bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of polyesterification of 1,3‐(dicarboxymethoxy) benzene with tetraethylene glycol
Authors: Shaaban A. F. , Moustafa H. Y. , Messiha N. N. 
Published: April 2003

AbstractThe polyesterification of 1,3‐(dicarboxymethoxy)benzene with tetraethylene glycol in both equimolar and nonequimolar ratios were studied over the range of 120–160°C in the absence and presence of p‐toluenesulphonic acid as catalyst. The experimental results for uncatalyzed reactions agreed quite well with the kinetic equation proposed by Flory. The kinetic equations for acid‐catalyzed reactions, however, are in agreement with the kinetic equation proposed by Lin and Hsieh. The kinetic equations were −d[COOH]/dt = k1[COOH]2[OH] and −d[COOH]/dt = k2[COOH]2 for uncatalyzed and acid‐catalyzed polyesterfications, respectively. The rate constants for uncatalyzed and acid‐catalyzed reactions were calculated by using the method of least squares for various values of initial molar ratio between [OH] and [COOH]. Also, the activation energies were calculated.
Rheological behavior of ultrahigh molecular weight polyethylene semidilute solutions. II. Effect of aluminium stearate
Authors: Chen Kequan , Zhang Anqiu , Lu Pin , Wu Zongquan 
Published: April 2003

AbstractThe effect of aluminium stearate on the rheological behavior of ultra‐high molecular weight polyethylene (UHMWPE) semidilute solutions with paraffin oil as the solvent has been investigated. Adding aluminium stearate to paraffin oil can prevent the spinning solution from adhering to the pipe or screw, greatly improving the flow behavior of UHMWPE solutions. The geometric sizes of spinnerette hole, such as length–diameter ratio L/D and entrance angle of a capillary, also affect the flow behavior of the spinning solution. The calculated first normal stress difference σ11 − σ22 and the Bagley‐end correction e from experimental data show that the elastic effect on spinning solutions in flow is quite large, although the shear rate is below 20 s−1.
Polymer characterization by thermal field flow fractionation with a continuous viscosity detector
Authors: Kirkland J. J. , Rementer S. W. , Yau W. W. 
Published: April 2003

AbstractA sensitive flow viscometer detector has been successfully used with time‐delay, exponential‐decay thermal field flow fractionation (TDE‐TFFF) to produce unique information on polymers. TFFF with a concentration‐dependent detector (e.g., refractometer) and a differential capillary viscometer is unable to produce a universal calibration plot that eliminates the necessity of polymer standards for accurate molecular‐weight calibration. However, this system directly provides valuable information on the inherent (or intrinsic) viscosity distribution of polymers. Absolute intrinsic viscosity values are measured by TFFF without the need of calibration. Detailed TFFF/inherent‐viscosity distribution profiles uniquely describe individual sample differences and are not affected by the experimental conditions used in TFFF separations. These viscosity distributions should be very useful in polymer characterization, since they are closely correlated with polymer end‐use and solution properties, as well as to polymer molecule weight.
Studies on the polyblends of poly(vinyl chloride) with various methacrylate copolymers, melt rheological properties. II
Authors: Saroop U. K. , Sharma K. K. , Jain K. K. , Misra Ashok , Maiti S. N. 
Published: April 2003

AbstractStudies have been made on the melt rheological properties of poly(vinyl chloride) (PVC) with copolymers of methyl methacrylate (MMA) and methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), and 2‐ethyl hexyl acrylate (EHA) at a blending ratio of 80:20. Effect of blend composition on shear stress–shear rate, melt viscosity, melt elasticity, and extrudate distortion have been studied. A significant decrease in the melt viscosity is observed on incorporation of low Tg, acrylate copolymers such as those with BA and EHA, thereby reducing the processing temperature. First normal stress and die swell ratio also decreases with an increase in the side chains of acrylate copolymer. PVC blended with P(MMA‐co‐BA) and P(MMA‐co‐EHA) is sensitive to both temperature and shear stress.
Studies on binary and ternary blends of polypropylene with ABS and LDPE. I. Melt rheological behavior
Authors: Gupta A. K. , Jain A. K. , Maiti S. N. 
Published: April 2003

