bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement of shear‐dependent intrinsic viscosities of carboxymethyl cellulose and xanthan gum suspensions
Authors: Young San Land , Shoemaker Charles F. 
Published: April 2003

AbstractA rotational rheometer with cone and plate fixtures was used to measure the intrinsic viscosities of aqueous suspensions of xanthan gum and carboxymethyl cellulose (CMC). The reduced viscosities or hydrodynamic volumes of CMC suspensions increased with dilution. However, the reduced viscosities of xanthan gum suspensions decreased with dilution within the concentration range of 0.1–0.06% and increased with dilution within the concentration range of 0.04–0.01%. When the gums were suspended and diluted with 0.06 M sodium acetate, the reduced viscosities of all the xanthan gum and CMC suspensions decreased upon dilution. The intrinsic viscosities of xanthan gum and CMC suspensions decreased with increasing the shear rate, showing a dependence of hydrodynamic volume on shear rate.
Effect of physical annealing on the dynamic mechanical properties of a high‐Tg amine‐cured epoxy system
Authors: Wisanrakkit G. , Gillham J. K. 
Published: April 2003

AbstractPhysical annealing of a fully cured amine/epoxy system has been investigated using the freely oscillating TBA torsion pendulum technique. The material densifies spontaneously during annealing in an attempt to reach equilibrium, thereby changing material behavior. The dynamic mechanical behavior of a film specimen (Tg = 174°C, 0.3 Hz) and of a glass braid composite specimen (Tg = 182°C, 0.9 Hz) was monitored during isothermal annealing at sub‐Tg temperatures (ranging to 230°C below Tg); after annealing, the behavior was measured vs. temperature and compared with that of the unannealed state. Isothermally, the storage modulus (G′) of the film specimen and the relative rigidity (1/P2) of the composite specimen increased almost linearly with log time, whereas the logarithmic decrement (Δ) decreased with time. The isothermal rates of annealing were determined from the rates of changes in G′ and in 1/P2 for the film and composite specimens, respectively. In a wide temperature range between Tg and the secondary transition temperature, Tsec (≈ −30°C, 2.3 Hz by TBA), the isothermal rates of annealing at the same annealing time appeared to be the same. Thermomechanical spectra of the isothermally annealed material revealed a maximum deviation in thermomechanical behavior from the unannealed material in the vicinity of the annealing temperature. The effects of physical aging were the same for the film and composite specimens. Effects of sequential annealing at two isothermal temperatures on the thermomechanical behavior were also investigated; when the second temperature was higher than the first, the effect of only the high‐temperature annealing was evident, whereas the effect of annealing at both temperatures was revealed when the second temperature was lower than the first. Results suggest that physical annealing at different temperatures involves different length scales of chain segment relaxation and that the effects of isothermal aging can be eliminated by heating to below Tg.
A DSC study of curative interactions. I. The interaction of ZnO, sulfur, and stearic acid
Authors: Kruger F. W. H. , McGill W. J. 
Published: April 2003

AbstractThe interaction between combinations of sulfur, stearic acid, and ZnO were studied by differential scanning calorimetry in the absence of rubber. The only reaction observed was between ZnO and stearic acid. A small amount of zinc stearate formed as soon as the stearic acid melted, but the solid product blocked further reaction, which was only completed at 154°C. Water played a major role in the reaction, and in the presence of water, the reaction went to completion at lower temperatures. Sulfur, too, affected the temperature of the ZnO/stearic acid reaction. The preparation of zinc stearate by a number of routes was investigated.
Refractive index of solutions containing poly(vinyl acetate) and poly(methyl methacrylate)
Authors: Bahr D. , Pinto J. C. 
Published: April 2003

AbstractRefractive index measurements can be used successfully for on‐line evaluation of extent of reaction in solution polymerization reactors. For this reason, the refractive index of solutions containing tert‐butanol (TBOH), methyl methacrylate (MMA), vinyl acetate (VA), poly(methyl methacrylate) (PMMA), and poly(vinyl acetate) (PVA) were measured and a mathematical correlation was developed to fit the experimental data. The correlation can be extended to fit published data obtained with different solvents.
Hydrolytic stabilities of some polyurethane hydrogels
Authors: Lai Yu‐Chin 
Published: April 2003

