bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic simulation of primary particle‐size distribution in vinyl chloride polymerization
Authors: Kiparissides C. , Achilias D. S. , Chatzi E. 
Published: April 2003

AbstractIn the suspension polymerization of vinyl chloride, colloidally stable primary particles are formed inside the polymerizing monomer droplets. The nucleation, growth, and aggregation of these particles are responsible for the formation of the internal particle morphology and associated properties, such as pore‐size distribution, specific surface area, and plasticizer uptake. In the present investigation, a population balance model is derived describing the time evolution of the primary particle‐size distribution in the polymerizing monomer droplets. The resulting integrodifferential equation accounts for the coalescence rate of electrically charged colloidal primary particles through the use of the Fuchs modification of the extended Smoluckowski coagulation equation. Simulation studies were carried out to determine both the effects of the model parameters and to afford a direct comparison of model predictions with experimental measurements of the time evolution of the primary particle‐size distribution. The dependence of the total number and of the mean diameter of the primary particles on several process variables (i.e., the ionic strength of the medium, total particle charge, temperature, initial initiator concentration, and agitation rate) is quantitatively analyzed. Finally, the predictive capability of the present model is demonstrated by a direct comparison of model predictions with the experimental data of Willmouth et al. and Törnell and Uustalu. © 1994 John Wiley & Sons, Inc.
Attempted synthesis of multiblock copolymers of butadiene, styrene, and α‐methylstyrene: Effect of polar additives on copolymerizations
Authors: Wang L. S. , Phalip P. , Favier J.‐C. , Sigwalt P. 
Published: April 2003

AbstractOwing to the low Tg of polystyrene, the mechanical properties of polystyrene‐block‐poly‐butadiene‐block‐polystyrene (SBS) thermoplastic elastomers drop steeply above 60°C. To overcome this behavior, many research groups have considered the replacement of styrene (S) by α‐methylstyrene (MS). We also attempted the synthesis of copolymers with a central polybutadiene (poly B) block and rigid blocks consisting of polystyrene (poly S) and poly(α‐methylstyrene) (poly MS) blocks. Starting from a dilithium initiator, difunctional poly B's with low 1,2 content (10%) were prepared and toluene was added. After addition of a small amount of styrene, MS was added in the presence of a 15% (in vol) of THF at T ≤ −40°C. The copolymers did not have the expected structure and poor mechanical properties resulted, which were, however, still measurable at 120°C. These results probably resulted from secondary reactions involving the MS carbanions. To identify these reactions and to control the polymer structure, the synthesis of multiblock copolymers was carried out with a monofunctional polybutadienyllithium to which were added successively S and MS (in a mixture of hexane and benzene as solvent). MS was added at low temperature in the presence of small amounts of THF or at room temperature after addition of TMEDA. These attempts were unsuccessful, the copolymer being always multimodal as a result of unwanted coupling reactions involving terminal double bonds. The synthesis of elastomers using a coupling reaction of poly MS–poly S–poly B was also considered but the yield in poly B was low since termination reactions involving the polar additive occurred. © 1994 John Wiley & Sons, Inc.
Spherulite nucleation in blends of isotactic polypropylene with isotactic poly(butene‐1)
Authors: Bartczak Z. , Galeski A. , Pracella M. 
Published: April 2003

AbstractThe phase morphology and the influence of composition on the primary nucleation of isotactic polypropylene in isotactic polypropylene/isotactic poly(butene‐1) (iPP/iPB) blends were investigated by electron and light microscopy and small‐angle light scattering. It was found that iPP and iPB are miscible but the thermal treatment induces partial phase separation of components and the formation of iPP‐rich and iPB‐rich phases. The complete phase separation needs high temperatures and/or a long time of melt annealing. In samples crystallized isothermally at low undercooling the heterogeneous primary nucleation in blends is depressed as compared to plain iPP. In blends the less active heterogeneities lose their activity because of an increase of the energy barrier for critical size nucleus formation due to phase separation of blend components during crystallization. For the same reason the rate of homogeneous nucleation in blends decreases, as observed in samples crystallized at very high undercooling. At very high undercooling iPP and iPB are able to crystallize with similar rates, which results in the formation of a fraction of iPB spherulites in addition to iPP spherulites. Consequently the number of spherulites in the blend is larger than that in plain iPP, in spite of the decrease in the homogeneous nucleation rate of iPP in the blend. © 1994 John Wiley & Sons, Inc.
Temperature dependence of pH for solubilized collagen solutions
Authors: Matsushita Satoru , Deki Shigehito , Mizuhata Minoru , Sugita Masami , Kanaji Yukio 
Published: April 2003