AbstractStudies are presented on melt rheological properties of binary blend of polypropylene (PP) and acrylonitrile–butadiene–styrene terpolymer (ABS), and ternary blend of PP, ABS, and low‐den‐sity polyethylene (LDPE). Data obtained in capillary rheometer are presented to describe the effect of blending ratio, shear stress, and shear rate on flow properties, melt viscosity, and melt elasticity. At a blend composition corresponding to 10 wt % ABS content, both binary and ternary blends show maximum in melt viscosity accompanied by minimum in melt elasticity. Pseudoplasticity of the melt decreases with increasing ABS content. In ternary blends, LDPE facilitates the flow at low LDPE contents and obstructs the flow at high LDPE contents. Scanning electron microscopic studies are also presented to illustrate the state of dispersion and its variation with blend composition.
Higher aluminum trialkyls and magnesium aluminum alkyls as components of zioegler–natta catalysts
Authors: Gaponik L. V. , Antipova A. M. , Morozova T. K. , Mardykin V. P. 
Published: April 2003

AbstractMagnesium aluminum alkyls containing higher (C4–C10) radical swere studied as components of Ziegler–Natta catalysts in styrene polymerization. The effects of alkyl radical length and MgR2 contents in the components mentioned on the degree of TiCl4 reduction and sterospecific activity of the catalysts were investigated. The components studied exdhibited high reducing (for TiCl4) and catalytic a tivities. Moleculear weight of the synthesized isotactic polystyrene was abnormally high.
Radiation grafting of α,β,β‐trifluorostyrene onto poly(ethylene‐tetrafluoroethylene) film by preirradiation method. II. Properties of cation‐exchange membrane obtained by sulfonation and hydrolysis of the grafted film
Authors: Momose Takashi , Yoshioka Hiroko , Ishigaki Isao , Okamoto Jiro 
Published: April 2003

AbstractA Study was made on certain properties of the cation‐exchange membranes obtained by the preirradiation grafting of α,β,β‐trifluorostyrene (TFS) noto poly(ethylene‐tetrafluoroethylene) (ETFE), followed by sulfonation and hydrolysis of the grafted film. Swelling, water uptake, electric conductivity, and transport number of the membranes were measured as a function of ino‐exchange capacity. Thermal and chemical stability were also investigated. These properties were found to be mainly dependent on ion‐exchange capacity. The stable membrane properties were established due to a homogeneous ion‐exchange group distribution in the membrane, as confirmed by x‐ray imcroscopy analysis of the membrane cross sections. In addition, the membranes showed good electrochemical, thermal, and chemical properties, and were found to be scceptable for practical use as cation‐exchange membranes.
Preparation by suspension polymerization of porous beads for enzyme immobilization
Authors: Skovby Michael H. B. , Kops Jørgen 
Published: April 2003

AbstractPorous beads have been prepared by suspension polymerization of acrylic monomers and divinyl benzene in the presence of a porogen. The porosity varies greatly with the polymer composition, with the amount and type of porogen and with the conditions for the preparation. The enzyme binding capacity and activity has been determined for a lipase. The best results are found for crosslinked poly(methyl methacrylate) beads while other polyacrylates are less effective. Compositions based on poly(methacrylic acid) are not suitable for enzyme binding.
Influence of dimethyl sulfoxide on the kinetics of the graft copolymerization of acrylonitrile onto the jute fibers initiated by ceric ion
Authors: Das N. R. , Nayak N. C. , Das H. K. , Mishra S. N. , Singh B. C. 
Published: April 2003

AbstractA study of the influence of dimethyl sulfoxide (DMSO) on the graft copolymerization of acrylonitrile (AN) onto jute fiber using ceric ion has been made. The effect of concentrations of monomer, Ce(IV) and DMSO on graft yield have been studied. Besides, the effect of time, temperature, acid, and the amount of jute fiber on graft yield has been investigated. On the basis of experimental findings, a reaction mechanism has been proposed and optimum condition for effective grafting has been suggested.
Morphological studies on the blends of poly(butylene terephthalate) and bisphenol‐A polycarbonate
Authors: Halder R. S. , Joshi Mangala , Misra A. 
Published: April 2003

AbstractThe morphology of the blends of poly(butylene terephthalate) (PBT) and bisphenol‐A polycarbonate (PC) crystallized from the melt were studied by density measurement and small angle light scattering techniques. Rate of crystallization of these blends was found to be slower with increasing amount of PC. The Avrami exponent n for the blends was calculated and related to the shape of superstructures formed. Hv and Vv scattering patterns as seen by small angle light scattering were analyzed to determine the nature, shape, and size of the superstructures. The changes in the superstructure formation with increasing amount of PC in these blends have been analyzed.
Investigations on the curing of epoxides with phthalic anhydride
Authors: Steinmann Bettina 
Published: April 2003

