylene sulfide‐to‐anhydrous zinc phosphate interfaces
Authors: Sugama T. , Carciello N. R. 
Published: April 2003

AbstractTo enhance the performance of high‐temperature polyphenylene sulfide (PPS) coating in protecting steels from corrosion, the cold‐rolled steel surfaces were prepared with anhydrous zinc phosphate (Zn · Ph) conversion coatings containing poly(acid) anhydride as an interfacial tailoring material. The factors contributing to the formation of a good bond at the PPS/Zn · Ph joints were as follows: (1) the chemical reaction of PPS with Fe2O3 in the Zn · Ph layers, (2) PPS‐to‐poly(acid) anhydride interaction, and (3) the mechanical interlocking between PPS and the rough Zn · Ph crystal surfaces. Although such interfacial bond structures provide a superior durability of PPS/Zn · Ph joints against a hot H2SO4 solution, the cathodic reaction, H2O + ½O2 + 2e− = 2OH−, occurring at any defect in the PPS/Zn · Ph joint system when NaCl is present will lead to the delamination of the PPS film from the phosphated steel. This cathodic delamination was due mainly to alkali‐induced dissolution of Zn · Ph layers. However, the rate of delamination for the PPS/Zn · Ph systems was considerably lower compared with that for the PPS/steel system in the absence of Zn · Ph.
Adhesive monomers to dental ceramics. I. Evaluation of N‐substituted 3‐amino‐2‐hydroxypropyl methacrylates as adhesives for calcium metaphosphate crystalline glass‐ceramic
Authors: Kitoh Shinya , Suzuki Kunitomo , Kiyohara Takao , Kurita Keisuke 
Published: April 2003

AbstractN‐Substituted 3‐amino‐2‐hydroxypropyl methacrylates have been evaluated as adhesives for calcium metaphosphate crystalline glass‐ceramic, a potential esthetic dental restoration material. Although the adhesion to the ceramic was found to be much more difficult and dependent on the kinds of substituents than that of tooth enamel, monomers having a carboxyl group showed specifically high adhesive tensile strength. The strength tended to decrease as the hydrophobicity and molecular bulkiness increased. Surface treatment of the ceramic, especially with sodium hydroxide, proved effective in terms of both strength and durability for the carboxyl‐containing monomers. Scanning electron microscopy analysis confirmed the importance of surface irregularity due to the alkaline treatment.
The effects of functional azo initiator on PMMA and polyurethane IPN systems. II. The influence of the interface and the matrix structure on the mechanical properties
Authors: Roha M. , Dong F. 
Published: April 2003

AbstractThe mechanical properties of materials prepared by a new method for modifying the structure of polyurethane/poly(methyl methacrylate) (PU/PMMA) interpenetrating polymer networks (IPNs) by using a reactive azo initiator were investigated by means of tensile test, tear test, and dynamic mechanical thermal analysis (DMTA) measurement. The structures of these IPNs were similar to the particulate filled elastomers. It was found that the reactive initiator, which could form blocks of PMMA within the PU matrix (rubber), changed both the filler‐matrix interface and the matrix structure. The mechanical properties of these IPNs were dominated by the matrix structure and the interface.
Following of the relaxations in a polymer's behavior part II: Characterization by quasistatic and dynamic forced bending
Authors: Guerrin G. M. , Genevaux J. M. 
Published: April 2003

AbstractThe aim of this work is to quantify the internal loss in polymers, for frequencies near 1 Hz, and including the domain (100 and 3000 Hz). The quasistatic experiment used the double‐pendulum method; the other experiments were forced vibrations in bending. Two materials were tested between 20 and 60°C, PMMA and wood. Owing to the anisotropy of the wood, the different mechanisms that induce internal loss are located in the matrix or in the reinforcement (fiber) of this composite. The results were plotted on the correlation diagrams, presented in the first part of this study.
Adsorption mechanism of heavy‐metal ion by microspherical tannin resin
Authors: Yamaguchi H. , Higasida R. , Higuchi M. , Sakata I. 
Published: April 2003