AbstractThe hydrolytic stability of some polyurethane hydrogels derived from UV‐curable urethane prepolymers and hydrophilic monomers was addressed. It was found that polyurethane hydrogels derived from prepolymers with hydrophilic polypropylene glycol soft segments were not stable when the films were cast from nonpolar solvent, whereas they are stable if the films were cast from neat monomer mix. The causes for this instability were analyzed. Spectroscopic and gel permeation chromatographic studies of the water extractables suggested that improper curing of hydrophilic monomers with the urethane prepolymers in nonpolar solvent was mainly responsible for the instability phenomenon.
Effect of tensile deformation on the electrical conductivity of SRF black‐loaded SBR blend
Authors: Hassan H. H. , Khairy S. A. , El‐Guiziri S. B. , Abdel‐Moneim H. M. 
Published: April 2003

AbstractStyrene butadiene rubber (SBR‐1502) was mixed with 100 phr superreinforcing furnace (SRF) black. The obtained rubber vulcanizate was subjected to electrical conductivity measurements at different values of tensile deformation. The log V vs. log I graphs showed two distinct linear stages, the slope of which is nearly independent of the tensile deformation in the first stage and decreases with tensile deformation in the second stage. On the other hand, the tensile deformation was found to have an appreciable effect on the electrical conductivity. It decreases sharply as the sample is suddenly strained and then increases exponentially with time. An empirical formula describing this behavior is suggested.
Blends of thermotropic polyester with poly(phenylene oxide)
Authors: Limtasiri T. , Isayev A. I. 
Published: April 2003

AbstractA thermotropic liquid crystalline polymer (LCP) based on wholly aromatic copolyesters based on hydroxynaphthoic and hydroxybenzoic acid was melt‐blended with a thermoplastic poly(phenylene oxide) by corotating twin screw extruder. Rheological properties, temperature transitions, dynamic and mechanical properties, and electron microscopy study have been performed. Rheological study indicated significant viscosity reductions with increasing LCP content leading to ease of processing. From the differential scanning calorimeter (DSC) and dynamic mechanical thermal analyzer results, these blends showed incompatibility for the whole range of concentrations. Mechanical properties were found to be slightly improved at low LCP and dramatically improved at above 50% LCP contents. In addition, impact strength was significantly increased up to two times after adding 10% LCP into the matrix. The morphology of blends was affected by composition. Droplets and stubby fibrils structures caused lower tensile strength, whereas fibrillar structure improved this property.
On the synthesis and properties of some saturated and unsaturated esters of 2‐cyano‐2, 4‐pentadienoic acid
Authors: Denchev Z. Z. , Kabaivanov V. S. 
Published: April 2003

AbstractThe preparation and properties of some new saturated and unsaturated esters of 2‐cyano‐2,4‐pentadienoic acid (CPDA) are described. A comparison is also made with the known CPDA monomers synthesized under identical conditions. It was found that the monomer yields are dependent on the structure of the corresponding CPDA esters. This fact was explained with solvatation effects, occurring during the isolation procedures. The base‐catalyzed anionic bulk polymerization of CPDA esters was studied by means of spectral methods. The data indicated that during the homopolymerization 1,4‐addition of monomer molecules takes place to give a steric copolymer consisting of 1,4‐cis and 1,4‐trans structural units. The ability of poly‐CPDA esters was also followed to form crosslinks at room and higher temperatures.
Effects of temperature, repeated exposure, and aging on polybutylene permeation by organic chemicals
Authors: Park J. K. , Bontoux L. 
Published: April 2003

AbstractThe permeation parameters, partition coefficient and diffusion coefficient, were obtained for polybutylene (PB) with toluene using a gravimetric method. A PB sample was repeatedly exposed and desorbed, and the partition coefficient and diffusion coefficient were measured. Permeation parameters were also measured at different temperatures. The results were compared with those obtained from a 12‐year‐old PB pipe sample, which had experienced structural failure. Tests at an elevated temperature of 45°C failed to simulate the effect of polymer aging, whereas repeated sorption/desorption tests produced permeation parameters compatible with those of a 12‐year‐old PB pipe in service.
Diffusion coefficients of direct dyes in chitosan
Authors: Carlough Mark , Hudson Sam , Smith Brent , Spadgenske Dawn 
Published: April 2003

AbstractDiffusion coefficients for direct dyes (C. I. Direct Red 81, Green 26, Blue 75, and Black 22) in Chitosan films are determined to be 4.48 × 10−11 to 4.54 × 10−10 cm2/at 60°C and pH 9. A method for producing chitosan films is described.
Vinylic graft copolymers of cellulose. I. Effects of monomer concentrations and crystallinity index of cellulosic substrate on grafting vinyl acetate onto cotton
Authors: Flaqué C. , Montserrat S. 
Published: April 2003