AbstractThe anhydride curing of epoxides was studied by performing copolymerizations of epichlorohydrin, phenyl glycidyl ether (PGE), or bisphenol‐A‐diglycidyl ether (BADGE) with phthalic anhydride (PSA). As initiators, tertiary amines or ammonium salts were used. In the case of epichlorohydrin, linear polyesters were obtained at 100°C. At higher temperatures (140–160°C), a side reaction of the CH2Cl group took place which caused branching and partial crosslinking of the polymer. The reaction of phenyl glycidyl ether with phthalic anhydride gave linear, strongly alternating copolymers at temperatures of 120–160°C. Molecular weights (M¯n) were in the range of 4000–87,000, depending on the purity of the starting materials and the initiator used. The reaction of the diepoxide BADGE with phthalic anhydride yielded highly crosslinked products. Their crosslink densities (which correlate with the glass transition temperature Tg). however, did not show the same dependence on initiator and purity of the starting materials as the molecular weights of the linear polyesters obtained by the “model reaction” of PGE with PSA. Possible reasons for this effect are discussed.
Study and control of phase morphology in liquid crystal polyester–poly(alkylene terephthalate) blends
Authors: Croteau J. ‐F. , Laivins G. V. 
Published: April 2003

AbstractScanning electron microscopy (SEM) reveals that the morphologies of poly(hexamethylene terephthalate) (PHMT) and poly(p‐oxybenzoate co‐ethylene terephthalate) (LCP6/4) blends are biphasic. When LCP6/4 is the minor component, liquid crystalline domains are embedded in the matrix. The reaction in the melt between the polymers apparently increases the adhesion of the matrix to the embedded domains. As the reaction proceeds, the chemical composition of the matrix progressively becomes modified. High reaction temperatures, small particle size, mixing coupled with particle dispersion and high LCP6/4 content in the mixture promote the melt reaction and decrease the PHMT content in the polymer formed. At 260°C, the coaddition of di‐n‐octadecyl phosphite (DNOP) at a 2% weight fraction with PHMT and LCP6/4 inhibits the reaction between the polymers for 2 h.
Hollow fiber membranes spun from lewis acid : Base complexes. I. Structure determination by oxygen plasma ablation
Authors: Fritzsche A. K. , Cruse C. A. , Kesting R. E. , Murphy M. K. 
Published: April 2003

AbstractThe structures of polysulforne hollwo fiber membranes, spun from the propionic acid : N‐meth‐ylpyrrolidone complex and from a formylpiperidine/formamide mixture were investigated as a function of progressive surface removal with an oxygen plasma. Oxygen plasma ablation experiments were performed on both unexposed and isopentanetreated hollow fiber membrances. Pure gas permeation rates were obtained on these samples as well as oxygen plasma etched samples which were then subsequently coated with polydimethyl‐siloxane from an isopentane solution. The results show that the hollow fiber membrane spun from the propionic acid : N‐methylpyrrolidone complex has both a thinner active separating layer and a thinner skin than the polysulfone hollow fiber membrane spun from the formylpiperidine/formamide mixture. Also, the resistance to flow of the porous substrate of the complex spun hollow fiber membrane is significantly less than that of the polysulfone hollow fiber membrane spun from the mixture. Therefore, the substrate of the PA : NMP complex spun hollow fiber membrane has greater porosity and less tortuosity than its FP/FA congener. The oxygen plasma ablation results and the scanning electron micrographs demonstrate a nonequivalence between the active separating layer and the microscopically observable skin of the hollow fiber membrane. It is believed that membranes prepared from Lewis acid : base complex solvents possess a porous substructure and a nonuniform (graded‐density) skin which consists of a very thin active separating layer whose effective thickness varies depending upon the gases to be separated and a thin less dense transition layer, which may contain pores whose sizes are below the limits of resolution by SEM. Both are components of the microscopically observable skin. Membranes possessing this structure belong to the trilayer class of integrally skinned membranes. If membranes are so fabricated that the density gradient in the active separating layer approaches zero, a bilayer membrane with a porous substructure and a thin skin of uniform density results. Membranes prepared from conventional solvent/nonsolvent mixtures, i.e., formylpiperidine/formamide, exhibit a diminished density gradient in the skin approximating the bilayer model.
Purification of styrene for anionic polymerization
Authors: Priddy Duane B. , Pirc Michael 
Published: April 2003