AbstractThe temperature dependence of the pH for an acid‐soluble collagen in solution was measured, so that the pH largely increased in the temperature region including ca. 40°C of the thermal denaturation temperature. As the changes of the optical rotation, αD, and the electrical conductivity, σ, were observed in this temperature region, the change of the pH is due to the thermal denaturation of collagen. The differential curve of pH vs. t gave clear deflection points and a large peak at ca. 40°C. The thermal denaturation temperature, td, could be estimated from the peak temperature. The td obtained by the measurement of the αD, tdαD, decreased with the decrease in the heating rate and with the increase in the concentration of collagen. However, the td obtained through the measurement of the pH, tdpH, was independent of the variations of the heating rate and the concentration of collagen. These measurements were carried out for different kinds of collagens prepared by various methods. Some of them had one kind of peak; others had two kinds of peaks. The tdpH correlated with the tdαD for different kinds of collagen preparations. Therefore, the measurement of the temperature dependence of the pH was useful for the determination of the td. © 1994 John Wiley & Sons, Inc.
Electrical properties of diphenyldiacetylene annealed under elevated pressure
Authors: Kojima Yoshitsugu , Matsuoka Takaaki , Takahashi Hideroh 
Published: April 2003

AbstractA unique class of conjugated compounds composed of the derivative of condensed polycyclic aromatic compound with the phenyl group and diphenyldiacetylene oligomer was synthesized by annealing of diphenyldiacetylene under elevated pressure. The effect of annealing pressure on the conductivity of the compounds was studied. The total conductivity of the compound decreased with a decrease of frequency, approaching a constant value (dc conductivity: Cdc). The dc conductivity of the compound increased from below 10−15 to 10 S cm−1 with increasing annealing pressure. The dc conductivity of the oligomer was below 10−15 S cm−1 and that of the derivative increased from 10−8 to 10 S cm−1 with decreasing H/C (H/C:0.45–0.04). The conduction of the conjugated compound was electronic. The temperature coefficient of those dc conductivities was positive, with an approximately linear relation between In (CdcT0.5) and (1/T)0.25, where T is the temperature. The ac conductivities Cac were proportional to temperature and frequency f and had the following equation Cac = TfS, S = 0.67–0.75. These results showed that the conduction mechanism can be explained by the hopping in a manifold of states at the Fermi level. © 1994 John Wiley & Sons, Inc.
Thermally stimulated current and effect of annealing on the electrical properties of cellulose nitrate
Authors: Amin M. , Darwish K. A. , Mounir M. , Elez M. Abu 
Published: April 2003

AbstractThe investigated samples were of cellulose nitrate CA‐80‐15. The dc conductivity (σ) and the dielectric permittivity decreasd with increasing time of annealing. The activation energy is 0.46 eV in a temperature range from 298 to 385 K. The thermally stimulated current (TSC), JD, was measured. The maximum value of the TSC (Jm) increases with increasing the rate of heating and shifts slightly toward higher values of temperature. The activation energy (0.25 eV) is independent of the variation of the rate of heating. In addition, the peak positions for the constant rate of heating were unaffected by increasing the polarization time, but the maximum value of the current increases and the activation energy decreases. The dipolar relaxation time was calculated theoretically and studied as a function of temperature. © 1994 John Wiley & Sons, Inc.
Plasma polymerized membranes from organosilicon compounds for separation of oxygen over nitrogen
Authors: Matsuyama Hideto , Shiraishi Tomoyuki , Teramoto Masaaki 
Published: April 2003