AbstractGraft copolymerization of vinyl acetate (VA) and methyl acrylate (MA) on cotton cellulose was initiated by the Ce (IV) ion, and ungrafted vinylic polymer was separated from the graft copolymer by acetone extraction. The influence of the ratio aqueous initiator solution volume/monomeric volume (Vaq/Vmon), vinyl acetate volume/methyl acrylate volume (VVA/VMA), and the cellulose crystallinity index (CI) on the grafting reaction were studied. To modify the crystallinity of cellulose, native cotton was treated with NaOH in the concentrations 10, 15, and 20% (mercerized). The viscosimetric average molecular weight (Mv), the polymerization degree (PD), and the crystallinity index proposed by Nelson and O'Connor (CI) were determined for native and NaOH‐treated cotton. The polymeric side chains grafted were separated from the cellulose backbone by acid hydrolysis in 72% H2SO4. The viscosimetric average molecular weight (Mv) was determined, and the number of vinylic chains per cellulosic chain (graft frequency, GF) were calculated. The grafting percentage, %G, was higher for most amorphous cellulose and for a higher methyl acrylate percentage (%MA) in monomeric reaction mixtures (VA‐MA). The Vaq/Vmon ratio that yields the highest %G was 70/30. The increase of the %G with the %MA in the VA–MA monomeric mixture seems to be due to both an increase in the length of vinylic grafted chains (as shown by its Mv) and the number of grafted chains (GF). The increase in the %G when the crystallinity index (CI) of the cellulosic substrate decreases seems to be due to an increase in the length of the vinylic grafted chains, but not to an increase in the number of grafted chains, since the Mv increases and GF decreases when the CI of cellulose decreases.
Emulsion copolymerization of vinylidene chloride and butyl methacrylate, 83:17 in mol %
Authors: Lee Ki‐Chang , El‐Aasser M. S. , Vanderhoff John W. 
Published: April 2003

AbstractSeven 35% solids, (83 : 17 in mol %), vinylidene chloride (VDC)–butyl methacrylate (BMA) copolymer latexes were prepared at 25°C using redox catalyst by batch and seeded semicontinuous emulsion copolymerization processes: one batch (G), one seeded batch (F), and five seeded semicontinuous polymerizations of five different monomer feed rates ranging from 0.27 (A) to 1.10 (E) wt %/min. All of the emulsion polymerizations gave stable latexes of almost 100% conversion with negligible coagulum and narrow particle size distributions. The kinetic studies of seeded semicontinuous polymerization A–E showed that the rates of polymerization (Rp) were controlled by the monomer addition rates (Ra), and polymerizations A–D (0.27–0.79 wt %/min) were under monomer‐starved conditions; polymerization E (1.10 wt %/min) was in near‐flooded condition. Significant differences were found in the physical and mechanical properties of the latex films, depending on the mode of monomer addition. Infrared spectroscopy, 13C solid‐state NMR spectroscopy, X‐ray diffraction, the Tg and Tm values by DSC, dynamic mechanical spectroscopy, and tensile strength measurement of the latex films post‐heat‐treated for 30 min at 70°C or aged for several months at room temperature demonstrated that batch polymerizations F and G gave copolymers of heterogeneous composition and a crystalline character. In contrast, semicontinuous polymerizations A–E gave copolymers of more uniform composition and an amorphous character.
Investigation of structural and mechanical properties of copper‐chloride‐doped nylon‐6 films. I. Structure
Authors: Kelkar D. S. , Bhat N. V. 
Published: April 2003

AbstractStructural changes in nylon‐6 film on doping with various concentrations of copper chloride (0.5, 1.25, 2.5, 5, and 12.5% w/w) have been investigated. Methods such as density measurement, analysis of infrared spectra, and wide‐angle X‐ray diffraction analysis have been employed to study these structural changes. It is found that doping up to 1.25% of copper chloride increases the crystallization of nylon‐6 in the α‐crystalline form. Further increase in the dopant concentration, however, gradually changes the crystal structure to hexagonal γ form with reduction in the total crystallization.
Preparation and characterization of polyelectrolyte copolymers containing methyl methacrylate, and 2‐hydroxyethyl methacrylate. II. Polymers based on dimethylaminoethyl methacrylate
Authors: Wen Shao , Yin Xiaonan , Stevenson William T. K. 
Published: April 2003