AbstractAnionic polymerization of styrene in CSTR processes demands monomers which are highly pure. Lithium aluminum hydride (LAH) is a highly reactive material which reacts with the impurities in styrene that interfere with anionic polymerization. The LAH/impurity reaction products are not compatible with anionic polymerization and therefore must be isolated or removed from the styrene before polymerization. This problem is most readily solved by supporting the LAH on ion exchange resin beads such that the impurity reaction products are chemically bound to the support. We have demonstrated the preparation of > 50 mol of polystyrene/mol of n‐butyl lithium by passing the polymeization feed through a column filled with LAH/ion exchange resin. This represents > 10‐fold improvement in yield (based on n‐butyl lithium) over previously described feed purification techniques.
Preparation and properties of a series of thermotropic liquid crystalline copolyesters
Authors: Kim Han Do , Paul D. R. 
Published: April 2003

AbstractA series of thermotropic liquid crystalline copolyesters were prepared by melt polymerization using p‐hydroxybenzoic acid (HBA) and terephthalic acid (TPA) as mesogenic monomers, poly(ethylene terephthalate) (PET) to give a flexible linkage, and 1,4‐dihydroxynaphthalene (1,4‐DHN) as a dissymmetrical monomer. The composition of these monomers was varied as a means of manipulating processing temperature, morphology, and properties. Copolyesters with inherent viscosities near 0.7 that were melt processible in the temperature range of 200–300°C were obtained. The glass transition, thermal degradation, and melting temperatures, and crystal size all increased with increasing mesogenic unit content. The heterogeneous structure consisting of a PET‐rich phase and a phase rich in mesogenic units was observed by SEM after chemical etching and by X‐ray diffraction analysis. Highly anisotropic melts were observed indicating the presence of a nematic mesophase. The thermotropic LC copolyesters exhibit unusually well developed and highly oriented fibrillar structure at the neck area when injection molded. The orientation developed during processing is very similar to those of short‐fiber‐filled polymer composites. The LC copolyesters commonly have three relaxations in the temperature range of −100–200°C. By dynamic mechanical thermal analysis at 10 Hz, the relaxation temperatures were found to increase with increasing content of mesogenic units and of 1,4‐DHN. For the temperature range of 25–120°C, the storage modulus of one of the members of this series were compared with Vectra (Celanese) and with Eastman PHB80, which have almost the same mesogenic contents. This new copolyester maintained its modulus until 80°C, while the modulus of Vectra decreased in two steps; a small depression at 40°C and then a large reduction at 85°C. PHB80 shows a large single transition at 50°C.
The rheooptical properties of polymer blends: Polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide)
Authors: Greener J. , Machell J. S. 
Published: April 2003

AbstractThe stress‐optical coefficients (SOCs) of miscible polystyrene (PS)/poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PRO) blends were measured in the melt state over a wide range of compositions. The flow birefringence measurements were performed with a slit die rheometer using a simplified procedure which eliminates the need to specify the distribution of extinction angles in the flow space. The SOC of the PS/PPO system at ∼Tg + 110°C follows a linear blending law and full optical compensation (SOC = 0) is observed at ∼61 wt% PS. This value is lower by ∼10% relative to values obtained by film stretching techniques. Measurements of SOC in the glassy state also yield linear dependence of SOC on composition but no compensation is obtained in this case because of the sign reversal in the SOC of PS in the glass transition range.
Changes in void content and free volume in fibers during heat setting and their influence on dye diffusion and mechanical properties
Authors: Murthy N. S. , Reimschuessel A. C. , Kramer V. 
Published: April 2003