AbstractPlasma polymerized membranes were prepared from octamethyltrisiloxane for the purpose of separation of O2 over N2. The obtained membrane consisted of plasma prepared polymer layer on top of a porous polyproplene substrate. The membrane polymerized under the mild plasma condition (low power input and high monomer flow rate) showed the high permeation rate. Selectivity, however, was hardly affected by the plasma conditions. The selectivity and permeation rate obtained were 2.6 and 2.5 × 10−10 kmol/(m2·s·Pa) (=7.5×10−4 cm3/(cm2·s·cmHg)), respectively. This high permeation rate was attributed to the use of the monomer with the long, flexible siloxane chain and the mild plasma condition. Moreover, the membranes were prepared from a series of monomers with different siloxane chain lenghts (methoxytrimethylsilane, hexamethyldisiloxane, and octamethyltrisiloxane), and from those with different alkyl chain lenghts (methoxytrimethylsilane, propoxytrimethylsilane, and hexyloxytrimethylsilane). As the siloxane chain lenghts of the starting monomers increased and the alkyl chain lengths decreased, the permeation rates of the corresponding polymers increased. The selectivities were nearly constant regardless of the difference in the starting monomer structures. The structures of the plasma prepared polymers were analyzed by XPS and IR measurements, and discussed in relation to the membrane efficiencies. © 1994 John Wiley & Sons, Inc.
Dynamic properties of short fiber–EPDM matrix composites as a function of strain amplitude
Authors: Ibarra L. 
Published: April 2003

AbstractThe dynamic properties of composite materials consisting of an ethylene–propylene rubber matrix (EPDM) and short polyester polyethylene‐terephthalate (PET) fiber vary with dynamic stress amplitude applied to the material. These variations support the statement that fiber treatment with 1,4‐carboxy‐sulphonyl‐diazide, which acts as a bridge between the fiber and the matrix and hence enhances the strength of the interface enabling it to resist greater strain applied to the composite and, as a consequence, yielding greater retention values of the storage modulus, measured longitudinally to preferential fiber orientation, E′L. By means of transversal measurements of the storage modulus, E′T, of these materials it is possible to determine a parameter b, which eventually indicates the degree of matrix–fiber bonding and which is consistently higher for materials filled with surface‐treated fiber. This enhanced phase adhesion is further confirmed by higher equivalent interfacial thickness values, ΔR, which, in addition, vary less with increasing dynamic strain amplitude. Finally dissipated energy variation or mechanical energy loss, Eloss, is studied as a function of fiber content and strain amplitude. Experimental findings show Eloss to increase with fiber content and strain amplitude, when measured at constant strain amplitude ϵ0, and to yield higher values for treated fiber samples. © 1994 John Wiley & Sons, Inc.
Polylactide. II. Discontinuous dry spinning–hot drawing preparation of fibers
Authors: Horáček I. , Kalíšek  
Published: April 2003

AbstractThe mechanical properties and morphology of poly(L‐lactide) fibers, prepared by the dry spinning–hot drawing process using different nonsolvent/chloroform spinning solutions, were studied in relation to fiber in vitro degradability. Acetone, methanol, ethanol, and cyclohexane were used as nonsolvents in the spinning mixture with as‐polymerized PLLA, i.e., PLLA containing 10% of residual L‐lactide. The tensile strength, structure, and degradability of obtained fibers were mainly governed by the nonsolvent volatility. Generally, the higher the volatility, the higher the strength, and the faster the degradation. The acetone/chloroform spinning system produced fiber with an increased degradation rate in comparison to the pure chloroform spinning system. © 1994 John Wiley & Sons, Inc.
Solid‐phase oxidation of polyethylene coatings on metals
Authors: Lin Dmitry G. 
Published: April 2003

AbstractThe paper considers the problem of solid‐phase oxidation for cases of polyethylene coatings applied onto active (copper) and passive (aluminum) substrates. Oxidation of PE coatings on copper, unlike that of PE coatings on aluminum, is shown to develop in two stages separated by a time period of autoinhibition. During this time period the concentration of carboxyl groups does not in fact change. In a similar manner copper‐containing compounds accumulate in the coating, which fact supports the relation between metal transfer and polymer oxidation processes. © 1994 John Wiley & Sons, Inc.
Influence of water uptake on the mechanical properties of jute fiber‐reinforced polypropylene
Authors: Karmaker A. C. , Hoffmann A. , Hinrichsen G. 
Published: April 2003

AbstractJute fiber‐reinforced polypropylene composites have been produced and characterized in order to investigate the influence of water on their mechanical properties. Being hydrophilic, jute fibers absorb a high amount of water causing swelling of fibers. On the other hand, the thermal shrinkage of polypropylene melt leaves some gaps between jute fibers and matrix material. We investigated whether these gaps could be filled by the swelling of wetted fibers. The fillup of these gaps would result in a higher shear strength between fibers and matrix during fracture. Our results suggest that swelling of jute fibers in a composite material can have positive effects on mechanical properties. © 1994 John Wiley & Sons, Inc.
Synthesis, properties, and morphology based on polyurethane and polymethyl methacrylate AB‐crosslinked copolymers
Authors: Zhang Liucheng , Pan Mingwang , Tai Huiwen , Li Xiucuo 
Published: April 2003