AbstractCo‐ and terpolymers containing dimethylaminoethyl methacrylate (DMAEMA), methyl methacrylate (MMA), and 2‐hydroxyethyl methacrylate (HEMA) were prepared by solution polymerization, and characterized by dilute solution viscometry and proton and carbon‐13 nuclear magnetic resonance spectroscopy. Polymers were prepared containing 75, 60, 40, 25, and 10 mol % DMAEMA but with differing levels of MMA and HEMA. Polymer solutions were titrated under nitrogen to obtain variations of pKb with alpha (the extent of protonation of the DMAEMA residue). From these experiments, we were able to show that, as expected, the cooperative nature of the ionization process decreased as the level of DMAEMA in the polymer was reduced from 75 mol % to 10 mol %. By comparing polymers containing similar amounts of DMAEMA monomer, we were also able to show that base strength increased with the polarity of the uncharged portion of the polymer, in other words, that polymers containing higher levels of HEMA were stronger bases than polymers containing higher levels of MMA. This effect was rationalized by assuming that higher contents of the more polar HEMA monomer facilitated the coil expansion that accompanied the process of ionization, thus increasing charge separations at corresponding values of alpha and increasing base strength.
Kinetics of sol‐to‐gel transition for poloxamer polyols
Authors: Wang P. , Johnston T. P. 
Published: April 2003

AbstractKinetics of gelation for aqueous solutions of poloxamers 407 and 288 were determined using pulse shearometry. The principle of this method for determining the shear modulus of a semisolid was based on generation of a torsional force that is transmitted through the poloxamer sample at discrete time intervals. Three distinct linear phases were observed for the log dynamic shear modulus (G′) vs. time profiles as poloxamer 407 and 288 solutions of varying concentrations were allowed to passively warm at room temperature to a temperature exceeding the sol‐to‐gel transition temperature, Tm. The beginning of the second exponential phase coincided with the onset of the gelation process as determined by visual observation. Although gelation appeared visually to be complete at the beginning of the third exponential phase of the log G′ vs. time profiles, this last exponential phase may indicate the rate of formation of the polymer network. A comparison of poloxamer 407 [30% (w/w); Tm = 10.9°C] and poloxamer 288 [37% (w/w); Tm = 11.1°C] would suggest that the concentration of poloxamer required to achieve approximately the same gelation temperature for poloxamers having a similar ratio of poly(oxypropylene):poly(oxyethylene) units decreases with increasing molecular weight of the poly(oxypropylene) hydrophobe contained in the copolymer. Results of these preliminary studies suggest that the gelation process was significantly (p < .05) more rapid for poloxamer 407 at a 30% (w/w) concentration compared to a 30% (w/w) solution of poloxamer 288 when the poloxamer solutions were allowed to passively warm at room temperature. In addition, it appears that the rate of gelation for the poloxamer solutions studied was dependent on the rate of heat transfer through the polymer solution.
Processing–crystallization kinetics–morphology relationships in injection molding of PP and GFRPP
Authors: Chu Wen‐Yen , Tai Horng‐Jer , Chen Leo‐Wang , Chu Line‐Hwa 
Published: April 2003

AbstractThe dynamic crystallization model proposed in our previous work was applied to the simulation of crystallization kinetics and morphology of PP and PP/glass fiber composite (GFRPP) in injection molding process. The cooling rate was very rapid in the processing, either in the core or in the skin region of thin disc part, so that the crystallization would take place at low temperatures and the size of spherulites was small. However, the ultimate crystallinity of PP could always be obtained since the crystallization rate of PP was extremely fast. Prediction of the crystallization morphology from the dynamic model agreed well with the experimental observation, which indicated that our proposed model could give a good estimation of processing–crystallization kinetics–morphology relationships for PP and GFRPP.
Electron‐beam irradiation‐induced grafting of acrylonitrile onto polyethylene
Authors: Mori K. , Koshiishi K. , Masuhara K. 
Published: April 2003