AbstractThe spherical tannin resin (STR) resulting from the reaction between Mimosa (Acacia Mollissima) tannin (condensed‐type tannin) and formaldehyde was very porous. The specific surface area of the STR made from 37.5% of tannin was 139.2 m2/g (1 g of the resin in this is wet resin corresponding to 1 g of dried resin). Properties such as specific surface area and average pore radius could be controlled by adjusting the tannin concentration. The apparent activation energy of Cu2+ion adsorption by STR was 3 kcal/mol, and that of Cr6+ion was 2 kcal/mol. Since the energy was small, we concluded that the adsorption of metal ions was not influenced significantly by the adsorption temperature. The heat of adsorption for Cu2+ions was only 1.6 kcal/mol, which suggests that the adsorption was a physical phenomenon. It was thought that the diffusion of heavy‐metal ions into the porous resin was the rate‐determining step of the adsorption since the elution profile of the column method was analogous to the profile of active carbon, which adsorbs physically, the heavy metal ions gradually leaking through the column. The surface and cross section of the STR were observed before and after Cu2+ion adsorption with the scanning electron microscope. The pores of the spherical resin were clogged with adsorbed copper, suggesting that the Cu2+ions were adsorbed during the formation of a multimolecular layer. The adsorption may therefore have been due to physical attractive forces. The rate of adsorption and adsorption isotherms of Cu2+ions from copper salts having various anions was found to vary depending on the type of anion. These phenomena were not thought to be due to the properties of the spherical resin but to differences in the hydration state of copper ions.
Response of filled polyethylene membranes to the changes in the environmental conditions
Authors: Islam M. A. , Nikolov N. D. 
Published: April 2003

AbstractThe environmentally sensitive properties of polyethylene membranes filled with SiO2 have been studied. The porous characteristics of the membranes is investigated with the aqueous solutions of pH 1–8 and aqueous electrolyte solutions with concentrations of 10−5–10−1 mol/L. The experimental results are explained by the concept of coagulation‐swelling behavior of the filler under different environmental conditions. The relaxation of membrane resistance with a change in pH is also studied.
Study of curative interactions in cis‐1,4‐polyisoprene. XII. The cis‐1,4‐polyisoprene–sulfur–tetramethylthiuram disulphide–ZnO–stearic acid vulcanization system
Authors: Kruger F. W. H. , McGill W. J. 
Published: April 2003

AbstractSeveral aspects on the mechanism of vulcanization in the synthetic cis‐1,4‐polyisoprene (IR)‐sulfur‐tetramethylthiuram disulphide (TMTD)–ZnO system were harmonized. The differential scanning calorimetry (DSC) thermograms showed that the vulcanization processes became better resolved on increasing the curative loading in the compound. Two major crosslinking reactions occurred consecutively in the IR (100)–sulfur (9.46)–TMTD (8.86)–ZnO (3.00) mixture, viz the IR–sulfur–TMTD–ZnO and IR–sulfur–zinc dimethyldithiocarbamate (ZDMC) (or IR–sulfur–ZDMC–ZnO) reactions. In the first process poly‐and disulfidic pendent groups RSxSX (R = polyisoprenyl, X = Me2NC (S), x ≥ 1) formed via the IR–XSSxSX reaction, and in the second via the IR–XSSxZnSSX reaction. Thermogravimetric analysis (TGA) and high‐pressure liquid chromatography (HPLC) data showed that dimethyldithiocarbamic acid liberated during the IR–sulfur–TMTD–ZnO reaction was trapped by ZnO to yield ZDMC. Hence ZDMC was a product, and not precursor, of this crosslinking process. A comparison of reactions in IR–sulfur–TMTD–ZnO and poly(ethylene‐co‐propylene)–sulfur–TMTD–ZnO mixtures showed that the participation of IR molecules was essential for ZDMC formation. The ZDMC concentration remained constant at ∼ 38.4 mol % during the later stages of cure, showing that it did not participate in the desulfuration reactions of polysulfidic links. In the presence of stearic acid the stearic acid–ZnO reaction occurred at 87°C as was manifested by an intense crystallization peak of zinc stearate. The vulcanization processes were the same both in the presence and absence of stearic acid.