AbstractThe AB‐crosslinked copolymer was prepared as a transparent material from toluene diisocyanate (TDI) or hexamethane diisocyanate (HDI), triethylene glycol (TEG), hydroxyethyl methacrylate (HEMA), and methyl methacrylate (MMA). The optical transmission, impact resistance, thermal mechanical properties, and morphology of the copolymer were studied. The results indicate that this material has a microheterogeneous structure with the dispersed phase size no more than 0.1 μm. © 1994 John Wiley & Sons, Inc.
Thermal and structural analysis of heparin–PEO–PDMS–PEO–heparin pentablock copolymers
Authors: Kim Yong Joo , Sung Yong Kiel , Piao Ai Zhi , Grainger David W. , Okano Teruo , Kim Sung Wan 
Published: April 2003

AbstractABCBA‐type amphiphilic block copolymers comprising polydimethylsiloxane (PDMS), poly(ethylene oxide) (PEO), and heparin segments were synthesized by coupling reactions between end‐functionalized oligomers. These multiblock copolymers were characterized to examine bulk properties using 1H‐NMR, FTIR, end‐group analysis, and sulfur elemental analysis. Block copolymers were further characterized in bulk using differential scanning calorimetry and X‐ray diffraction measurements. The PDMS glass transition remains unchanged with increasing PEO content, indicating coexistence of pure PDMS with mixed phases. Furthermore, endothermic melting of the block copolymers shifts to higher temperatures and becomes more intense with increasing PEO molecular weight. Additionally, the crystallinity of the PEO segment in the block copolymers increases with increasing PEO molecular weight. The PEO melting endotherm peak shifts from near 318 to 323 K with annealing. In the cooling thermogram, the block copolymers exhibit two crystallization exotherms, one near 303 K and the other near 193 K, attributed to PEO and PDMS recrystallization and nucleation, respectively. © 1994 John Wiley & Sons, Inc.
Preparation of new synthetic hydrogels containing galactose, applicable in affinity chromatography
Authors: Alvarez C. , Bertorello H. , Strumia M. 
Published: April 2003

AbstractNew biospecific affinity chromatography adsorbents were prepared from epoxy reactive matrices with subsequent coupling of galactose as the ligand and were afterward characterized. Their usefulness in the sorption of peanut lectin, a protein specifically retained by the galactose residue, is reported. © 1994 John Wiley & Sons, Inc.
Composition control in emulsion copolymerization. I. Optimal monomer feed policies
Authors: Canu Paolo , Canegallo Stefano , Morbidelli Massimo , Storti Giuseppe 
Published: April 2003

AbstractThe problem of producing polymers with constant instantaneous composition in semibatch reactors has been addressed in the most general terms. A rigorous procedure for determining a priori the monomer feed policy that allows one to produce, with a minimum reaction time, a given amount of polymer, with constant instantaneous composition and complete monomer depletion, has been developed. The procedure involves the knowledge of only the monomer reactivity ratios and the interphase partition laws. Its practical implementation needs the on‐line monitoring of conversion. The reliability of the theoretical approach has been tested by comparison with the optimal policies obtained in the literature, for three different binary systems, as the result of various experimental iterative procedures. © 1994 John Wiley & Sons, Inc.
Compatibility and morphology studies of PPO multicomponent blends
Authors: Liang Borun , Pan Lihua 
Published: April 2003

AbstractThe compatibility and phase morphology of poly(phenylene oxide) (PPO) multicomponent blends with poly(ethylene terephthalate) (PET) and polystyrene (PS) were studied using differential‐scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM) methods. The effect of glycidyl methacrylate–styrene copolymer (GMS), as a compatibilizer, on the morphology of the PPO blends has also been studied in detail. The influence of the molecular weight of PET and the synergetic effect of the compatibilizers of GMS and phenoxy (PN) on the morphology were examined. The DSC and DMA results show that two distinct glass transitions corresponding to PET and PPO existed; however, the Tg of PPO shifts toward lower temperature region due to the addition of GMS and PS. The SEM results reveal that PET component exists as dispersed phases in the PPO matrix, while PS is miscible in the PPO matrix. A significant improvement of the compatibility was achieved for the PPO multicomponent blends because of the synergetic effect of GMS and phenoxy. © 1994 John Wiley & Sons, Inc.
Studies on a new water‐soluble sulfur‐containing cellulose derivative
Authors: Zeng Huiyang , Li Wei , Li Zhuomei 
Published: April 2003