AbstractLow‐ and high‐density polyethylene (PE) films were grafted with acrylonitrile (AN) by electron beam prior to irradiation. The distribution of graft chains over the cross section of the sample film was analyzed in terms of the distribution of nitrogen atoms contained in the AN by means of an electron probe microanalyzer (EPMA), and graft sites were studied in relation to the effect of grafting temperature on the percent graft and the oxygen permeability of the sample films. It was found that diffusion of AN into the film was the rate‐limiting step in the grafting process, thus restricting the grafting to the surface of the film in the initial grafting stages. However, the grafting shifted to the center of film as the graft process proceeded, until a uniform distribution of graft chains was observed across the entire film thickness. High‐density polyethylene (HDPE) was found to display a higher percent graft than did low‐density polyethylene (LDPE), and percent graft tended to increase with increasing grafting temperature. On the other hand, film oxygen permeability decreased with increasing percent graft, but this decreasing trend decreased with increasing percent graft. These findings suggest that the grafting is initiated by radicals trapped in the amorphous phase near the crystalline regions and at the surface of crystallites and that graft chains grow toward the amorphous regions. As for the radicals contributing to graft polymerization, it appears that AN permeates deeper near the crystalline surface and that graft chains grow from these sites.
Effect of orientation on melting of isotactic polypropylene
Authors: Ibhadon A. O. 
Published: April 2003

AbstractThe effect of uniaxial orientation on the melting of a commercial grade of isotactic polypropylene has been investigated by thermal analytical techniques. Orientation progressively shifts the onset of and the observed melting point to higher temperatures and increases the peak heights of differential scanning calorimetric (DSC) endotherms. The increase in melting point with orientation is attributed to the increase in configurational entropy of the extended melt into which the polymer crystallites melt.
Polyurethane elastomers studied by the Mooney–Rivlin equation for rubbers
Authors: Spathis G. D. 
Published: April 2003

AbstractA series of poly(ester–urethane) block copolymers were prepared via a two‐step polymerization process. The prepolymer composition was kept constant in all the samples, while the NCO/OH ratio during extension was varied from 0.9 up to 1.2. By this way, chemical and physical cross‐links were constructed into the materials. Equilibrium stress–strain measurements have been carried out for the examination of the elastomeric behavior of the materials tested. Calculation of an extra entropy term resulting from the network deformation is based on a first‐principles derivation of the distribution function, taking into account a new type of network constraints. The process yields the Mooney–Rivlin equation and the constant C2 as a function of physical cross‐links.
Residual birefringence of amorphous polymers for optical‐disk substrates
Authors: Shindo Y. , Saito M. , Iwatsuka Y. , Hasegawa H. 
Published: April 2003

AbstractBased on the Mueller matrix approach, we have successfully designed and constructed a highly sensitive instrument for measuring optical birefringence (LB) by using a polarization modulation method and phase‐sensitive technique. Our instrument can measure the retardation of a sample up to 10−2 radian. Using this instrument, we have measured the residual birefringence of thermosetting resins, CR‐39 resin and epoxy resin, for opticaldisk substrates. CR‐39 resin results are summarized as follows: (1) Annealing is very effective in reducing LB of samples; (2) samples prepared from raw material 2 (monomer purity, 96%, oligomer, 4%) have smaller LB than those from raw material 1 (monomer purity, 99.9%); and (3) annealed samples prepared from 2 satisfy the requirement on LB to be used as optical‐disk substrates. For epoxy resin: (1) “Second curing” largely reduces LB of samples; (2) “slow cooling” is more effective in reducing LB of samples than “fast cooling;” (3) after the second curing, cutting does not induce any residual stress birefringence in samples; and (4) slow‐cooled samples have good optical properties to be used as optical disk substrates.
Solution process of suspension poly(vinyl chloride) in cyclohexanone by means of a viscometer
Authors: Szewczyk Pawel , Gruszka Marianna , Bortel Krzysztof 
Published: April 2003

AbstractTo study the structure of grains of suspension poly(vinyl chloride) (PVC), the authors applied a capillary viscometer for cyclic measurements of viscosity of the PVC–cyclohexanone solution during dissolution of the polymer. Final concentration of the solution was 0.5–1.0 g/100 cm3 and the measurements were made at temperatures of 313, 333, 353, and 373 K. It was found that at 353 K, a temperature close to the glass transition temperature of PVC, the curve describing changes of viscosity vs. the dissolution time has a pronounced maximum. It follows from a preliminary analysis of the obtained results that this maximum corresponds to the viscosity of a PVC solution in which average apparent mass is many times larger than true average molecular mass of the studied sample. It mans that into the solution enter single chains and some formations, called microdomains in the literature, that are composed of tens of macromolecules. The microdomains disintegrate later to single macromolecules.