AbstractThe contributions of the changes in porosity and free volume to the differences in the properties of dry and wet heat set fibers are analyzed. Nylon 6 fibers heat set in wet atmosphere (autoclave and Superba process) show a significantly higher small‐angle X‐ray scattering intensity between 0.5° and 1.5° (Cu Kα) relative to corresponding non‐heat‐set fibers, whereas the fibers heat set in dry atmosphere (Suessen process) do not. This scattering arises from the electron density contrast due to pores and free volume which lower the elctron density between the fibrils. The average diameter of the crystalline fibrils, as calculated from the Guinier analysis of diffuse scattering, increases from ca. 50 to 65 Å in all fibers upon heat setting. Additional scattering at much lower angles is attributed to aggregates of fibrils. Transmission electron microscopic studies of fibers stained by AgI, through I2/methanol/AgNO3 treatment, suggest that as AgI crystallizes in a dendritic network along the paths opened up by the diffusion of iodine, it brings about large structural changes in the polymer; this process reveals defects and latent diffusion paths in the fiber. The dendritic structures of AgI are more extensive in wet heat set fibers than in dry heat set and non‐heat‐set fibers. The ordering within the crystalline domains, the interlamellar spacing, and the density of the fiber increase during both wet and dry processes. The role of these changes in the structure and the morphology of the fibers on the dyeing and ozone fading behavior, and on the strength and the modulus of the fibers, are discussed.
A sphere buoyant in a dilute polymer solution
Authors: Grisafi S. 
Published: April 2003

AbstractThe density and pressure fields of a dilute polymer solution are nonuniform at the surface of a small sphere even when there is no fluid motion. The polymer solution is modeled by an ensemble of Hookean dumbbells. A hard core potential is assumed as the only interaction between the sphere and the macromolecules. The pressure field about the sphere is transversely isotropic. The perpendicular component of the pressure at the interface is greater than the isotropic pressure in the bulk of the fluid. The parallel component of the pressure at the interface is less than the bulk isotropic pressure. The surface adsorption (cf., surface pressure) and the film thickness vary with a parameter that is the ratio of the sphere radius, a, to the root mean square extension of the dumbbells, R0. The spherical results coincide with the plane wall results for a/R0 greater than approximately 100.
Permeation of CO2 through polyurethane
Authors: Xiao H. , Ping Z. H. , Xie J. W. , Yu T. Y. 
Published: April 2003

AbstractThe permeability of CO2 through polyurethane was investigated. It is found that the permeability increases with the decrease of hard segment content and the increase of soft segment length; however, no change of activation energy is involved. The permeability increases with the elevation of annealing temperature. The temperature dependence of permeability observes the Arrhenius equation at temperatures below 60–80°C, but it deviates at temperatures above this range. This deviation would be attributed to the increase of mixing of hard and soft segments as a result of the dissociation of short‐range order in hard segment domains.
Multiple transitions in a dimethacrylate network
Authors: Wilson T. W. 
Published: April 2003

AbstractTriethylene glycol dimethacrylate, TEGDM, was cured to various dose levels (0.15–2.0 Mrad) by γ‐irradiation at 40°C and its dynamic mechanical properties were evaluated. The resultant products had up to four transition phenomena dependent upon dose. The highest temperature transition (IV) was due to the ultimate glass transition. Transition III (ca. 40°C) was due to additional reaction occuring just above the cure temperature. Transition 1 (ca. ‐60°C) occurred at low doses and was associated with residual monomer. Transition II (ca. ‐10°C) is due to association of (CH2CH2O) units in TEGDM monomer, and the associated regions persist in the crosslinked polymer.
Effect of internal lewis bases on recrystallized MgCl2–TiCl4 catalysts for polypropylene
Authors: Kang Kyung‐Suk , Ok Myung‐Ahn , Ihm Son‐Ki 
Published: April 2003

AbstractThe effect of different Lewis bases in TiCl4 catalysts supported on MgCl2, which was modified by the recrystallization method, has been investigated in terms of activity, selectivity, and morphology. Ethyl benzoate (EB) and 2,2,6,6‐tetramethylpiperidine (TMPip) were tested as the internal Lewis bases. Propylene polymerizations were performed at 50°C and 7 atm, using Al(C2H5)3 as co‐catalyst and TMPip as external modifier. Both supports and catalysts were characterized by BET, X‐ray, SEM, and other techniques. It was found that the electron donor plays an important role in the recrystallization step of MgCl2 from alcoholic MgCl2 solution. Ethyl benzoate was the more effective internal donor leading to the porous, free‐flowing, and stable high‐activity catalyst, while TMPip was not so effective as internal donor owing to its decomposition by SiCl4 during the support preparation. From short time polymerization kinetics, EB was found to increase both the values of the active site concentration ([C*]) and the propagation rate constant (kp). Comparison with the ball‐milled catalyst has been made in view of the morphology. The morphology of the polymers formed with the recrystallized catalysts was the globule‐like structure, while that with the milled catalyst was the broken structure due to its low surface area.