AbstractA new sulfur‐containing cellulose derivative, carboxymethyl cellulose (CMC) xanthate (CMCX), has been prepared by the reaction of CMC with CS2 in 10–15% NaOH solution for 1 h. Degree of esterification (DE) of the product, determined by UV, may reach 3.3% by mole (or about 1.1% by weight). The product was water soluble. The stability of CMCX has been studied by UV, DSC, and TGA, and it was found that CMCX was more stable in the solid state than in solution. The precipitation of gold ion in dilute solution (10 μg Au · mL−1) by CMCX was very rapid, and the recovery efficiency of gold could reach 96% or higher. The optimum dosage was about 0.1 g CMCX for 10 mL 10 μg Au · mL−1 solution. © 1994 John Wiley & Sons, Inc.
Heat‐resistant polyimides and polyamides prepared from 2, 7‐diamino‐9‐dicyanomethylene‐fluorene
Authors: Diakoumakos Constantinos D. , Mikroyannidis John A. 
Published: April 2003

Abstract9‐Fluorenone was nitrated with fuming nitric acid to yield 2,7‐dinitro‐fluorenone (1). It was condensed with malononitrile in the presence of glacial acetic acid and a catalytic amount of piperidine to afford 2,7‐dinitro‐9‐dicyanomethylene‐fluorene (2). It was catalytically hydrogenated to the corresponding diamine (3). The latter was used as starting material for the preparation of new polyimides and polyamides bearing dicyanomethylene units. In addition, a bismaleimide was synthesized from the reaction of 3 with maleic anhydride and subsequent cyclodehydration of the intermediate bismaleamic acid. The FTIR spectra of polymers were in agreement with those of the synthesized model compounds. The polymers and bismaleimide yielded crosslinked resins upon curing at 300°C for 40 h in the presence of a catalytic amount of 4,4′‐diaminodiphenylmethane. They were stable up to 355–430°C in N2 or air and afforded anaerobic char yield of 52–57% at 800°C. © 1994 John Wiley & Sons, Inc.
Interpenetrating polymer networks. I. Photopolymerization of multiacrylate systems
Authors: Kaczmarek H. , Decker C. 
Published: April 2003

AbstractThe light‐induced polymerization of a triacrylate monomer (TMPTA) has been carried out in a polymer matrix to generate a semi‐interpenetrating polymer network (IPN). The reaction kinetics was followed by IR spectroscopy for the various polymer binders studied: poly(vinyl chloride) (PVC), poly(methyl methacrylate), polystyrene, and crosslinked polyurethane. Under intense illumination, crosslinking occurred extensively within a fraction of a second, with formation of a hard and highly resistant polymer material. These semi‐IPNs were found to be essentially insoluble in the organic solvents, thus indicating that the acrylate network is grafted onto the polymer matrix, probably because of an efficient chain transfer process. The monomer and photoinitiator concentration, as well as the light intensity were shown to have a great influence on both the rate of polymerization and the final degree of conversion. By using an acylphosphine oxide photoinitiator, PVC–;TMPTA blends have been cured within a few minutes in an accelerated QUV‐A weatherometer, which emits low‐intensity UV radiation similar to sunlight. © 1994 John Wiley & Sons, Inc.
Sorption, desorption, diffusion, and permeation of aliphatic alkanes into santoprene thermoplastic rubber
Authors: Aminabhavi Tejraj M. , Phayde Hemant T. S. 
Published: April 2003

AbstractThe molecular transport characteristics of Santoprene rubber in the presence of n‐alkanes, cyclohexane, 2,2,4‐trimethylpentane, and 1,2,3,4‐tetrahydronaphthalene at 25, 40, 55, and 70°C have been studied using a sorption gravimetric technique. From the sorption and desorption studies, the diffusion coefficients have been calculated and used in the discussion of the transport results. It was observed that these data depend on the size of the penetrants. Furthermore, efforts were made to evaluate the permeation coefficients, molar mass between crosslinks, and the kinetic rate constants. These data showed a systematic dependence on the penetrant size. Activation parameters for the process of diffusion and permeation have been calculated from the temperature dependence of the transport coefficients. © 1995 John Wiley & Sons, Inc.